[RFC PATCH 0/8] TTM shrinker helpers and xe buffer object shrinker

[RFC PATCH 0/8] TTM shrinker helpers and xe buffer object shrinker

[Thomas Hellström]

This series implements TTM shrinker / eviction helpers and an xe bo
shrinker. It builds on two previous series. First

https://www.mail-archive.com/dri-devel@lists.freedesktop.org/msg484425.html

for patch 1-4, which IMO still could be reviewed and pushed as a
separate series.

Second the previous TTM shrinker series

https://lore.kernel.org/linux-mm/b7491378-defd-4f1c-31e2-29e4c77e2d67@amd.com/T/

Where the comment about layering
https://lore.kernel.org/linux-mm/b7491378-defd-4f1c-31e2-29e4c77e2d67@amd.com/T/#ma918844aa8a6efe8768fdcda0c6590d5c93850c9

now addressed, and this version also implements shmem objects for backup
rather than direct swap-cache insertions, which was used in the previuos
series. It turns out that with per-page backup / shrinking, shmem objects
appears to work just as well as direct swap-cache insertions with the
added benefit that was introduced in the previous TTM shrinker series to
avoid running out of swap entries isn't really needed.

In any case, patch 1-4 are better described in their separate series.
(RFC is removed for those).

Patch 5 could in theory be skipped but introduces a possibility to easily
add or test multiple backup backends, like the direct swap-cache
insertion or even files into fast dedicated nvme storage for for example.

Patch 6 introduces helpers in the ttm_pool code for page-by-page shrinking
and recovery. It avoids having to temporarily allocate a huge amount of
memory to be able to shrink a buffer object. It also introduces the
possibility to immediately write-back pages if needed, since that tends
to be a bit delayed when left to kswapd.

Patch 7 introduces a LRU walk helper for eviction and shrinking. It's
currently xe-only but not xe-specific and can easily be moved to TTM when
used by more than one driver or when eviction is implemented using it.

Patch 8 introduces a helper callback for shrinking (Also ready to be
moved to TTM) and an xe-specific shrinker implementation.

Testing:
ATM I don't think we have good tests to cover the shrinking functionality
The series has been tested with a hack that continously creates
TTM_TT buffer objects until system memory and swap space is exhausted,
and then reads them back and frees them. However, these tests
seem to be very slow.
Ideally a similar test on a machine with very fast solid state or
similar storage should be set up. Ideally also verifying content
preservation.

Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: <dri-devel@lists.freedesktop.org>

Thomas Hellström (8):
  drm/ttm: Allow TTM LRU list nodes of different types
  drm/ttm: Use LRU hitches
  drm/ttm, drm/amdgpu, drm/xe: Consider hitch moves within bulk sublist
    moves
  drm/ttm: Allow continued swapout after -ENOSPC falure
  drm/ttm: Add a virtual base class for graphics memory backup
  drm/ttm/pool: Provide a helper to shrink pages.
  drm/xe, drm/ttm: Provide a generic LRU walker helper
  drm/xe: Add a shrinker for xe bos

 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c |   4 +
 drivers/gpu/drm/ttm/Makefile           |   2 +-
 drivers/gpu/drm/ttm/ttm_backup_shmem.c | 137 +++++++++
 drivers/gpu/drm/ttm/ttm_bo.c           |   1 +
 drivers/gpu/drm/ttm/ttm_device.c       |  33 ++-
 drivers/gpu/drm/ttm/ttm_pool.c         | 391 ++++++++++++++++++++++++-
 drivers/gpu/drm/ttm/ttm_resource.c     | 231 ++++++++++++---
 drivers/gpu/drm/ttm/ttm_tt.c           |  34 +++
 drivers/gpu/drm/xe/Makefile            |   2 +
 drivers/gpu/drm/xe/xe_bo.c             | 123 ++++++--
 drivers/gpu/drm/xe/xe_bo.h             |   3 +
 drivers/gpu/drm/xe/xe_device.c         |   8 +
 drivers/gpu/drm/xe/xe_device_types.h   |   2 +
 drivers/gpu/drm/xe/xe_shrinker.c       | 237 +++++++++++++++
 drivers/gpu/drm/xe/xe_shrinker.h       |  18 ++
 drivers/gpu/drm/xe/xe_ttm_helpers.c    | 224 ++++++++++++++
 drivers/gpu/drm/xe/xe_ttm_helpers.h    |  63 ++++
 drivers/gpu/drm/xe/xe_vm.c             |   4 +
 include/drm/ttm/ttm_backup.h           | 136 +++++++++
 include/drm/ttm/ttm_device.h           |   2 +
 include/drm/ttm/ttm_pool.h             |   4 +
 include/drm/ttm/ttm_resource.h         |  96 +++++-
 include/drm/ttm/ttm_tt.h               |  19 ++
 23 files changed, 1683 insertions(+), 91 deletions(-)
 create mode 100644 drivers/gpu/drm/ttm/ttm_backup_shmem.c
 create mode 100644 drivers/gpu/drm/xe/xe_shrinker.c
 create mode 100644 drivers/gpu/drm/xe/xe_shrinker.h
 create mode 100644 drivers/gpu/drm/xe/xe_ttm_helpers.c
 create mode 100644 drivers/gpu/drm/xe/xe_ttm_helpers.h
 create mode 100644 include/drm/ttm/ttm_backup.h

-- 
2.44.0

[PATCH 1/8] drm/ttm: Allow TTM LRU list nodes of different types

[Thomas Hellström]

To be able to handle list unlocking while traversing the LRU
list, we want the iterators not only to point to the next
position of the list traversal, but to insert themselves as
list nodes at that point to work around the fact that the
next node might otherwise disappear from the list while
the iterator is pointing to it.

These list nodes need to be easily distinguishable from other
list nodes so that others traversing the list can skip
over them.

So declare a struct ttm_lru_item, with a struct list_head member
and a type enum. This will slightly increase the size of a
struct ttm_resource.

v2:
- Update enum ttm_lru_item_type documentation.

Cc: Christian König <christian.koenig@amd.com>
Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
Cc: <dri-devel@lists.freedesktop.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/ttm/ttm_device.c   | 13 ++++--
 drivers/gpu/drm/ttm/ttm_resource.c | 70 ++++++++++++++++++++++--------
 include/drm/ttm/ttm_resource.h     | 51 +++++++++++++++++++++-
 3 files changed, 110 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index 76027960054f..f27406e851e5 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -270,17 +270,22 @@ EXPORT_SYMBOL(ttm_device_fini);
 static void ttm_device_clear_lru_dma_mappings(struct ttm_device *bdev,
 					      struct list_head *list)
 {
-	struct ttm_resource *res;
+	struct ttm_lru_item *lru;
 
 	spin_lock(&bdev->lru_lock);
-	while ((res = list_first_entry_or_null(list, typeof(*res), lru))) {
-		struct ttm_buffer_object *bo = res->bo;
+	while ((lru = list_first_entry_or_null(list, typeof(*lru), link))) {
+		struct ttm_buffer_object *bo;
+
+		if (!ttm_lru_item_is_res(lru))
+			continue;
+
+		bo = ttm_lru_item_to_res(lru)->bo;
 
 		/* Take ref against racing releases once lru_lock is unlocked */
 		if (!ttm_bo_get_unless_zero(bo))
 			continue;
 
-		list_del_init(&res->lru);
+		list_del_init(&bo->resource->lru.link);
 		spin_unlock(&bdev->lru_lock);
 
 		if (bo->ttm)
diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
index be8d286513f9..7aa5ca5c0e33 100644
--- a/drivers/gpu/drm/ttm/ttm_resource.c
+++ b/drivers/gpu/drm/ttm/ttm_resource.c
@@ -69,8 +69,8 @@ void ttm_lru_bulk_move_tail(struct ttm_lru_bulk_move *bulk)
 			dma_resv_assert_held(pos->last->bo->base.resv);
 
 			man = ttm_manager_type(pos->first->bo->bdev, i);
-			list_bulk_move_tail(&man->lru[j], &pos->first->lru,
-					    &pos->last->lru);
+			list_bulk_move_tail(&man->lru[j], &pos->first->lru.link,
+					    &pos->last->lru.link);
 		}
 	}
 }
@@ -83,14 +83,38 @@ ttm_lru_bulk_move_pos(struct ttm_lru_bulk_move *bulk, struct ttm_resource *res)
 	return &bulk->pos[res->mem_type][res->bo->priority];
 }
 
+/* Return the previous resource on the list (skip over non-resource list items) */
+static struct ttm_resource *ttm_lru_prev_res(struct ttm_resource *cur)
+{
+	struct ttm_lru_item *lru = &cur->lru;
+
+	do {
+		lru = list_prev_entry(lru, link);
+	} while (!ttm_lru_item_is_res(lru));
+
+	return ttm_lru_item_to_res(lru);
+}
+
+/* Return the next resource on the list (skip over non-resource list items) */
+static struct ttm_resource *ttm_lru_next_res(struct ttm_resource *cur)
+{
+	struct ttm_lru_item *lru = &cur->lru;
+
+	do {
+		lru = list_next_entry(lru, link);
+	} while (!ttm_lru_item_is_res(lru));
+
+	return ttm_lru_item_to_res(lru);
+}
+
 /* Move the resource to the tail of the bulk move range */
 static void ttm_lru_bulk_move_pos_tail(struct ttm_lru_bulk_move_pos *pos,
 				       struct ttm_resource *res)
 {
 	if (pos->last != res) {
 		if (pos->first == res)
-			pos->first = list_next_entry(res, lru);
-		list_move(&res->lru, &pos->last->lru);
+			pos->first = ttm_lru_next_res(res);
+		list_move(&res->lru.link, &pos->last->lru.link);
 		pos->last = res;
 	}
 }
@@ -121,11 +145,11 @@ static void ttm_lru_bulk_move_del(struct ttm_lru_bulk_move *bulk,
 		pos->first = NULL;
 		pos->last = NULL;
 	} else if (pos->first == res) {
-		pos->first = list_next_entry(res, lru);
+		pos->first = ttm_lru_next_res(res);
 	} else if (pos->last == res) {
-		pos->last = list_prev_entry(res, lru);
+		pos->last = ttm_lru_prev_res(res);
 	} else {
-		list_move(&res->lru, &pos->last->lru);
+		list_move(&res->lru.link, &pos->last->lru.link);
 	}
 }
 
@@ -154,7 +178,7 @@ void ttm_resource_move_to_lru_tail(struct ttm_resource *res)
 	lockdep_assert_held(&bo->bdev->lru_lock);
 
 	if (bo->pin_count) {
-		list_move_tail(&res->lru, &bdev->pinned);
+		list_move_tail(&res->lru.link, &bdev->pinned);
 
 	} else	if (bo->bulk_move) {
 		struct ttm_lru_bulk_move_pos *pos =
@@ -165,7 +189,7 @@ void ttm_resource_move_to_lru_tail(struct ttm_resource *res)
 		struct ttm_resource_manager *man;
 
 		man = ttm_manager_type(bdev, res->mem_type);
-		list_move_tail(&res->lru, &man->lru[bo->priority]);
+		list_move_tail(&res->lru.link, &man->lru[bo->priority]);
 	}
 }
 
@@ -196,9 +220,9 @@ void ttm_resource_init(struct ttm_buffer_object *bo,
 	man = ttm_manager_type(bo->bdev, place->mem_type);
 	spin_lock(&bo->bdev->lru_lock);
 	if (bo->pin_count)
-		list_add_tail(&res->lru, &bo->bdev->pinned);
+		list_add_tail(&res->lru.link, &bo->bdev->pinned);
 	else
-		list_add_tail(&res->lru, &man->lru[bo->priority]);
+		list_add_tail(&res->lru.link, &man->lru[bo->priority]);
 	man->usage += res->size;
 	spin_unlock(&bo->bdev->lru_lock);
 }
@@ -220,7 +244,7 @@ void ttm_resource_fini(struct ttm_resource_manager *man,
 	struct ttm_device *bdev = man->bdev;
 
 	spin_lock(&bdev->lru_lock);
-	list_del_init(&res->lru);
+	list_del_init(&res->lru.link);
 	man->usage -= res->size;
 	spin_unlock(&bdev->lru_lock);
 }
@@ -471,14 +495,16 @@ struct ttm_resource *
 ttm_resource_manager_first(struct ttm_resource_manager *man,
 			   struct ttm_resource_cursor *cursor)
 {
-	struct ttm_resource *res;
+	struct ttm_lru_item *lru;
 
 	lockdep_assert_held(&man->bdev->lru_lock);
 
 	for (cursor->priority = 0; cursor->priority < TTM_MAX_BO_PRIORITY;
 	     ++cursor->priority)
-		list_for_each_entry(res, &man->lru[cursor->priority], lru)
-			return res;
+		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
+			if (ttm_lru_item_is_res(lru))
+				return ttm_lru_item_to_res(lru);
+		}
 
 	return NULL;
 }
@@ -497,15 +523,21 @@ ttm_resource_manager_next(struct ttm_resource_manager *man,
 			  struct ttm_resource_cursor *cursor,
 			  struct ttm_resource *res)
 {
+	struct ttm_lru_item *lru = &res->lru;
+
 	lockdep_assert_held(&man->bdev->lru_lock);
 
-	list_for_each_entry_continue(res, &man->lru[cursor->priority], lru)
-		return res;
+	list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
+		if (ttm_lru_item_is_res(lru))
+			return ttm_lru_item_to_res(lru);
+	}
 
 	for (++cursor->priority; cursor->priority < TTM_MAX_BO_PRIORITY;
 	     ++cursor->priority)
-		list_for_each_entry(res, &man->lru[cursor->priority], lru)
-			return res;
+		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
+			if (ttm_lru_item_is_res(lru))
+				ttm_lru_item_to_res(lru);
+		}
 
 	return NULL;
 }
diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
index 69769355139f..4babc4ff10b0 100644
--- a/include/drm/ttm/ttm_resource.h
+++ b/include/drm/ttm/ttm_resource.h
@@ -49,6 +49,43 @@ struct io_mapping;
 struct sg_table;
 struct scatterlist;
 
+/**
+ * enum ttm_lru_item_type - enumerate ttm_lru_item subclasses
+ */
+enum ttm_lru_item_type {
+	/** @TTM_LRU_RESOURCE: The resource subclass */
+	TTM_LRU_RESOURCE,
+	/** @TTM_LRU_HITCH: The iterator hitch subclass */
+	TTM_LRU_HITCH
+};
+
+/**
+ * struct ttm_lru_item - The TTM lru list node base class
+ * @link: The list link
+ * @type: The subclass type
+ */
+struct ttm_lru_item {
+	struct list_head link;
+	enum ttm_lru_item_type type;
+};
+
+/**
+ * ttm_lru_item_init() - initialize a struct ttm_lru_item
+ * @item: The item to initialize
+ * @type: The subclass type
+ */
+static inline void ttm_lru_item_init(struct ttm_lru_item *item,
+				     enum ttm_lru_item_type type)
+{
+	item->type = type;
+	INIT_LIST_HEAD(&item->link);
+}
+
+static inline bool ttm_lru_item_is_res(const struct ttm_lru_item *item)
+{
+	return item->type == TTM_LRU_RESOURCE;
+}
+
 struct ttm_resource_manager_func {
 	/**
 	 * struct ttm_resource_manager_func member alloc
@@ -217,9 +254,21 @@ struct ttm_resource {
 	/**
 	 * @lru: Least recently used list, see &ttm_resource_manager.lru
 	 */
-	struct list_head lru;
+	struct ttm_lru_item lru;
 };
 
+/**
+ * ttm_lru_item_to_res() - Downcast a struct ttm_lru_item to a struct ttm_resource
+ * @item: The struct ttm_lru_item to downcast
+ *
+ * Return: Pointer to the embedding struct ttm_resource
+ */
+static inline struct ttm_resource *
+ttm_lru_item_to_res(struct ttm_lru_item *item)
+{
+	return container_of(item, struct ttm_resource, lru);
+}
+
 /**
  * struct ttm_resource_cursor
  *
-- 
2.44.0

[PATCH 2/8] drm/ttm: Use LRU hitches

[Thomas Hellström]

Have iterators insert themselves into the list they are iterating
over using hitch list nodes. Since only the iterator owner
can remove these list nodes from the list, it's safe to unlock
the list and when continuing, use them as a starting point. Due to
the way LRU bumping works in TTM, newly added items will not be
missed, and bumped items will be iterated over a second time before
reaching the end of the list.

The exception is list with bulk move sublists. When bumping a
sublist, a hitch that is part of that sublist will also be moved
and we might miss items if restarting from it. This will be
addressed in a later patch.

v2:
- Updated ttm_resource_cursor_fini() documentation.

Cc: Christian König <christian.koenig@amd.com>
Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
Cc: <dri-devel@lists.freedesktop.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/ttm/ttm_bo.c       |  1 +
 drivers/gpu/drm/ttm/ttm_device.c   |  9 ++-
 drivers/gpu/drm/ttm/ttm_resource.c | 94 ++++++++++++++++++++----------
 include/drm/ttm/ttm_resource.h     | 16 +++--
 4 files changed, 82 insertions(+), 38 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index e059b1e1b13b..b6f75a0ff2e5 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -622,6 +622,7 @@ int ttm_mem_evict_first(struct ttm_device *bdev,
 		if (locked)
 			dma_resv_unlock(res->bo->base.resv);
 	}
+	ttm_resource_cursor_fini_locked(&cursor);
 
 	if (!bo) {
 		if (busy_bo && !ttm_bo_get_unless_zero(busy_bo))
diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index f27406e851e5..e8a6a1dab669 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -169,12 +169,17 @@ int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
 			num_pages = PFN_UP(bo->base.size);
 			ret = ttm_bo_swapout(bo, ctx, gfp_flags);
 			/* ttm_bo_swapout has dropped the lru_lock */
-			if (!ret)
+			if (!ret) {
+				ttm_resource_cursor_fini(&cursor);
 				return num_pages;
-			if (ret != -EBUSY)
+			}
+			if (ret != -EBUSY) {
+				ttm_resource_cursor_fini(&cursor);
 				return ret;
+			}
 		}
 	}
+	ttm_resource_cursor_fini_locked(&cursor);
 	spin_unlock(&bdev->lru_lock);
 	return 0;
 }
diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
index 7aa5ca5c0e33..ccc31ad85e3b 100644
--- a/drivers/gpu/drm/ttm/ttm_resource.c
+++ b/drivers/gpu/drm/ttm/ttm_resource.c
@@ -32,6 +32,37 @@
 
 #include <drm/drm_util.h>
 
+/**
+ * ttm_resource_cursor_fini_locked() - Finalize the LRU list cursor usage
+ * @cursor: The struct ttm_resource_cursor to finalize.
+ *
+ * The function pulls the LRU list cursor off any lists it was previusly
+ * attached to. Needs to be called with the LRU lock held. The function
+ * can be called multiple times after eachother.
+ */
+void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor)
+{
+	lockdep_assert_held(&cursor->man->bdev->lru_lock);
+	list_del_init(&cursor->hitch.link);
+}
+
+/**
+ * ttm_resource_cursor_fini() - Finalize the LRU list cursor usage
+ * @cursor: The struct ttm_resource_cursor to finalize.
+ *
+ * The function pulls the LRU list cursor off any lists it was previusly
+ * attached to. Needs to be called without the LRU list lock held. The
+ * function can be called multiple times after eachother.
+ */
+void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor)
+{
+	spinlock_t *lru_lock = &cursor->man->bdev->lru_lock;
+
+	spin_lock(lru_lock);
+	ttm_resource_cursor_fini_locked(cursor);
+	spin_unlock(lru_lock);
+}
+
 /**
  * ttm_lru_bulk_move_init - initialize a bulk move structure
  * @bulk: the structure to init
@@ -484,62 +515,63 @@ void ttm_resource_manager_debug(struct ttm_resource_manager *man,
 EXPORT_SYMBOL(ttm_resource_manager_debug);
 
 /**
- * ttm_resource_manager_first
- *
- * @man: resource manager to iterate over
+ * ttm_resource_manager_next() - Continue iterating over the resource manager
+ * resources
  * @cursor: cursor to record the position
  *
- * Returns the first resource from the resource manager.
+ * Return: The next resource from the resource manager.
  */
 struct ttm_resource *
-ttm_resource_manager_first(struct ttm_resource_manager *man,
-			   struct ttm_resource_cursor *cursor)
+ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
 {
+	struct ttm_resource_manager *man = cursor->man;
 	struct ttm_lru_item *lru;
 
 	lockdep_assert_held(&man->bdev->lru_lock);
 
-	for (cursor->priority = 0; cursor->priority < TTM_MAX_BO_PRIORITY;
-	     ++cursor->priority)
-		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
-			if (ttm_lru_item_is_res(lru))
+	do {
+		lru = &cursor->hitch;
+		list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
+			if (ttm_lru_item_is_res(lru)) {
+				list_move(&cursor->hitch.link, &lru->link);
 				return ttm_lru_item_to_res(lru);
+			}
 		}
 
+		if (++cursor->priority >= TTM_MAX_BO_PRIORITY)
+			break;
+
+		list_move(&cursor->hitch.link, &man->lru[cursor->priority]);
+	} while (true);
+
+	list_del_init(&cursor->hitch.link);
+
 	return NULL;
 }
 
 /**
- * ttm_resource_manager_next
- *
+ * ttm_resource_manager_first() - Start iterating over the resources
+ * of a resource manager
  * @man: resource manager to iterate over
  * @cursor: cursor to record the position
- * @res: the current resource pointer
  *
- * Returns the next resource from the resource manager.
+ * Initializes the cursor and starts iterating. When done iterating,
+ * the caller must explicitly call ttm_resource_cursor_fini().
+ *
+ * Return: The first resource from the resource manager.
  */
 struct ttm_resource *
-ttm_resource_manager_next(struct ttm_resource_manager *man,
-			  struct ttm_resource_cursor *cursor,
-			  struct ttm_resource *res)
+ttm_resource_manager_first(struct ttm_resource_manager *man,
+			   struct ttm_resource_cursor *cursor)
 {
-	struct ttm_lru_item *lru = &res->lru;
-
 	lockdep_assert_held(&man->bdev->lru_lock);
 
-	list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
-		if (ttm_lru_item_is_res(lru))
-			return ttm_lru_item_to_res(lru);
-	}
+	cursor->priority = 0;
+	cursor->man = man;
+	ttm_lru_item_init(&cursor->hitch, TTM_LRU_HITCH);
+	list_move(&cursor->hitch.link, &man->lru[cursor->priority]);
 
-	for (++cursor->priority; cursor->priority < TTM_MAX_BO_PRIORITY;
-	     ++cursor->priority)
-		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
-			if (ttm_lru_item_is_res(lru))
-				ttm_lru_item_to_res(lru);
-		}
-
-	return NULL;
+	return ttm_resource_manager_next(cursor);
 }
 
 static void ttm_kmap_iter_iomap_map_local(struct ttm_kmap_iter *iter,
diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
index 4babc4ff10b0..dfc01258c981 100644
--- a/include/drm/ttm/ttm_resource.h
+++ b/include/drm/ttm/ttm_resource.h
@@ -271,15 +271,23 @@ ttm_lru_item_to_res(struct ttm_lru_item *item)
 
 /**
  * struct ttm_resource_cursor
- *
+ * @man: The resource manager currently being iterated over
+ * @hitch: A hitch list node inserted before the next resource
+ * to iterate over.
  * @priority: the current priority
  *
  * Cursor to iterate over the resources in a manager.
  */
 struct ttm_resource_cursor {
+	struct ttm_resource_manager *man;
+	struct ttm_lru_item hitch;
 	unsigned int priority;
 };
 
+void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor);
+
+void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor);
+
 /**
  * struct ttm_lru_bulk_move_pos
  *
@@ -438,9 +446,7 @@ struct ttm_resource *
 ttm_resource_manager_first(struct ttm_resource_manager *man,
 			   struct ttm_resource_cursor *cursor);
 struct ttm_resource *
-ttm_resource_manager_next(struct ttm_resource_manager *man,
-			  struct ttm_resource_cursor *cursor,
-			  struct ttm_resource *res);
+ttm_resource_manager_next(struct ttm_resource_cursor *cursor);
 
 /**
  * ttm_resource_manager_for_each_res - iterate over all resources
@@ -452,7 +458,7 @@ ttm_resource_manager_next(struct ttm_resource_manager *man,
  */
 #define ttm_resource_manager_for_each_res(man, cursor, res)		\
 	for (res = ttm_resource_manager_first(man, cursor); res;	\
-	     res = ttm_resource_manager_next(man, cursor, res))
+	     res = ttm_resource_manager_next(cursor))
 
 struct ttm_kmap_iter *
 ttm_kmap_iter_iomap_init(struct ttm_kmap_iter_iomap *iter_io,
-- 
2.44.0

[PATCH 3/8] drm/ttm, drm/amdgpu, drm/xe: Consider hitch moves within bulk sublist moves

[Thomas Hellström]

To address the problem with hitches moving when bulk move
sublists are lru-bumped, register the list cursors with the
ttm_lru_bulk_move structure when traversing its list, and
when lru-bumping the list, move the cursor hitch to the tail.
This also means it's mandatory for drivers to call
ttm_lru_bulk_move_init() and ttm_lru_bulk_move_fini() when
initializing and finalizing the bulk move structure, so add
those calls to the amdgpu- and xe driver.

Compared to v1 this is slightly more code but less fragile
and hopefully easier to understand.

v2:
- Completely rework the functionality
v3:
- Avoid a NULL pointer dereference assigning manager->mem_type
v4:
- Remove some leftover code causing build problems

Cc: Christian König <christian.koenig@amd.com>
Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
Cc: <dri-devel@lists.freedesktop.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c |  4 ++
 drivers/gpu/drm/ttm/ttm_resource.c     | 90 +++++++++++++++++++++++++-
 drivers/gpu/drm/xe/xe_vm.c             |  4 ++
 include/drm/ttm/ttm_device.h           |  2 +
 include/drm/ttm/ttm_resource.h         | 55 ++++++++++------
 5 files changed, 134 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index 4299ce386322..18bf174c8d47 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -2368,6 +2368,8 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm,
 	if (r)
 		return r;
 
+	ttm_lru_bulk_move_init(&vm->lru_bulk_move);
+
 	vm->is_compute_context = false;
 
 	vm->use_cpu_for_update = !!(adev->vm_manager.vm_update_mode &
@@ -2431,6 +2433,7 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm,
 error_free_delayed:
 	dma_fence_put(vm->last_tlb_flush);
 	dma_fence_put(vm->last_unlocked);
+	ttm_lru_bulk_move_fini(&adev->mman.bdev, &vm->lru_bulk_move);
 	amdgpu_vm_fini_entities(vm);
 
 	return r;
@@ -2587,6 +2590,7 @@ void amdgpu_vm_fini(struct amdgpu_device *adev, struct amdgpu_vm *vm)
 		}
 	}
 
+	ttm_lru_bulk_move_fini(&adev->mman.bdev, &vm->lru_bulk_move);
 }
 
 /**
diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
index ccc31ad85e3b..89f19fb6e2b3 100644
--- a/drivers/gpu/drm/ttm/ttm_resource.c
+++ b/drivers/gpu/drm/ttm/ttm_resource.c
@@ -32,6 +32,49 @@
 
 #include <drm/drm_util.h>
 
+/* Detach the cursor from the bulk move list*/
+static void
+ttm_resource_cursor_clear_bulk(struct ttm_resource_cursor *cursor)
+{
+	cursor->bulk = NULL;
+	list_del_init(&cursor->bulk_link);
+}
+
+/* Move the cursor to the end of the bulk move list it's in */
+static void ttm_resource_cursor_move_bulk_tail(struct ttm_lru_bulk_move *bulk,
+					       struct ttm_resource_cursor *cursor)
+{
+	struct ttm_lru_bulk_move_pos *pos;
+
+	if (WARN_ON_ONCE(bulk != cursor->bulk)) {
+		list_del_init(&cursor->bulk_link);
+		return;
+	}
+
+	pos = &bulk->pos[cursor->man->mem_type][cursor->priority];
+	if (pos)
+		list_move(&cursor->hitch.link, &pos->last->lru.link);
+	ttm_resource_cursor_clear_bulk(cursor);
+}
+
+/* Move all cursors attached to a bulk move to its end */
+static void ttm_bulk_move_adjust_cursors(struct ttm_lru_bulk_move *bulk)
+{
+	struct ttm_resource_cursor *cursor, *next;
+
+	list_for_each_entry_safe(cursor, next, &bulk->cursor_list, bulk_link)
+		ttm_resource_cursor_move_bulk_tail(bulk, cursor);
+}
+
+/* Remove a cursor from an empty bulk move list */
+static void ttm_bulk_move_drop_cursors(struct ttm_lru_bulk_move *bulk)
+{
+	struct ttm_resource_cursor *cursor, *next;
+
+	list_for_each_entry_safe(cursor, next, &bulk->cursor_list, bulk_link)
+		ttm_resource_cursor_clear_bulk(cursor);
+}
+
 /**
  * ttm_resource_cursor_fini_locked() - Finalize the LRU list cursor usage
  * @cursor: The struct ttm_resource_cursor to finalize.
@@ -44,6 +87,7 @@ void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor)
 {
 	lockdep_assert_held(&cursor->man->bdev->lru_lock);
 	list_del_init(&cursor->hitch.link);
+	ttm_resource_cursor_clear_bulk(cursor);
 }
 
 /**
@@ -72,9 +116,27 @@ void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor)
 void ttm_lru_bulk_move_init(struct ttm_lru_bulk_move *bulk)
 {
 	memset(bulk, 0, sizeof(*bulk));
+	INIT_LIST_HEAD(&bulk->cursor_list);
 }
 EXPORT_SYMBOL(ttm_lru_bulk_move_init);
 
+/**
+ * ttm_lru_bulk_move_fini - finalize a bulk move structure
+ * @bdev: The struct ttm_device
+ * @bulk: the structure to finalize
+ *
+ * Sanity checks that bulk moves don't have any
+ * resources left and hence no cursors attached.
+ */
+void ttm_lru_bulk_move_fini(struct ttm_device *bdev,
+			    struct ttm_lru_bulk_move *bulk)
+{
+	spin_lock(&bdev->lru_lock);
+	ttm_bulk_move_drop_cursors(bulk);
+	spin_unlock(&bdev->lru_lock);
+}
+EXPORT_SYMBOL(ttm_lru_bulk_move_fini);
+
 /**
  * ttm_lru_bulk_move_tail - bulk move range of resources to the LRU tail.
  *
@@ -87,6 +149,7 @@ void ttm_lru_bulk_move_tail(struct ttm_lru_bulk_move *bulk)
 {
 	unsigned i, j;
 
+	ttm_bulk_move_adjust_cursors(bulk);
 	for (i = 0; i < TTM_NUM_MEM_TYPES; ++i) {
 		for (j = 0; j < TTM_MAX_BO_PRIORITY; ++j) {
 			struct ttm_lru_bulk_move_pos *pos = &bulk->pos[i][j];
@@ -418,6 +481,7 @@ void ttm_resource_manager_init(struct ttm_resource_manager *man,
 	man->bdev = bdev;
 	man->size = size;
 	man->usage = 0;
+	man->mem_type = TTM_NUM_MEM_TYPES;
 
 	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i)
 		INIT_LIST_HEAD(&man->lru[i]);
@@ -514,6 +578,27 @@ void ttm_resource_manager_debug(struct ttm_resource_manager *man,
 }
 EXPORT_SYMBOL(ttm_resource_manager_debug);
 
+static void
+ttm_resource_cursor_check_bulk(struct ttm_resource_cursor *cursor,
+			       struct ttm_lru_item *next_lru)
+{
+	struct ttm_resource *next = ttm_lru_item_to_res(next_lru);
+	struct ttm_lru_bulk_move *bulk = NULL;
+	struct ttm_buffer_object *bo = next->bo;
+
+	lockdep_assert_held(&cursor->man->bdev->lru_lock);
+	if (bo && bo->resource == next)
+		bulk = bo->bulk_move;
+
+	if (cursor->bulk != bulk) {
+		if (bulk)
+			list_move_tail(&cursor->bulk_link, &bulk->cursor_list);
+		else
+			list_del_init(&cursor->bulk_link);
+		cursor->bulk = bulk;
+	}
+}
+
 /**
  * ttm_resource_manager_next() - Continue iterating over the resource manager
  * resources
@@ -533,6 +618,7 @@ ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
 		lru = &cursor->hitch;
 		list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
 			if (ttm_lru_item_is_res(lru)) {
+				ttm_resource_cursor_check_bulk(cursor, lru);
 				list_move(&cursor->hitch.link, &lru->link);
 				return ttm_lru_item_to_res(lru);
 			}
@@ -542,9 +628,10 @@ ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
 			break;
 
 		list_move(&cursor->hitch.link, &man->lru[cursor->priority]);
+		ttm_resource_cursor_clear_bulk(cursor);
 	} while (true);
 
-	list_del_init(&cursor->hitch.link);
+	ttm_resource_cursor_fini_locked(cursor);
 
 	return NULL;
 }
@@ -569,6 +656,7 @@ ttm_resource_manager_first(struct ttm_resource_manager *man,
 	cursor->priority = 0;
 	cursor->man = man;
 	ttm_lru_item_init(&cursor->hitch, TTM_LRU_HITCH);
+	INIT_LIST_HEAD(&cursor->bulk_link);
 	list_move(&cursor->hitch.link, &man->lru[cursor->priority]);
 
 	return ttm_resource_manager_next(cursor);
diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index 8b32aa5003df..542e57e1ad07 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -1361,6 +1361,8 @@ struct xe_vm *xe_vm_create(struct xe_device *xe, u32 flags)
 
 	INIT_WORK(&vm->destroy_work, vm_destroy_work_func);
 
+	ttm_lru_bulk_move_init(&vm->lru_bulk_move);
+
 	INIT_LIST_HEAD(&vm->preempt.exec_queues);
 	vm->preempt.min_run_period_ms = 10;	/* FIXME: Wire up to uAPI */
 
@@ -1478,6 +1480,7 @@ struct xe_vm *xe_vm_create(struct xe_device *xe, u32 flags)
 	mutex_destroy(&vm->snap_mutex);
 	for_each_tile(tile, xe, id)
 		xe_range_fence_tree_fini(&vm->rftree[id]);
+	ttm_lru_bulk_move_fini(&xe->ttm, &vm->lru_bulk_move);
 	kfree(vm);
 	if (!(flags & XE_VM_FLAG_MIGRATION))
 		xe_device_mem_access_put(xe);
@@ -1617,6 +1620,7 @@ static void vm_destroy_work_func(struct work_struct *w)
 		XE_WARN_ON(vm->pt_root[id]);
 
 	trace_xe_vm_free(vm);
+	ttm_lru_bulk_move_fini(&xe->ttm, &vm->lru_bulk_move);
 	kfree(vm);
 }
 
diff --git a/include/drm/ttm/ttm_device.h b/include/drm/ttm/ttm_device.h
index c22f30535c84..8816d5ba8cb3 100644
--- a/include/drm/ttm/ttm_device.h
+++ b/include/drm/ttm/ttm_device.h
@@ -285,6 +285,8 @@ static inline void ttm_set_driver_manager(struct ttm_device *bdev, int type,
 {
 	BUILD_BUG_ON(__builtin_constant_p(type) && type >= TTM_NUM_MEM_TYPES);
 	bdev->man_drv[type] = manager;
+	if (manager)
+		manager->mem_type = type;
 }
 
 int ttm_device_init(struct ttm_device *bdev, const struct ttm_device_funcs *funcs,
diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
index dfc01258c981..6b7bf4c18997 100644
--- a/include/drm/ttm/ttm_resource.h
+++ b/include/drm/ttm/ttm_resource.h
@@ -211,6 +211,9 @@ struct ttm_resource_manager {
 	 * bdev->lru_lock.
 	 */
 	uint64_t usage;
+
+	/** @mem_type: The memory type used for this manager. */
+	unsigned int mem_type;
 };
 
 /**
@@ -269,25 +272,6 @@ ttm_lru_item_to_res(struct ttm_lru_item *item)
 	return container_of(item, struct ttm_resource, lru);
 }
 
-/**
- * struct ttm_resource_cursor
- * @man: The resource manager currently being iterated over
- * @hitch: A hitch list node inserted before the next resource
- * to iterate over.
- * @priority: the current priority
- *
- * Cursor to iterate over the resources in a manager.
- */
-struct ttm_resource_cursor {
-	struct ttm_resource_manager *man;
-	struct ttm_lru_item hitch;
-	unsigned int priority;
-};
-
-void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor);
-
-void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor);
-
 /**
  * struct ttm_lru_bulk_move_pos
  *
@@ -303,8 +287,9 @@ struct ttm_lru_bulk_move_pos {
 
 /**
  * struct ttm_lru_bulk_move
- *
  * @pos: first/last lru entry for resources in the each domain/priority
+ * @cursor_list: The list of cursors currently traversing any of
+ * the sublists of @pos. Protected by the ttm device's lru_lock.
  *
  * Container for the current bulk move state. Should be used with
  * ttm_lru_bulk_move_init() and ttm_bo_set_bulk_move().
@@ -314,8 +299,36 @@ struct ttm_lru_bulk_move_pos {
  */
 struct ttm_lru_bulk_move {
 	struct ttm_lru_bulk_move_pos pos[TTM_NUM_MEM_TYPES][TTM_MAX_BO_PRIORITY];
+	struct list_head cursor_list;
+};
+
+/**
+ * struct ttm_resource_cursor
+ * @man: The resource manager currently being iterated over
+ * @hitch: A hitch list node inserted before the next resource
+ * to iterate over.
+ * @bulk_link: A list link for the list of cursors traversing the
+ * bulk sublist of @bulk. Protected by the ttm device's lru_lock.
+ * @bulk: Pointer to struct ttm_lru_bulk_move whose subrange @hitch is
+ * inserted to. NULL if none. Never dereference this pointer since
+ * the struct ttm_lru_bulk_move object pointed to might have been
+ * freed. The pointer is only for comparison.
+ * @priority: the current priority
+ *
+ * Cursor to iterate over the resources in a manager.
+ */
+struct ttm_resource_cursor {
+	struct ttm_resource_manager *man;
+	struct ttm_lru_item hitch;
+	struct list_head bulk_link;
+	struct ttm_lru_bulk_move *bulk;
+	unsigned int priority;
 };
 
+void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor);
+
+void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor);
+
 /**
  * struct ttm_kmap_iter_iomap - Specialization for a struct io_mapping +
  * struct sg_table backed struct ttm_resource.
@@ -404,6 +417,8 @@ ttm_resource_manager_cleanup(struct ttm_resource_manager *man)
 
 void ttm_lru_bulk_move_init(struct ttm_lru_bulk_move *bulk);
 void ttm_lru_bulk_move_tail(struct ttm_lru_bulk_move *bulk);
+void ttm_lru_bulk_move_fini(struct ttm_device *bdev,
+			    struct ttm_lru_bulk_move *bulk);
 
 void ttm_resource_add_bulk_move(struct ttm_resource *res,
 				struct ttm_buffer_object *bo);
-- 
2.44.0

[PATCH 4/8] drm/ttm: Allow continued swapout after -ENOSPC falure

[Thomas Hellström]

The -ENOSPC failure from ttm_bo_swapout() meant that the lru_lock
was dropped and simply restarting the iteration meant we'd likely
hit the same error again on the same resource. Now that we can
restart the iteration even if the lock was dropped, do that.

Cc: Christian König <christian.koenig@amd.com>
Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
Cc: <dri-devel@lists.freedesktop.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/ttm/ttm_device.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index e8a6a1dab669..4a030b4bc848 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -168,15 +168,20 @@ int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
 
 			num_pages = PFN_UP(bo->base.size);
 			ret = ttm_bo_swapout(bo, ctx, gfp_flags);
-			/* ttm_bo_swapout has dropped the lru_lock */
-			if (!ret) {
-				ttm_resource_cursor_fini(&cursor);
-				return num_pages;
-			}
-			if (ret != -EBUSY) {
-				ttm_resource_cursor_fini(&cursor);
-				return ret;
+			/* Couldn't swap out, and retained the lru_lock */
+			if (ret == -EBUSY)
+				continue;
+			/* Couldn't swap out and dropped the lru_lock */
+			if (ret == -ENOSPC) {
+				spin_lock(&bdev->lru_lock);
+				continue;
 			}
+			/*
+			 * Dropped the lock and either succeeded or
+			 * hit an error that forces us to break.
+			 */
+			ttm_resource_cursor_fini(&cursor);
+			return ret ? ret : num_pages;
 		}
 	}
 	ttm_resource_cursor_fini_locked(&cursor);
-- 
2.44.0

[RFC PATCH 5/8] drm/ttm: Add a virtual base class for graphics memory backup

[Thomas Hellström]

Initially intended for experimenting with different backup
solutions (shmem vs direct swap cache insertion), abstract
the backup destination using a virtual base class.

Also provide a sample implementation for shmem.

While when settling on a preferred backup solution, one could
perhaps skip the abstraction, this functionality may actually
come in handy for configurable dedicated graphics memory
backup to fast nvme files or similar, whithout affecting
swap-space. Could indeed be useful for VRAM backup on S4 and
other cases.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/ttm/Makefile           |   2 +-
 drivers/gpu/drm/ttm/ttm_backup_shmem.c | 137 +++++++++++++++++++++++++
 include/drm/ttm/ttm_backup.h           | 136 ++++++++++++++++++++++++
 3 files changed, 274 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/ttm/ttm_backup_shmem.c
 create mode 100644 include/drm/ttm/ttm_backup.h

diff --git a/drivers/gpu/drm/ttm/Makefile b/drivers/gpu/drm/ttm/Makefile
index dad298127226..5e980dd90e41 100644
--- a/drivers/gpu/drm/ttm/Makefile
+++ b/drivers/gpu/drm/ttm/Makefile
@@ -4,7 +4,7 @@
 
 ttm-y := ttm_tt.o ttm_bo.o ttm_bo_util.o ttm_bo_vm.o ttm_module.o \
 	ttm_execbuf_util.o ttm_range_manager.o ttm_resource.o ttm_pool.o \
-	ttm_device.o ttm_sys_manager.o
+	ttm_device.o ttm_sys_manager.o ttm_backup_shmem.o
 ttm-$(CONFIG_AGP) += ttm_agp_backend.o
 
 obj-$(CONFIG_DRM_TTM) += ttm.o
diff --git a/drivers/gpu/drm/ttm/ttm_backup_shmem.c b/drivers/gpu/drm/ttm/ttm_backup_shmem.c
new file mode 100644
index 000000000000..79c2f552863a
--- /dev/null
+++ b/drivers/gpu/drm/ttm/ttm_backup_shmem.c
@@ -0,0 +1,137 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#include <drm/ttm/ttm_backup.h>
+#include <linux/page-flags.h>
+
+/**
+ * struct ttm_backup_shmem - A shmem based ttm_backup subclass.
+ * @backup: The base struct ttm_backup
+ * @filp: The associated shmem object
+ */
+struct ttm_backup_shmem {
+	struct ttm_backup backup;
+	struct file *filp;
+};
+
+static struct ttm_backup_shmem *to_backup_shmem(struct ttm_backup *backup)
+{
+	return container_of(backup, struct ttm_backup_shmem, backup);
+}
+
+static void ttm_backup_shmem_drop(struct ttm_backup *backup, unsigned long handle)
+{
+	handle -= 1;
+	shmem_truncate_range(file_inode(to_backup_shmem(backup)->filp), handle,
+			     handle + 1);
+}
+
+static int ttm_backup_shmem_copy_page(struct ttm_backup *backup, struct page *dst,
+				      unsigned long handle, bool killable)
+{
+	struct file *filp = to_backup_shmem(backup)->filp;
+	struct address_space *mapping = filp->f_mapping;
+	struct folio *from_folio;
+
+	handle -= 1;
+	from_folio = shmem_read_folio(mapping, handle);
+	if (IS_ERR(from_folio))
+		return PTR_ERR(from_folio);
+
+	/* Note: Use drm_memcpy_from_wc? */
+	copy_highpage(dst, folio_file_page(from_folio, handle));
+	folio_put(from_folio);
+
+	return 0;
+}
+
+static unsigned long
+ttm_backup_shmem_backup_page(struct ttm_backup *backup, struct page *page,
+			     bool writeback, pgoff_t i, gfp_t page_gfp,
+			     gfp_t alloc_gfp)
+{
+	struct file *filp = to_backup_shmem(backup)->filp;
+	struct address_space *mapping = filp->f_mapping;
+	unsigned long handle = 0;
+	struct folio *to_folio;
+	int ret;
+
+	to_folio = shmem_read_folio_gfp(mapping, i, alloc_gfp);
+	if (IS_ERR(to_folio))
+		return handle;
+
+	folio_mark_accessed(to_folio);
+	folio_lock(to_folio);
+	folio_mark_dirty(to_folio);
+	copy_highpage(folio_file_page(to_folio, i), page);
+	handle = i + 1;
+
+	if (writeback && !folio_mapped(to_folio) && folio_clear_dirty_for_io(to_folio)) {
+		struct writeback_control wbc = {
+			.sync_mode = WB_SYNC_NONE,
+			.nr_to_write = SWAP_CLUSTER_MAX,
+			.range_start = 0,
+			.range_end = LLONG_MAX,
+			.for_reclaim = 1,
+		};
+		folio_set_reclaim(to_folio);
+		ret = mapping->a_ops->writepage(folio_page(to_folio, 0), &wbc);
+		if (!folio_test_writeback(to_folio))
+			folio_clear_reclaim(to_folio);
+		/* If writepage succeeds, it unlocks the folio */
+		if (ret)
+			folio_unlock(to_folio);
+	} else {
+		folio_unlock(to_folio);
+	}
+
+	folio_put(to_folio);
+
+	return handle;
+}
+
+static void ttm_backup_shmem_fini(struct ttm_backup *backup)
+{
+	struct ttm_backup_shmem *sbackup = to_backup_shmem(backup);
+
+	fput(sbackup->filp);
+	kfree(sbackup);
+}
+
+static const struct ttm_backup_ops ttm_backup_shmem_ops = {
+	.drop = ttm_backup_shmem_drop,
+	.copy_backed_up_page = ttm_backup_shmem_copy_page,
+	.backup_page = ttm_backup_shmem_backup_page,
+	.fini = ttm_backup_shmem_fini,
+};
+
+/**
+ * ttm_backup_shmem_create() - Create a shmem-based struct backup.
+ * @size: The maximum size (in bytes) to back up.
+ *
+ * Create a backup utilizing shmem objects.
+ *
+ * Return: A pointer to a struct ttm_backup on success,
+ * an error pointer on error.
+ */
+struct ttm_backup *ttm_backup_shmem_create(loff_t size)
+{
+	struct ttm_backup_shmem *sbackup =
+		kzalloc(sizeof(*sbackup), GFP_KERNEL | __GFP_ACCOUNT);
+
+	if (!sbackup)
+		return ERR_PTR(-ENOMEM);
+
+	sbackup->filp = shmem_file_setup("ttm shmem backup", size, 0);
+	if (IS_ERR(sbackup->filp)) {
+		kfree(sbackup);
+		return ERR_CAST(sbackup->filp);
+	}
+
+	sbackup->backup.ops = &ttm_backup_shmem_ops;
+
+	return &sbackup->backup;
+}
+EXPORT_SYMBOL_GPL(ttm_backup_shmem_create);
diff --git a/include/drm/ttm/ttm_backup.h b/include/drm/ttm/ttm_backup.h
new file mode 100644
index 000000000000..88e8b97a6fdc
--- /dev/null
+++ b/include/drm/ttm/ttm_backup.h
@@ -0,0 +1,136 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#ifndef _TTM_BACKUP_H_
+#define _TTM_BACKUP_H_
+
+#include <linux/mm_types.h>
+#include <linux/shmem_fs.h>
+
+struct ttm_backup;
+
+/**
+ * ttm_backup_handle_to_page_ptr() - Convert handle to struct page pointer
+ * @handle: The handle to convert.
+ *
+ * Converts an opaque handle received from the
+ * struct ttm_backoup_ops::backup_page() function to an (invalid)
+ * struct page pointer suitable for a struct page array.
+ *
+ * Return: An (invalid) struct page pointer.
+ */
+static inline struct page *
+ttm_backup_handle_to_page_ptr(unsigned long handle)
+{
+	return (struct page *)(handle << 1 | 1);
+}
+
+/**
+ * ttm_backup_page_ptr_is_handle() - Whether a struct page pointer is a handle
+ * @page: The struct page pointer to check.
+ *
+ * Return: true if the struct page pointer is a handld returned from
+ * ttm_backup_handle_to_page_ptr(). False otherwise.
+ */
+static inline bool ttm_backup_page_ptr_is_handle(const struct page *page)
+{
+	return (unsigned long)page & 1;
+}
+
+/**
+ * ttm_backup_page_ptr_to_handle() - Convert a struct page pointer to a handle
+ * @page: The struct page pointer to convert
+ *
+ * Return: The handle that was previously used in
+ * ttm_backup_handle_to_page_ptr() to obtain a struct page pointer, suitable
+ * for use as argument in the struct ttm_backup_ops drop() or
+ * copy_backed_up_page() functions.
+ */
+static inline unsigned long
+ttm_backup_page_ptr_to_handle(const struct page *page)
+{
+	WARN_ON(!ttm_backup_page_ptr_is_handle(page));
+	return (unsigned long)page >> 1;
+}
+
+/** struct ttm_backup_ops - A struct ttm_backup backend operations */
+struct ttm_backup_ops {
+	/**
+	 * drop - release memory associated with a handle
+	 * @backup: The struct backup pointer used to obtain the handle
+	 * @handle: The handle obtained from the @backup_page function.
+	 */
+	void (*drop)(struct ttm_backup *backup, unsigned long handle);
+
+	/**
+	 * copy_backed_up_page - Copy the contents of a previously backed
+	 * up page
+	 * @backup: The struct backup pointer used to back up the page.
+	 * @dst: The struct page to copy into.
+	 * @handle: The handle returned when the page was backed up.
+	 * @intr: Try to perform waits interruptable or at least killable.
+	 *
+	 * Return: 0 on success, Negative error code on failure, notably
+	 * -EINTR if @intr was set to true and a signal is pending.
+	 */
+	int (*copy_backed_up_page)(struct ttm_backup *backup, struct page *dst,
+				   unsigned long handle, bool intr);
+
+	/**
+	 * backup_page - Backup a page
+	 * @backup: The struct backup pointer to use.
+	 * @page: The page to back up.
+	 * @writeback: Whether to perform immediate writeback of the page.
+	 * This may have performance implications.
+	 * @i: A unique integer for each page and each struct backup.
+	 * This is a hint allowing the backup backend to avoid managing
+	 * its address space separately.
+	 * @page_gfp: The gfp value used when the page was allocated.
+	 * This is used for accounting purposes.
+	 * @alloc_gfp: The gpf to be used when the backend needs to allocaete
+	 * memory.
+	 *
+	 * Return: A handle on success. 0 on failure.
+	 * (This is following the swp_entry_t convention).
+	 *
+	 * Note: This function could be extended to back up a folio and
+	 * backends would then split the folio internally if needed.
+	 * Drawback is that the caller would then have to keep track of
+	 */
+	unsigned long (*backup_page)(struct ttm_backup *backup, struct page *page,
+				     bool writeback, pgoff_t i, gfp_t page_gfp,
+				     gfp_t alloc_gfp);
+	/**
+	 * fini - Free the struct backup resources after last use.
+	 * @backup: Pointer to the struct backup whose resources to free.
+	 *
+	 * After a call to @fini, it's illegal to use the @backup pointer.
+	 */
+	void (*fini)(struct ttm_backup *backup);
+};
+
+/**
+ * struct ttm_backup - Abstract a backup backend.
+ * @ops: The operations as described above.
+ *
+ * The struct ttm_backup is intended to be subclassed by the
+ * backend implementation.
+ */
+struct ttm_backup {
+	const struct ttm_backup_ops *ops;
+};
+
+/**
+ * ttm_backup_shmem_create() - Create a shmem-based struct backup.
+ * @size: The maximum size (in bytes) to back up.
+ *
+ * Create a backup utilizing shmem objects.
+ *
+ * Return: A pointer to a struct ttm_backup on success,
+ * an error pointer on error.
+ */
+struct ttm_backup *ttm_backup_shmem_create(loff_t size);
+
+#endif
-- 
2.44.0

[RFC PATCH 6/8] drm/ttm/pool: Provide a helper to shrink pages.

[Thomas Hellström]

Provide a helper to shrink ttm_tt page-vectors on a per-page
basis. A ttm_backup backend could then in theory get away with
allocating a single temporary page for each struct ttm_tt.

This is accomplished by splitting larger pages before trying to
back them up.

In the future we could allow ttm_backup to handle backing up
large pages as well, but currently there's no benefit in
doing that, since the shmem backup backend would have to
split those anyway to avoid allocating too much temporary
memory, and if the backend instead inserts pages into the
swap-cache, those are split on reclaim by the core.

Due to potential backup- and recover errors, allow partially swapped
out struct ttm_tt's, although mark them as swapped out stopping them
from being swapped out a second time. More details in the ttm_pool.c
DOC section.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/ttm/ttm_pool.c | 391 +++++++++++++++++++++++++++++++--
 drivers/gpu/drm/ttm/ttm_tt.c   |  34 +++
 include/drm/ttm/ttm_pool.h     |   4 +
 include/drm/ttm/ttm_tt.h       |  19 ++
 4 files changed, 435 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
index 112438d965ff..f753e70a7c88 100644
--- a/drivers/gpu/drm/ttm/ttm_pool.c
+++ b/drivers/gpu/drm/ttm/ttm_pool.c
@@ -41,6 +41,7 @@
 #include <asm/set_memory.h>
 #endif
 
+#include <drm/ttm/ttm_backup.h>
 #include <drm/ttm/ttm_pool.h>
 #include <drm/ttm/ttm_tt.h>
 #include <drm/ttm/ttm_bo.h>
@@ -58,6 +59,32 @@ struct ttm_pool_dma {
 	unsigned long vaddr;
 };
 
+/**
+ * struct ttm_pool_tt_restore - State representing restore from backup
+ * @alloced_pages: Total number of already allocated pages for the ttm_tt.
+ * @restored_pages: Number of (sub) pages restored from swap for this
+ *		     chunk of 1 << @order pages.
+ * @first_page: The ttm page ptr representing for @old_pages[0].
+ * @caching_divide: Page pointer where subsequent pages are cached.
+ * @old_pages: Backup copy of page pointers that were replaced by the new
+ *	       page allocation.
+ * @pool: The pool used for page allocation while restoring.
+ * @order: The order of the last page allocated while restoring.
+ *
+ * Recovery from backup might fail when we've recovered less than the
+ * full ttm_tt. In order not to loose any data (yet), keep information
+ * around that allows us to restart a failed ttm backup recovery.
+ */
+struct ttm_pool_tt_restore {
+	pgoff_t alloced_pages;
+	pgoff_t restored_pages;
+	struct page **first_page;
+	struct page **caching_divide;
+	struct ttm_pool *pool;
+	unsigned int order;
+	struct page *old_pages[];
+};
+
 static unsigned long page_pool_size;
 
 MODULE_PARM_DESC(page_pool_size, "Number of pages in the WC/UC/DMA pool");
@@ -348,11 +375,102 @@ static unsigned int ttm_pool_page_order(struct ttm_pool *pool, struct page *p)
 	return p->private;
 }
 
+/*
+ * To be able to insert single pages into backup directly,
+ * we need to split multi-order page allocations and make them look
+ * like single-page allocations.
+ */
+static void ttm_pool_split_for_swap(struct ttm_pool *pool, struct page *p)
+{
+	unsigned int order = ttm_pool_page_order(pool, p);
+	pgoff_t nr;
+
+	if (!order)
+		return;
+
+	split_page(p, order);
+	nr = 1UL << order;
+	while (nr--)
+		(p++)->private = 0;
+}
+
+/**
+ * DOC: Partial backup and restoration of a struct ttm_tt.
+ *
+ * Swapout using ttm_backup::ops::backup_page() and swapin using
+ * ttm_backup::ops::copy_backed_up_page() may fail.
+ * The former most likely due to lack of swap-space or memory, the latter due
+ * to lack of memory or because of signal interruption during waits.
+ *
+ * Backupfailure is easily handled by using a ttm_tt pages vector that holds
+ * both swap entries and page pointers. This has to be taken into account when
+ * restoring such a ttm_tt from backup, and when freeing it while backed up.
+ * When restoring, for simplicity, new pages are actually allocated from the
+ * pool and the contents of any old pages are copied in and then the old pages
+ * are released.
+ *
+ * For restoration failures, the struct ttm_pool_tt_restore holds sufficient state
+ * to be able to resume an interrupted restore, and that structure is freed once
+ * the restoration is complete. If the struct ttm_tt is destroyed while there
+ * is a valid struct ttm_pool_tt_restore attached, that is also properly taken
+ * care of.
+ */
+
+static bool ttm_pool_restore_valid(const struct ttm_pool_tt_restore *restore)
+{
+	return restore && restore->restored_pages < (1 << restore->order);
+}
+
+static int ttm_pool_restore_tt(struct ttm_pool_tt_restore *restore,
+			       struct ttm_backup *backup,
+			       struct ttm_operation_ctx *ctx)
+{
+	unsigned int i, nr = 1 << restore->order;
+	int ret = 0;
+
+	if (!ttm_pool_restore_valid(restore))
+		return 0;
+
+	for (i = restore->restored_pages; i < nr; ++i) {
+		struct page *p = restore->old_pages[i];
+
+		if (ttm_backup_page_ptr_is_handle(p)) {
+			unsigned long handle = ttm_backup_page_ptr_to_handle(p);
+
+			if (handle == 0)
+				continue;
+
+			ret = backup->ops->copy_backed_up_page
+				(backup, restore->first_page[i],
+				 handle, ctx->interruptible);
+			if (ret)
+				break;
+
+			backup->ops->drop(backup, handle);
+		} else if (p) {
+			/*
+			 * We could probably avoid splitting the old page
+			 * using clever logic, but ATM we don't care.
+			 */
+			ttm_pool_split_for_swap(restore->pool, p);
+			copy_highpage(restore->first_page[i], p);
+			__free_pages(p, 0);
+		}
+
+		restore->restored_pages++;
+		restore->old_pages[i] = NULL;
+		cond_resched();
+	}
+
+	return ret;
+}
+
 /* Called when we got a page, either from a pool or newly allocated */
 static int ttm_pool_page_allocated(struct ttm_pool *pool, unsigned int order,
 				   struct page *p, dma_addr_t **dma_addr,
 				   unsigned long *num_pages,
-				   struct page ***pages)
+				   struct page ***pages,
+				   struct ttm_pool_tt_restore *restore)
 {
 	unsigned int i;
 	int r;
@@ -363,6 +481,16 @@ static int ttm_pool_page_allocated(struct ttm_pool *pool, unsigned int order,
 			return r;
 	}
 
+	if (restore) {
+		memcpy(restore->old_pages, *pages,
+		       (1 << order) * sizeof(*restore->old_pages));
+		memset(*pages, 0, (1 << order) * sizeof(**pages));
+		restore->order = order;
+		restore->restored_pages = 0;
+		restore->first_page = *pages;
+		restore->alloced_pages += 1UL << order;
+	}
+
 	*num_pages -= 1 << order;
 	for (i = 1 << order; i; --i, ++(*pages), ++p)
 		**pages = p;
@@ -388,22 +516,39 @@ static void ttm_pool_free_range(struct ttm_pool *pool, struct ttm_tt *tt,
 				pgoff_t start_page, pgoff_t end_page)
 {
 	struct page **pages = &tt->pages[start_page];
+	struct ttm_backup *backup = tt->backup;
 	unsigned int order;
 	pgoff_t i, nr;
 
 	for (i = start_page; i < end_page; i += nr, pages += nr) {
 		struct ttm_pool_type *pt = NULL;
+		struct page *p = *pages;
+
+		if (ttm_backup_page_ptr_is_handle(p)) {
+			unsigned long handle = ttm_backup_page_ptr_to_handle(p);
+
+			nr = 1;
+			if (handle != 0)
+				backup->ops->drop(backup, handle);
+			continue;
+		}
 
-		order = ttm_pool_page_order(pool, *pages);
-		nr = (1UL << order);
-		if (tt->dma_address)
-			ttm_pool_unmap(pool, tt->dma_address[i], nr);
+		if (pool) {
+			order = ttm_pool_page_order(pool, p);
+			nr = (1UL << order);
+			if (tt->dma_address)
+				ttm_pool_unmap(pool, tt->dma_address[i], nr);
+
+			pt = ttm_pool_select_type(pool, caching, order);
+		} else {
+			order = p->private;
+			nr = (1UL << order);
+		}
 
-		pt = ttm_pool_select_type(pool, caching, order);
 		if (pt)
-			ttm_pool_type_give(pt, *pages);
+			ttm_pool_type_give(pt, p);
 		else
-			ttm_pool_free_page(pool, caching, order, *pages);
+			ttm_pool_free_page(pool, caching, order, p);
 	}
 }
 
@@ -447,9 +592,37 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
 	else
 		gfp_flags |= GFP_HIGHUSER;
 
-	for (order = min_t(unsigned int, MAX_PAGE_ORDER, __fls(num_pages));
-	     num_pages;
-	     order = min_t(unsigned int, order, __fls(num_pages))) {
+	order = min_t(unsigned int, MAX_PAGE_ORDER, __fls(num_pages));
+
+	if (tt->page_flags & TTM_TT_FLAG_PRIV_BACKED_UP) {
+		if (!tt->restore) {
+			gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
+
+			if (ctx->gfp_retry_mayfail)
+				gfp |= __GFP_RETRY_MAYFAIL;
+
+			tt->restore =
+				kvzalloc(struct_size(tt->restore, old_pages,
+						     (size_t)1 << order), gfp);
+			/* RFC: Possibly loop on -ENOMEM and reduce order. */
+			if (!tt->restore)
+				return -ENOMEM;
+		} else if (ttm_pool_restore_valid(tt->restore)) {
+			struct ttm_pool_tt_restore *restore = tt->restore;
+
+			num_pages -= restore->alloced_pages;
+			order = min_t(unsigned int, order, __fls(num_pages));
+			pages += restore->alloced_pages;
+			r = ttm_pool_restore_tt(restore, tt->backup, ctx);
+			if (r)
+				return r;
+			caching = restore->caching_divide;
+		}
+
+		tt->restore->pool = pool;
+	}
+
+	for (; num_pages; order = min_t(unsigned int, order, __fls(num_pages))) {
 		struct ttm_pool_type *pt;
 
 		page_caching = tt->caching;
@@ -466,11 +639,19 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
 				r = ttm_pool_page_allocated(pool, order, p,
 							    &dma_addr,
 							    &num_pages,
-							    &pages);
+							    &pages,
+							    tt->restore);
 				if (r)
 					goto error_free_page;
 
 				caching = pages;
+				if (ttm_pool_restore_valid(tt->restore)) {
+					r = ttm_pool_restore_tt(tt->restore, tt->backup,
+								ctx);
+					if (r)
+						goto error_free_all;
+				}
+
 				if (num_pages < (1 << order))
 					break;
 
@@ -490,9 +671,17 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
 				caching = pages;
 			}
 			r = ttm_pool_page_allocated(pool, order, p, &dma_addr,
-						    &num_pages, &pages);
+						    &num_pages, &pages,
+						    tt->restore);
 			if (r)
 				goto error_free_page;
+
+			if (ttm_pool_restore_valid(tt->restore)) {
+				r = ttm_pool_restore_tt(tt->restore, tt->backup, ctx);
+				if (r)
+					goto error_free_all;
+			}
+
 			if (PageHighMem(p))
 				caching = pages;
 		}
@@ -511,12 +700,26 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
 	if (r)
 		goto error_free_all;
 
+	if (tt->restore) {
+		kvfree(tt->restore);
+		tt->restore = NULL;
+	}
+
+	if (tt->page_flags & TTM_TT_FLAG_PRIV_BACKED_UP)
+		tt->page_flags &= ~(TTM_TT_FLAG_PRIV_BACKED_UP |
+				    TTM_TT_FLAG_SWAPPED);
+
 	return 0;
 
 error_free_page:
 	ttm_pool_free_page(pool, page_caching, order, p);
 
 error_free_all:
+	if (tt->page_flags & TTM_TT_FLAG_PRIV_BACKED_UP) {
+		tt->restore->caching_divide = caching;
+		return r;
+	}
+
 	num_pages = tt->num_pages - num_pages;
 	caching_divide = caching - tt->pages;
 	ttm_pool_free_range(pool, tt, tt->caching, 0, caching_divide);
@@ -543,6 +746,168 @@ void ttm_pool_free(struct ttm_pool *pool, struct ttm_tt *tt)
 }
 EXPORT_SYMBOL(ttm_pool_free);
 
+/**
+ * ttm_pool_release_backed_up() - Release content of a swapped-out struct ttm_tt
+ * @tt: The struct ttm_tt.
+ *
+ * Release handles with associated content or any remaining pages of
+ * a backed-up struct ttm_tt.
+ */
+void ttm_pool_release_backed_up(struct ttm_tt *tt)
+{
+	struct ttm_backup *backup = tt->backup;
+	struct ttm_pool_tt_restore *restore;
+	pgoff_t i, start_page = 0;
+	unsigned long handle;
+
+	if (!(tt->page_flags & TTM_TT_FLAG_PRIV_BACKED_UP))
+		return;
+
+	restore = tt->restore;
+
+	if (ttm_pool_restore_valid(restore)) {
+		pgoff_t nr = 1UL << restore->order;
+
+		for (i = restore->restored_pages; i < nr; ++i) {
+			struct page *p = restore->old_pages[i];
+
+			if (ttm_backup_page_ptr_is_handle(p)) {
+				handle = ttm_backup_page_ptr_to_handle(p);
+				if (handle == 0)
+					continue;
+
+				backup->ops->drop(backup, handle);
+			} else if (p) {
+				ttm_pool_split_for_swap(restore->pool, p);
+				__free_pages(p, 0);
+			}
+		}
+	}
+
+	if (restore) {
+		pgoff_t mid = restore->caching_divide - tt->pages;
+
+		start_page = restore->alloced_pages;
+		/* Pages that might be dma-mapped and non-cached */
+		ttm_pool_free_range(restore->pool, tt, tt->caching,
+				    0, mid);
+		/* Pages that might be dma-mapped but cached */
+		ttm_pool_free_range(restore->pool, tt, ttm_cached,
+				    mid, restore->alloced_pages);
+	}
+
+	/* Shrunken pages. Cached and not dma-mapped. */
+	ttm_pool_free_range(NULL, tt, ttm_cached, start_page, tt->num_pages);
+
+	if (restore) {
+		kvfree(restore);
+		tt->restore = NULL;
+	}
+
+	tt->page_flags &= ~(TTM_TT_FLAG_PRIV_BACKED_UP | TTM_TT_FLAG_SWAPPED);
+}
+
+/**
+ * ttm_pool_back_up_tt() - Back up or purge a struct ttm_tt
+ * @pool: The pool used when allocating the struct ttm_tt.
+ * @ttm: The struct ttm_tt.
+ * @purge: Don't back up but release pages directly to system.
+ *
+ * Back up or purge a struct ttm_tt. If @purge is true, then
+ * all pages will be freed directly to the system rather than to the pool
+ * they were allocated from, making the function behave similarly to
+ * ttm_pool_free(). If @purge is false the pages will be backed up instead,
+ * exchanged for handles.
+ * A subsequent call to ttm_pool_alloc() will then read back the content and
+ * a subsequent call to ttm_pool_release_shrunken() will drop it.
+ * If backup of a page fails for whatever reason, @ttm will still be
+ * partially backed up, retaining those pages for which backup fails.
+ *
+ * Return: Number of pages actually backed up or freed, or negative
+ * error code on error.
+ */
+long ttm_pool_back_up_tt(struct ttm_pool *pool, struct ttm_tt *ttm, bool purge)
+{
+	struct ttm_backup *backup = ttm->backup;
+	struct page *page;
+	unsigned long handle;
+	gfp_t alloc_gfp;
+	gfp_t gfp;
+	int ret = 0;
+	pgoff_t shrunken = 0;
+	pgoff_t i, num_pages;
+
+	if ((!get_nr_swap_pages() && purge) ||
+	    pool->use_dma_alloc ||
+	    (ttm->page_flags & TTM_TT_FLAG_PRIV_BACKED_UP))
+		return -EBUSY;
+
+#ifdef CONFIG_X86
+	/* Anything returned to the system needs to be cached. */
+	if (ttm->caching != ttm_cached)
+		set_pages_array_wb(ttm->pages, ttm->num_pages);
+#endif
+
+	if (ttm->dma_address || purge) {
+		for (i = 0; i < ttm->num_pages; i += num_pages) {
+			unsigned int order;
+
+			page = ttm->pages[i];
+			if (unlikely(!page))
+				continue;
+
+			order = 1UL << ttm_pool_page_order(pool, page);
+			num_pages = 1UL << order;
+			if (ttm->dma_address)
+				ttm_pool_unmap(pool, ttm->dma_address[i],
+					       num_pages);
+			if (purge) {
+				shrunken += num_pages;
+				__free_pages(page, order);
+				memset(ttm->pages + i, 0,
+				       num_pages * sizeof(*ttm->pages));
+			}
+		}
+	}
+
+	if (purge)
+		return shrunken;
+
+	if (pool->use_dma32)
+		gfp = GFP_DMA32;
+	else
+		gfp = GFP_HIGHUSER;
+
+	alloc_gfp = GFP_KERNEL | __GFP_HIGH | __GFP_NOWARN | __GFP_RETRY_MAYFAIL;
+
+	for (i = 0; i < ttm->num_pages; ++i) {
+		page = ttm->pages[i];
+		if (unlikely(!page))
+			continue;
+
+		ttm_pool_split_for_swap(pool, page);
+
+		set_page_dirty_lock(page);
+		handle = backup->ops->backup_page(backup, page, false, i, gfp, alloc_gfp);
+		if (handle) {
+			ttm->pages[i] = ttm_backup_handle_to_page_ptr(handle);
+			put_page(page);
+			shrunken++;
+		} else {
+			/* We allow partially shrunken tts */
+			ret = -ENOMEM;
+			break;
+		}
+		cond_resched();
+	}
+
+	if (shrunken)
+		ttm->page_flags |= (TTM_TT_FLAG_PRIV_BACKED_UP |
+				    TTM_TT_FLAG_SWAPPED);
+
+	return shrunken ? shrunken : ret;
+}
+
 /**
  * ttm_pool_init - Initialize a pool
  *
diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
index 578a7c37f00b..e8779683e191 100644
--- a/drivers/gpu/drm/ttm/ttm_tt.c
+++ b/drivers/gpu/drm/ttm/ttm_tt.c
@@ -39,6 +39,7 @@
 #include <drm/drm_cache.h>
 #include <drm/drm_device.h>
 #include <drm/drm_util.h>
+#include <drm/ttm/ttm_backup.h>
 #include <drm/ttm/ttm_bo.h>
 #include <drm/ttm/ttm_tt.h>
 
@@ -157,6 +158,7 @@ static void ttm_tt_init_fields(struct ttm_tt *ttm,
 	ttm->swap_storage = NULL;
 	ttm->sg = bo->sg;
 	ttm->caching = caching;
+	ttm->restore = NULL;
 }
 
 int ttm_tt_init(struct ttm_tt *ttm, struct ttm_buffer_object *bo,
@@ -181,6 +183,12 @@ void ttm_tt_fini(struct ttm_tt *ttm)
 		fput(ttm->swap_storage);
 	ttm->swap_storage = NULL;
 
+	ttm_pool_release_backed_up(ttm);
+	if (ttm->backup) {
+		ttm->backup->ops->fini(ttm->backup);
+		ttm->backup = NULL;
+	}
+
 	if (ttm->pages)
 		kvfree(ttm->pages);
 	else
@@ -251,6 +259,32 @@ int ttm_tt_swapin(struct ttm_tt *ttm)
 	return ret;
 }
 
+/**
+ * ttm_tt_back_up() - Helper to back up a struct ttm_tt.
+ * @bdev: The TTM device.
+ * @tt: The struct ttm_tt.
+ * @purge: Don't back up but release pages directly to system,
+ * bypassing any pooling.
+ *
+ * Helper for a TTM driver to use from the bo_shrink() method to shrink
+ * a struct ttm_tt, after it has done the necessary unbinding. This function
+ * will update the page accounting and call ttm_pool_shrink_tt to free pages
+ * or move them to the swap cache.
+ *
+ * Return: Number of pages freed or swapped out, or negative error code on
+ * error.
+ */
+long ttm_tt_back_up(struct ttm_device *bdev, struct ttm_tt *tt, bool purge)
+{
+	long ret = ttm_pool_back_up_tt(&bdev->pool, tt, purge);
+
+	if (ret > 0)
+		tt->page_flags &= ~TTM_TT_FLAG_PRIV_POPULATED;
+
+	return ret;
+}
+EXPORT_SYMBOL(ttm_tt_back_up);
+
 /**
  * ttm_tt_swapout - swap out tt object
  *
diff --git a/include/drm/ttm/ttm_pool.h b/include/drm/ttm/ttm_pool.h
index 160d954a261e..c7f9383be3cc 100644
--- a/include/drm/ttm/ttm_pool.h
+++ b/include/drm/ttm/ttm_pool.h
@@ -89,6 +89,10 @@ void ttm_pool_fini(struct ttm_pool *pool);
 
 int ttm_pool_debugfs(struct ttm_pool *pool, struct seq_file *m);
 
+void ttm_pool_release_backed_up(struct ttm_tt *tt);
+
+long ttm_pool_back_up_tt(struct ttm_pool *pool, struct ttm_tt *ttm, bool purge);
+
 int ttm_pool_mgr_init(unsigned long num_pages);
 void ttm_pool_mgr_fini(void);
 
diff --git a/include/drm/ttm/ttm_tt.h b/include/drm/ttm/ttm_tt.h
index 2b9d856ff388..5dca56d50f06 100644
--- a/include/drm/ttm/ttm_tt.h
+++ b/include/drm/ttm/ttm_tt.h
@@ -32,11 +32,13 @@
 #include <drm/ttm/ttm_caching.h>
 #include <drm/ttm/ttm_kmap_iter.h>
 
+struct ttm_backup;
 struct ttm_device;
 struct ttm_tt;
 struct ttm_resource;
 struct ttm_buffer_object;
 struct ttm_operation_ctx;
+struct ttm_pool_tt_restore;
 
 /**
  * struct ttm_tt - This is a structure holding the pages, caching- and aperture
@@ -85,6 +87,9 @@ struct ttm_tt {
 	 * fault handling abuses the DMA api a bit and dma_map_attrs can't be
 	 * used to assure pgprot always matches.
 	 *
+	 * TTM_TT_FLAG_PRIV_BACKED_UP: TTM internal only. This is set if the
+	 * struct ttm_tt has been (possibly partially) backed up.
+	 *
 	 * TTM_TT_FLAG_PRIV_POPULATED: TTM internal only. DO NOT USE. This is
 	 * set by TTM after ttm_tt_populate() has successfully returned, and is
 	 * then unset when TTM calls ttm_tt_unpopulate().
@@ -96,6 +101,7 @@ struct ttm_tt {
 #define TTM_TT_FLAG_DECRYPTED		BIT(4)
 
 #define TTM_TT_FLAG_PRIV_POPULATED	BIT(5)
+#define TTM_TT_FLAG_PRIV_BACKED_UP	BIT(6)
 	uint32_t page_flags;
 	/** @num_pages: Number of pages in the page array. */
 	uint32_t num_pages;
@@ -105,11 +111,21 @@ struct ttm_tt {
 	dma_addr_t *dma_address;
 	/** @swap_storage: Pointer to shmem struct file for swap storage. */
 	struct file *swap_storage;
+	/**
+	 * @backup: Pointer to backup struct for backed up tts.
+	 * RFC: Could possibly be unified with @swap_storage.
+	 */
+	struct ttm_backup *backup;
 	/**
 	 * @caching: The current caching state of the pages, see enum
 	 * ttm_caching.
 	 */
 	enum ttm_caching caching;
+	/**
+	 * @restore: Partial restoration from backup state.
+	 * RFC: Incorporate in struct ttm_backup?
+	 */
+	struct ttm_pool_tt_restore *restore;
 };
 
 /**
@@ -230,6 +246,9 @@ void ttm_tt_mgr_init(unsigned long num_pages, unsigned long num_dma32_pages);
 struct ttm_kmap_iter *ttm_kmap_iter_tt_init(struct ttm_kmap_iter_tt *iter_tt,
 					    struct ttm_tt *tt);
 unsigned long ttm_tt_pages_limit(void);
+
+long ttm_tt_back_up(struct ttm_device *bdev, struct ttm_tt *tt, bool purge);
+
 #if IS_ENABLED(CONFIG_AGP)
 #include <linux/agp_backend.h>
 
-- 
2.44.0

[RFC PATCH 7/8] drm/xe, drm/ttm: Provide a generic LRU walker helper

[Thomas Hellström]

Export the needed functions from TTM and provide a generic LRU
walker in xe, in the spirit of drm_gem_lru_scan() but building
on the restartable TTM LRU functionality.

The LRU walker optionally supports locking objects as part of
a drm_exec locking transaction, and can thus be used for both
exhaustive eviction and shrinking. And, in fact, direct
shrinking in the case where we fail to populate system memory
objects and want to retry by shrinking purgeable or evictable
local objects, which a shrinker is not capable of doing.

The LRU walker helper can easily be moved to TTM when / if used
by other drivers.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/ttm/ttm_resource.c  |   3 +
 drivers/gpu/drm/xe/Makefile         |   1 +
 drivers/gpu/drm/xe/xe_ttm_helpers.c | 150 ++++++++++++++++++++++++++++
 drivers/gpu/drm/xe/xe_ttm_helpers.h |  60 +++++++++++
 4 files changed, 214 insertions(+)
 create mode 100644 drivers/gpu/drm/xe/xe_ttm_helpers.c
 create mode 100644 drivers/gpu/drm/xe/xe_ttm_helpers.h

diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
index 89f19fb6e2b3..4cad467983f8 100644
--- a/drivers/gpu/drm/ttm/ttm_resource.c
+++ b/drivers/gpu/drm/ttm/ttm_resource.c
@@ -106,6 +106,7 @@ void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor)
 	ttm_resource_cursor_fini_locked(cursor);
 	spin_unlock(lru_lock);
 }
+EXPORT_SYMBOL(ttm_resource_cursor_fini);
 
 /**
  * ttm_lru_bulk_move_init - initialize a bulk move structure
@@ -635,6 +636,7 @@ ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
 
 	return NULL;
 }
+EXPORT_SYMBOL(ttm_resource_manager_next);
 
 /**
  * ttm_resource_manager_first() - Start iterating over the resources
@@ -661,6 +663,7 @@ ttm_resource_manager_first(struct ttm_resource_manager *man,
 
 	return ttm_resource_manager_next(cursor);
 }
+EXPORT_SYMBOL(ttm_resource_manager_first);
 
 static void ttm_kmap_iter_iomap_map_local(struct ttm_kmap_iter *iter,
 					  struct iosys_map *dmap,
diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
index 705c0eaf6e71..ecd7dde9cbbe 100644
--- a/drivers/gpu/drm/xe/Makefile
+++ b/drivers/gpu/drm/xe/Makefile
@@ -133,6 +133,7 @@ xe-y += xe_bb.o \
 	xe_tile.o \
 	xe_tile_sysfs.o \
 	xe_trace.o \
+	xe_ttm_helpers.o \
 	xe_ttm_sys_mgr.o \
 	xe_ttm_stolen_mgr.o \
 	xe_ttm_vram_mgr.o \
diff --git a/drivers/gpu/drm/xe/xe_ttm_helpers.c b/drivers/gpu/drm/xe/xe_ttm_helpers.c
new file mode 100644
index 000000000000..7b08bfd912c8
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_ttm_helpers.c
@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#include <drm/drm_exec.h>
+
+#include "xe_ttm_helpers.h"
+
+#include <drm/ttm/ttm_bo.h>
+#include <drm/ttm/ttm_device.h>
+
+static bool xe_ttm_lru_walk_trylock(struct xe_ttm_lru_walk *walk,
+				    struct ttm_buffer_object *bo,
+				    bool *needs_unlock)
+{
+	struct ttm_operation_ctx *ctx = walk->ctx;
+
+	*needs_unlock = false;
+
+	if (!walk->exec && dma_resv_trylock(bo->base.resv)) {
+		*needs_unlock = true;
+		return true;
+	}
+
+	if (bo->base.resv == ctx->resv && ctx->allow_res_evict) {
+		dma_resv_assert_held(bo->base.resv);
+		return true;
+	}
+
+	return false;
+}
+
+static void xe_ttm_lru_walk_unlock(struct ttm_buffer_object *bo, bool locked)
+{
+	if (locked)
+		dma_resv_unlock(bo->base.resv);
+}
+
+/**
+ * xe_ttm_lru_walk_for_evict() - Perform a LRU list walk, with actions taken on
+ * valid items.
+ * @walk: describe the walks and actions taken
+ * @bdev: The TTM device.
+ * @man: The struct ttm_resource manager whose LRU lists we're walking.
+ * @mem_type: The memory type associated with @man.
+ * @target: The end condition for the walk.
+ *
+ * The LRU lists of @man are walk, and for each struct ttm_resource encountered,
+ * the corresponding ttm_buffer_object is locked and taken a reference on, and
+ * the LRU lock is dropped. the LRU lock may be dropped before locking and, in
+ * that case, it's verified that the item actually remains on the LRU list after
+ * the lock, and that the buffer object hasn't changed.
+ *
+ * With a locked object, the actions indicated by @walk->allow_bo() and
+ * @walk->process_bo are performed. (RFC: Combine these?), and after that, the
+ * bo is unlocked, the refcount dropped and the next struct ttm_resource is
+ * processed. Here we rely on TTM's restartable LRU list implementation.
+ *
+ * Typically @walk->process_bo() would return the number of pages evicted, and
+ * that when the total exceeds @target, or when the LRU list has been walked
+ * in full, iteration is terminated. It's also terminated on error.
+ *
+ * Buffer object dma_resv locking:
+ * This locking is performed using the combined interpretation of @walk->exec and
+ * @walk->ctx according to the following.
+ * 1) Sleeping locks: Sleeping locks are used exclusively if @walk->exec is true.
+ * The buffer object are not unlocked. That is the caller's responsibility.
+ * 2) Assuming bo is already locked: This assumption is made iff @walk->exec is false,
+ * @walk->ctx->allow_res_evict is true and bo->base.resv == @walk->ctx->resv.
+ * This is for cases where it is desired to evict bos sharing a reservation lock
+ * that is already held by the process. Thes bo locks are not unlocked during
+ * the walk.
+ * 3) Trylocking. Trylocking is done in all other cases. If trylocking fails, the
+ * iteration skips the current item and continues. Trylocks are always unlocked
+ * by the walk.
+ *
+ * Note that the way dma_resv individualization is done, locking needs to be done
+ * either with the LRU lock held (trylocking only) or with a reference on the
+ * object.
+ *
+ * Return: (Typically) The number of pages evicted or negative error code on error.
+ */
+long xe_ttm_lru_walk_for_evict(struct xe_ttm_lru_walk *walk, struct ttm_device *bdev,
+			       struct ttm_resource_manager *man, unsigned int mem_type,
+			       long target)
+{
+	struct drm_exec *exec = walk->exec;
+	struct ttm_resource_cursor cursor;
+	struct ttm_resource *res;
+	long sofar = 0;
+	long lret;
+	int ret;
+
+	spin_lock(&bdev->lru_lock);
+	ttm_resource_manager_for_each_res(man, &cursor, res) {
+		struct ttm_buffer_object *bo = res->bo;
+		bool bo_needs_unlock = false;
+		bool bo_locked = false;
+
+		if (!bo || bo->resource != res)
+			continue;
+
+		if (xe_ttm_lru_walk_trylock(walk, bo, &bo_needs_unlock))
+			bo_locked = true;
+		else if (!exec)
+			continue;
+
+		if (!ttm_bo_get_unless_zero(bo)) {
+			xe_ttm_lru_walk_unlock(bo, bo_needs_unlock);
+			continue;
+		}
+
+		spin_unlock(&bdev->lru_lock);
+
+		if (!bo_locked) {
+			ret = drm_exec_lock_obj(exec, &bo->base);
+			if (ret)
+				ttm_bo_put(bo);
+		}
+
+		lret = 0;
+
+		/*
+		 * Note that in between the release of the lru lock and the
+		 * drm_exec_lock_obj, the bo may have switched resource,
+		 * and also memory type. In that case we just skip it.
+		 */
+		if (bo->resource == res && res->mem_type == mem_type &&
+		    walk->ops->allow_bo(walk, bo, mem_type))
+			lret = walk->ops->process_bo(walk, bo);
+
+		xe_ttm_lru_walk_unlock(bo, bo_needs_unlock);
+		ttm_bo_put(bo);
+		if (lret < 0) {
+			sofar = lret;
+			goto out;
+		}
+
+		sofar += lret;
+		if (sofar >= target)
+			goto out;
+
+		spin_lock(&bdev->lru_lock);
+	}
+	spin_unlock(&bdev->lru_lock);
+out:
+	ttm_resource_cursor_fini(&cursor);
+	return sofar;
+}
diff --git a/drivers/gpu/drm/xe/xe_ttm_helpers.h b/drivers/gpu/drm/xe/xe_ttm_helpers.h
new file mode 100644
index 000000000000..a52887ce0241
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_ttm_helpers.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#ifndef _XE_TTM_HELPERS_H_
+#define _XE_TTM_HELPERS_H_
+
+#include <linux/types.h>
+
+struct drm_exec;
+struct ttm_device;
+struct ttm_buffer_object;
+struct ttm_operation_ctx;
+struct ttm_resource_manager;
+
+struct xe_ttm_lru_walk;
+
+/** struct xe_ttm_lru_walk_ops - Operations for a LRU walk. */
+struct xe_ttm_lru_walk_ops {
+	/**
+	 * allow_bo - Allow calling @process_bo for this bo.
+	 * @walk: struct xe_ttm_lru_walk describing the walk.
+	 * @bo: A locked and referenced buffer object.
+	 * @mem_type: The memory type of the LRU list.
+	 *
+	 * RFC: Combine these two functions?
+	 *
+	 * Return: true if @process_bo should be called, @false otherwise.
+	 */
+	bool (*allow_bo)(struct xe_ttm_lru_walk *walk, struct ttm_buffer_object *bo,
+			 unsigned int mem_type);
+
+	/**
+	 * process_bo - Process this bo.
+	 * @walk: struct xe_ttm_lru_walk describing the walk.
+	 * @bo: A locked and referenced buffer object.
+	 *
+	 * Return: Negative error code on error, Number of processed pages on
+	 * success. 0 also indicates success.
+	 */
+	long (*process_bo)(struct xe_ttm_lru_walk *walk, struct ttm_buffer_object *bo);
+};
+
+/**
+ * struct xe_ttm_lru_walk - Structure describing a LRU walk.
+ * @ops: Pointer to the ops structure.
+ * @ctx: Pointer to the struct ttm_operation_ctx.
+ * @exec: The struct drm_exec context for the WW transaction if any.
+ */
+struct xe_ttm_lru_walk {
+	const struct xe_ttm_lru_walk_ops *ops;
+	struct ttm_operation_ctx *ctx;
+	struct drm_exec *exec;
+};
+
+long xe_ttm_lru_walk_for_evict(struct xe_ttm_lru_walk *walk, struct ttm_device *bdev,
+			       struct ttm_resource_manager *man, unsigned int mem_type,
+			       long target);
+#endif
-- 
2.44.0

[RFC PATCH 8/8] drm/xe: Add a shrinker for xe bos

[Thomas Hellström]

Rather than relying on the TTM watermark accounting add a shrinker
for xe_bos in TT or system memory.

Leverage the newly added TTM per-page shrinking and shmem backup
support.

Although xe doesn't fully support WONTNEED (purgeable) bos yet,
introduce and add shrinker support for purgeable ttm_tts.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/xe/Makefile          |   1 +
 drivers/gpu/drm/xe/xe_bo.c           | 123 ++++++++++++--
 drivers/gpu/drm/xe/xe_bo.h           |   3 +
 drivers/gpu/drm/xe/xe_device.c       |   8 +
 drivers/gpu/drm/xe/xe_device_types.h |   2 +
 drivers/gpu/drm/xe/xe_shrinker.c     | 237 +++++++++++++++++++++++++++
 drivers/gpu/drm/xe/xe_shrinker.h     |  18 ++
 drivers/gpu/drm/xe/xe_ttm_helpers.c  |  74 +++++++++
 drivers/gpu/drm/xe/xe_ttm_helpers.h  |   3 +
 9 files changed, 452 insertions(+), 17 deletions(-)
 create mode 100644 drivers/gpu/drm/xe/xe_shrinker.c
 create mode 100644 drivers/gpu/drm/xe/xe_shrinker.h

diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
index ecd7dde9cbbe..2a8f29a98db7 100644
--- a/drivers/gpu/drm/xe/Makefile
+++ b/drivers/gpu/drm/xe/Makefile
@@ -128,6 +128,7 @@ xe-y += xe_bb.o \
 	xe_ring_ops.o \
 	xe_sa.o \
 	xe_sched_job.o \
+	xe_shrinker.o \
 	xe_step.o \
 	xe_sync.o \
 	xe_tile.o \
diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index 9298546909b5..42e29ef2a51e 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -10,6 +10,7 @@
 #include <drm/drm_drv.h>
 #include <drm/drm_gem_ttm_helper.h>
 #include <drm/drm_managed.h>
+#include <drm/ttm/ttm_backup.h>
 #include <drm/ttm/ttm_device.h>
 #include <drm/ttm/ttm_placement.h>
 #include <drm/ttm/ttm_tt.h>
@@ -24,7 +25,9 @@
 #include "xe_migrate.h"
 #include "xe_preempt_fence.h"
 #include "xe_res_cursor.h"
+#include "xe_shrinker.h"
 #include "xe_trace.h"
+#include "xe_ttm_helpers.h"
 #include "xe_ttm_stolen_mgr.h"
 #include "xe_vm.h"
 
@@ -263,11 +266,15 @@ static void xe_evict_flags(struct ttm_buffer_object *tbo,
 	}
 }
 
+/* struct xe_ttm_tt - Subclassed ttm_tt for xe */
 struct xe_ttm_tt {
 	struct ttm_tt ttm;
-	struct device *dev;
+	/** @xe - The xe device */
+	struct xe_device *xe;
 	struct sg_table sgt;
 	struct sg_table *sg;
+	/** @purgeable - Whether the bo is purgeable (WONTNEED) */
+	bool purgeable;
 };
 
 static int xe_tt_map_sg(struct ttm_tt *tt)
@@ -276,7 +283,8 @@ static int xe_tt_map_sg(struct ttm_tt *tt)
 	unsigned long num_pages = tt->num_pages;
 	int ret;
 
-	XE_WARN_ON(tt->page_flags & TTM_TT_FLAG_EXTERNAL);
+	XE_WARN_ON((tt->page_flags & TTM_TT_FLAG_EXTERNAL) &&
+		   !(tt->page_flags & TTM_TT_FLAG_EXTERNAL_MAPPABLE));
 
 	if (xe_tt->sg)
 		return 0;
@@ -284,13 +292,13 @@ static int xe_tt_map_sg(struct ttm_tt *tt)
 	ret = sg_alloc_table_from_pages_segment(&xe_tt->sgt, tt->pages,
 						num_pages, 0,
 						(u64)num_pages << PAGE_SHIFT,
-						xe_sg_segment_size(xe_tt->dev),
+						xe_sg_segment_size(xe_tt->xe->drm.dev),
 						GFP_KERNEL);
 	if (ret)
 		return ret;
 
 	xe_tt->sg = &xe_tt->sgt;
-	ret = dma_map_sgtable(xe_tt->dev, xe_tt->sg, DMA_BIDIRECTIONAL,
+	ret = dma_map_sgtable(xe_tt->xe->drm.dev, xe_tt->sg, DMA_BIDIRECTIONAL,
 			      DMA_ATTR_SKIP_CPU_SYNC);
 	if (ret) {
 		sg_free_table(xe_tt->sg);
@@ -309,21 +317,41 @@ struct sg_table *xe_bo_sg(struct xe_bo *bo)
 	return xe_tt->sg;
 }
 
+/*
+ * Account ttm pages against the device shrinker's shrinkable and
+ * purgeable counts.
+ */
+static void xe_ttm_tt_account(struct ttm_tt *tt, bool add)
+{
+	struct xe_ttm_tt *xe_tt = container_of(tt, struct xe_ttm_tt, ttm);
+	long num_pages = tt->num_pages;
+
+	if (!add)
+		num_pages = -num_pages;
+
+	if (xe_tt->purgeable)
+		xe_shrinker_mod_pages(xe_tt->xe->mem.shrinker, 0, num_pages);
+	else
+		xe_shrinker_mod_pages(xe_tt->xe->mem.shrinker, num_pages, 0);
+}
+
 static struct ttm_tt *xe_ttm_tt_create(struct ttm_buffer_object *ttm_bo,
 				       u32 page_flags)
 {
 	struct xe_bo *bo = ttm_to_xe_bo(ttm_bo);
 	struct xe_device *xe = xe_bo_device(bo);
-	struct xe_ttm_tt *tt;
+	struct xe_ttm_tt *xe_tt;
+	struct ttm_tt *tt;
 	unsigned long extra_pages;
 	enum ttm_caching caching;
 	int err;
 
-	tt = kzalloc(sizeof(*tt), GFP_KERNEL);
-	if (!tt)
+	xe_tt = kzalloc(sizeof(*xe_tt), GFP_KERNEL);
+	if (!xe_tt)
 		return NULL;
 
-	tt->dev = xe->drm.dev;
+	tt = &xe_tt->ttm;
+	xe_tt->xe = xe;
 
 	extra_pages = 0;
 	if (xe_bo_needs_ccs_pages(bo))
@@ -351,13 +379,23 @@ static struct ttm_tt *xe_ttm_tt_create(struct ttm_buffer_object *ttm_bo,
 	    (xe->info.graphics_verx100 >= 1270 && bo->flags & XE_BO_PAGETABLE))
 		caching = ttm_write_combined;
 
-	err = ttm_tt_init(&tt->ttm, &bo->ttm, page_flags, caching, extra_pages);
+	if (ttm_bo->type != ttm_bo_type_sg)
+		page_flags |= TTM_TT_FLAG_EXTERNAL | TTM_TT_FLAG_EXTERNAL_MAPPABLE;
+
+	err = ttm_tt_init(tt, &bo->ttm, page_flags, caching, extra_pages);
 	if (err) {
-		kfree(tt);
+		kfree(xe_tt);
 		return NULL;
 	}
 
-	return &tt->ttm;
+	tt->backup = ttm_backup_shmem_create(tt->num_pages << PAGE_SHIFT);
+	if (IS_ERR(tt->backup)) {
+		ttm_tt_fini(tt);
+		kfree(xe_tt);
+		return NULL;
+	}
+
+	return tt;
 }
 
 static int xe_ttm_tt_populate(struct ttm_device *ttm_dev, struct ttm_tt *tt,
@@ -369,7 +407,8 @@ static int xe_ttm_tt_populate(struct ttm_device *ttm_dev, struct ttm_tt *tt,
 	 * dma-bufs are not populated with pages, and the dma-
 	 * addresses are set up when moved to XE_PL_TT.
 	 */
-	if (tt->page_flags & TTM_TT_FLAG_EXTERNAL)
+	if ((tt->page_flags & TTM_TT_FLAG_EXTERNAL) &&
+	    !(tt->page_flags & TTM_TT_FLAG_EXTERNAL_MAPPABLE))
 		return 0;
 
 	err = ttm_pool_alloc(&ttm_dev->pool, tt, ctx);
@@ -378,27 +417,68 @@ static int xe_ttm_tt_populate(struct ttm_device *ttm_dev, struct ttm_tt *tt,
 
 	/* A follow up may move this xe_bo_move when BO is moved to XE_PL_TT */
 	err = xe_tt_map_sg(tt);
-	if (err)
+	if (err) {
 		ttm_pool_free(&ttm_dev->pool, tt);
+		return err;
+	}
 
-	return err;
+	xe_ttm_tt_account(tt, true);
+
+	return 0;
 }
 
 static void xe_ttm_tt_unpopulate(struct ttm_device *ttm_dev, struct ttm_tt *tt)
 {
 	struct xe_ttm_tt *xe_tt = container_of(tt, struct xe_ttm_tt, ttm);
+	struct xe_device *xe = xe_tt->xe;
 
-	if (tt->page_flags & TTM_TT_FLAG_EXTERNAL)
+	if ((tt->page_flags & TTM_TT_FLAG_EXTERNAL) &&
+	    !(tt->page_flags & TTM_TT_FLAG_EXTERNAL_MAPPABLE))
 		return;
 
 	if (xe_tt->sg) {
-		dma_unmap_sgtable(xe_tt->dev, xe_tt->sg,
+		dma_unmap_sgtable(xe->drm.dev, xe_tt->sg,
 				  DMA_BIDIRECTIONAL, 0);
 		sg_free_table(xe_tt->sg);
 		xe_tt->sg = NULL;
 	}
 
-	return ttm_pool_free(&ttm_dev->pool, tt);
+	ttm_pool_free(&ttm_dev->pool, tt);
+	xe_ttm_tt_account(tt, false);
+}
+
+/**
+ * xe_bo_shrinker_process - Try to shrink an xe bo.
+ * @walk:  - The walk parameters
+ * @bo: The TTM buffer object
+ *
+ * Try to shrink- or purge a bo, and if it succeeds, unmap dma.
+ *
+ * Return: The number of pages shrunken or purged, or negative error
+ * code on failure.
+ */
+long xe_bo_shrinker_process(struct xe_ttm_lru_walk *walk, struct ttm_buffer_object *bo)
+{
+	struct ttm_tt *tt = bo->ttm;
+	struct xe_ttm_tt *xe_tt = container_of(tt, struct xe_ttm_tt, ttm);
+	struct xe_device *xe = xe_tt->xe;
+	long lret;
+
+	lret = xe_ttm_bo_try_shrink(walk, bo, xe_tt->purgeable);
+	if (lret > 0) {
+		xe_assert(xe, !ttm_tt_is_populated(tt));
+
+		xe_ttm_tt_account(tt, false);
+
+		if (xe_tt->sg) {
+			dma_unmap_sgtable(xe->drm.dev, xe_tt->sg,
+					  DMA_BIDIRECTIONAL, 0);
+			sg_free_table(xe_tt->sg);
+			xe_tt->sg = NULL;
+		}
+	}
+
+	return lret;
 }
 
 static void xe_ttm_tt_destroy(struct ttm_device *ttm_dev, struct ttm_tt *tt)
@@ -1644,6 +1724,8 @@ int xe_bo_pin_external(struct xe_bo *bo)
 	}
 
 	ttm_bo_pin(&bo->ttm);
+	if (bo->ttm.ttm && ttm_tt_is_populated(bo->ttm.ttm))
+		xe_ttm_tt_account(bo->ttm.ttm, false);
 
 	/*
 	 * FIXME: If we always use the reserve / unreserve functions for locking
@@ -1702,6 +1784,8 @@ int xe_bo_pin(struct xe_bo *bo)
 	}
 
 	ttm_bo_pin(&bo->ttm);
+	if (bo->ttm.ttm && ttm_tt_is_populated(bo->ttm.ttm))
+		xe_ttm_tt_account(bo->ttm.ttm, false);
 
 	/*
 	 * FIXME: If we always use the reserve / unreserve functions for locking
@@ -1737,6 +1821,9 @@ void xe_bo_unpin_external(struct xe_bo *bo)
 	}
 
 	ttm_bo_unpin(&bo->ttm);
+	if (bo->ttm.ttm && ttm_tt_is_populated(bo->ttm.ttm))
+		xe_ttm_tt_account(bo->ttm.ttm, true);
+
 
 	/*
 	 * FIXME: If we always use the reserve / unreserve functions for locking
@@ -1766,6 +1853,8 @@ void xe_bo_unpin(struct xe_bo *bo)
 	}
 
 	ttm_bo_unpin(&bo->ttm);
+	if (bo->ttm.ttm && ttm_tt_is_populated(bo->ttm.ttm))
+		xe_ttm_tt_account(bo->ttm.ttm, true);
 }
 
 /**
diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h
index 52e441f77e96..3866ba9d4523 100644
--- a/drivers/gpu/drm/xe/xe_bo.h
+++ b/drivers/gpu/drm/xe/xe_bo.h
@@ -93,6 +93,7 @@
 #define XE_BO_PROPS_INVALID	(-1)
 
 struct sg_table;
+struct xe_ttm_lru_walk;
 
 struct xe_bo *xe_bo_alloc(void);
 void xe_bo_free(struct xe_bo *bo);
@@ -344,6 +345,8 @@ static inline unsigned int xe_sg_segment_size(struct device *dev)
 
 #define i915_gem_object_flush_if_display(obj)		((void)(obj))
 
+long xe_bo_shrinker_process(struct xe_ttm_lru_walk *walk, struct ttm_buffer_object *bo);
+
 #if IS_ENABLED(CONFIG_DRM_XE_KUNIT_TEST)
 /**
  * xe_bo_is_mem_type - Whether the bo currently resides in the given
diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
index b0bfe75eb59f..f05a9d8ed23d 100644
--- a/drivers/gpu/drm/xe/xe_device.c
+++ b/drivers/gpu/drm/xe/xe_device.c
@@ -38,6 +38,7 @@
 #include "xe_pcode.h"
 #include "xe_pm.h"
 #include "xe_query.h"
+#include "xe_shrinker.h"
 #include "xe_sriov.h"
 #include "xe_tile.h"
 #include "xe_ttm_stolen_mgr.h"
@@ -232,6 +233,9 @@ static void xe_device_destroy(struct drm_device *dev, void *dummy)
 	if (xe->unordered_wq)
 		destroy_workqueue(xe->unordered_wq);
 
+	if (!IS_ERR_OR_NULL(xe->mem.shrinker))
+		xe_shrinker_destroy(xe->mem.shrinker);
+
 	ttm_device_fini(&xe->ttm);
 }
 
@@ -261,6 +265,10 @@ struct xe_device *xe_device_create(struct pci_dev *pdev,
 	if (err)
 		goto err;
 
+	xe->mem.shrinker = xe_shrinker_create(xe);
+	if (IS_ERR(xe->mem.shrinker))
+		return ERR_CAST(xe->mem.shrinker);
+
 	xe->info.devid = pdev->device;
 	xe->info.revid = pdev->revision;
 	xe->info.force_execlist = xe_modparam.force_execlist;
diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
index 1df3dcc17d75..daafd7a910d7 100644
--- a/drivers/gpu/drm/xe/xe_device_types.h
+++ b/drivers/gpu/drm/xe/xe_device_types.h
@@ -315,6 +315,8 @@ struct xe_device {
 		struct xe_mem_region vram;
 		/** @mem.sys_mgr: system TTM manager */
 		struct ttm_resource_manager sys_mgr;
+		/** @mem.sys_mgr: system memory shrinker. */
+		struct xe_shrinker *shrinker;
 	} mem;
 
 	/** @sriov: device level virtualization data */
diff --git a/drivers/gpu/drm/xe/xe_shrinker.c b/drivers/gpu/drm/xe/xe_shrinker.c
new file mode 100644
index 000000000000..70c99259d57d
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_shrinker.c
@@ -0,0 +1,237 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#include <linux/shrinker.h>
+#include <linux/swap.h>
+
+#include <drm/ttm/ttm_bo.h>
+#include <drm/ttm/ttm_tt.h>
+
+#include "xe_bo.h"
+#include "xe_shrinker.h"
+#include "xe_ttm_helpers.h"
+
+/**
+ * struct xe_shrinker - per-device shrinker
+ * @xe: Back pointer to the device.
+ * @lock: Lock protecting accounting.
+ * @shrinkable_pages: Number of pages that are currently shrinkable.
+ * @purgeable_pages: Number of pages that are currently purgeable.
+ * @shrink: Pointer to the mm shrinker.
+ */
+struct xe_shrinker {
+	struct xe_device *xe;
+	rwlock_t lock;
+	long shrinkable_pages;
+	long purgeable_pages;
+	struct shrinker *shrink;
+};
+
+/**
+ * struct xe_shrink_lru_walk - lru_walk subclass for shrinker
+ * @walk: The embedded base class.
+ * @xe: Pointer to the xe device.
+ * @purge: Purgeable only request from the srinker.
+ */
+struct xe_shrink_lru_walk {
+	struct xe_ttm_lru_walk walk;
+	struct xe_device *xe;
+	bool purge;
+};
+
+static struct xe_shrinker *to_xe_shrinker(struct shrinker *shrink)
+{
+	return shrink->private_data;
+}
+
+static struct xe_shrink_lru_walk *
+to_xe_shrink_lru_walk(struct xe_ttm_lru_walk *walk)
+{
+	return container_of(walk, struct xe_shrink_lru_walk, walk);
+}
+
+/**
+ * xe_shrinker_mod_pages() - Modify shrinker page accounting
+ * @shrinker: Pointer to the struct xe_shrinker.
+ * @shrinkable: Shrinkable pages delta. May be negative.
+ * @purgeable: Purgeable page delta. May be negative.
+ *
+ * Modifies the shrinkable and purgeable pages accounting.
+ */
+void
+xe_shrinker_mod_pages(struct xe_shrinker *shrinker, long shrinkable, long purgeable)
+{
+	write_lock(&shrinker->lock);
+	shrinker->shrinkable_pages += shrinkable;
+	shrinker->purgeable_pages += purgeable;
+	write_unlock(&shrinker->lock);
+}
+
+static bool xe_shrinker_allow_bo(struct xe_ttm_lru_walk *walk,
+				 struct ttm_buffer_object *bo,
+				 unsigned int mem_type)
+{
+	struct xe_shrink_lru_walk *shrink_walk = to_xe_shrink_lru_walk(walk);
+	struct ttm_place place = {.mem_type = mem_type};
+	struct ttm_tt *tt = bo->ttm;
+	bool ret;
+
+	if (!tt || !ttm_tt_is_populated(tt) ||
+	    !(tt->page_flags & TTM_TT_FLAG_EXTERNAL_MAPPABLE))
+		return false;
+
+	if (shrink_walk->purge)
+		return false;
+
+	ret = ttm_bo_eviction_valuable(bo, &place);
+
+	return ret;
+}
+
+static long xe_shrinker_walk(struct xe_shrink_lru_walk *shrink_walk, long target)
+{
+	struct xe_device *xe = shrink_walk->xe;
+	struct ttm_resource_manager *man;
+	unsigned int mem_type;
+	long sofar = 0;
+	long lret;
+
+	for (mem_type = XE_PL_SYSTEM; mem_type <= XE_PL_TT; ++mem_type) {
+		man = ttm_manager_type(&xe->ttm, mem_type);
+		if (!man || !man->use_tt)
+			continue;
+
+		lret = xe_ttm_lru_walk_for_evict(&shrink_walk->walk,
+						 &xe->ttm, man,
+						 mem_type, target);
+		if (lret < 0)
+			return lret;
+
+		sofar += lret;
+		if (sofar >= target)
+			break;
+	}
+
+	return sofar;
+}
+
+static unsigned long
+xe_shrinker_count(struct shrinker *shrink, struct shrink_control *sc)
+{
+	struct xe_shrinker *shrinker = to_xe_shrinker(shrink);
+	unsigned long num_pages;
+
+	num_pages = get_nr_swap_pages();
+	read_lock(&shrinker->lock);
+	num_pages = min_t(unsigned long, num_pages, shrinker->shrinkable_pages);
+	num_pages += shrinker->purgeable_pages;
+	read_unlock(&shrinker->lock);
+
+	return num_pages ? num_pages : SHRINK_EMPTY;
+}
+
+static const struct xe_ttm_lru_walk_ops xe_shrink_ops = {
+	.process_bo = xe_bo_shrinker_process,
+	.allow_bo = xe_shrinker_allow_bo,
+};
+
+static unsigned long xe_shrinker_scan(struct shrinker *shrink, struct shrink_control *sc)
+{
+	struct xe_shrinker *shrinker = to_xe_shrinker(shrink);
+	bool is_kswapd = current_is_kswapd();
+	struct ttm_operation_ctx ctx = {
+		.interruptible = false,
+		.no_wait_gpu = !is_kswapd,
+	};
+	unsigned long nr_to_scan, freed = 0;
+	struct xe_shrink_lru_walk shrink_walk = {
+		.walk = {
+			.ops = &xe_shrink_ops,
+			.ctx = &ctx,
+		},
+		.xe = shrinker->xe,
+		.purge = true,
+	};
+	bool purgeable;
+	long ret;
+
+	sc->nr_scanned = 0;
+	nr_to_scan = sc->nr_to_scan;
+
+	read_lock(&shrinker->lock);
+	purgeable = !!shrinker->purgeable_pages;
+	read_unlock(&shrinker->lock);
+
+	while (purgeable && freed < nr_to_scan) {
+		ret = xe_shrinker_walk(&shrink_walk, nr_to_scan);
+		if (ret <= 0)
+			break;
+
+		freed += ret;
+	}
+
+	sc->nr_scanned = freed;
+	if (freed < nr_to_scan)
+		nr_to_scan -= freed;
+	else
+		nr_to_scan = 0;
+	if (!nr_to_scan)
+		return freed ? freed : SHRINK_STOP;
+
+	shrink_walk.purge = false;
+	while (freed < nr_to_scan) {
+		ret = xe_shrinker_walk(&shrink_walk, nr_to_scan);
+		if (ret <= 0)
+			break;
+
+		freed += ret;
+	}
+
+	sc->nr_scanned = freed;
+
+	return freed ? freed : SHRINK_STOP;
+}
+
+/**
+ * xe_shrinker_create() - Create an xe per-device shrinker
+ * @xe: Pointer to the xe device.
+ *
+ * Returns: A pointer to the created shrinker on success,
+ * Negative error code on failure.
+ */
+struct xe_shrinker *xe_shrinker_create(struct xe_device *xe)
+{
+	struct xe_shrinker *shrinker = kzalloc(sizeof(*shrinker), GFP_KERNEL);
+
+	if (!shrinker)
+		return ERR_PTR(-ENOMEM);
+
+	shrinker->shrink = shrinker_alloc(0, "xe system shrinker");
+	if (!shrinker->shrink) {
+		kfree(shrinker);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	shrinker->xe = xe;
+	rwlock_init(&shrinker->lock);
+	shrinker->shrink->count_objects = xe_shrinker_count;
+	shrinker->shrink->scan_objects = xe_shrinker_scan;
+	shrinker->shrink->private_data = shrinker;
+	shrinker_register(shrinker->shrink);
+
+	return shrinker;
+}
+
+/**
+ * xe_shrinker_destroy() - Destroy an xe per-device shrinker
+ * @shrinker: Pointer to the shrinker to destroy.
+ */
+void xe_shrinker_destroy(struct xe_shrinker *shrinker)
+{
+	xe_assert(shrinker->xe, !shrinker->shrinkable_pages);
+	xe_assert(shrinker->xe, !shrinker->purgeable_pages);
+	shrinker_free(shrinker->shrink);
+	kfree(shrinker);
+}
diff --git a/drivers/gpu/drm/xe/xe_shrinker.h b/drivers/gpu/drm/xe/xe_shrinker.h
new file mode 100644
index 000000000000..28a038f4fcbf
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_shrinker.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#ifndef _XE_SHRINKER_H_
+#define _XE_SHRINKER_H_
+
+struct xe_shrinker;
+struct xe_device;
+
+void xe_shrinker_mod_pages(struct xe_shrinker *shrinker, long shrinkable, long purgeable);
+
+struct xe_shrinker *xe_shrinker_create(struct xe_device *xe);
+
+void xe_shrinker_destroy(struct xe_shrinker *shrinker);
+
+#endif
diff --git a/drivers/gpu/drm/xe/xe_ttm_helpers.c b/drivers/gpu/drm/xe/xe_ttm_helpers.c
index 7b08bfd912c8..62d346e229bf 100644
--- a/drivers/gpu/drm/xe/xe_ttm_helpers.c
+++ b/drivers/gpu/drm/xe/xe_ttm_helpers.c
@@ -9,6 +9,80 @@
 
 #include <drm/ttm/ttm_bo.h>
 #include <drm/ttm/ttm_device.h>
+#include <drm/ttm/ttm_placement.h>
+#include <drm/ttm/ttm_tt.h>
+
+/**
+ * xe_ttm_bo_try_shrink - LRU walk helper to shrink a ttm buffer object.
+ * @walk: The struct xe_ttm_lru_walk that describes the walk.
+ * @bo: The buffer object.
+ * @purge: Whether to attempt to purge the bo content since it's no
+ * longer needed.
+ *
+ * The function uses the ttm_tt_back_up functionality to back up or
+ * purge a struct ttm_tt. If the bo is not in system, it's first
+ * moved there.
+ *
+ * Return: The number of pages shrunken or purged, or
+ * negative error code on failure.
+ */
+long xe_ttm_bo_try_shrink(struct xe_ttm_lru_walk *walk, struct ttm_buffer_object *bo,
+			  bool purge)
+{
+	static const struct ttm_place sys_placement_flags = {
+		.fpfn = 0,
+		.lpfn = 0,
+		.mem_type = TTM_PL_SYSTEM,
+		.flags = 0,
+	};
+	static struct ttm_placement sys_placement = {
+		.num_placement = 1,
+		.placement = &sys_placement_flags,
+	};
+	struct ttm_operation_ctx *ctx = walk->ctx;
+	struct ttm_tt *tt = bo->ttm;
+	long lret;
+
+	dma_resv_assert_held(bo->base.resv);
+
+	if (tt || !ttm_tt_is_populated(tt))
+		return 0;
+
+	if (bo->resource->mem_type != TTM_PL_SYSTEM) {
+		int ret = ttm_bo_validate(bo, &sys_placement, ctx);
+
+		if (ret) {
+			if (ret == -EINTR || ret == -EDEADLK ||
+			    ret == -ERESTARTSYS)
+				return ret;
+			return 0;
+		}
+	}
+
+	if (ctx->no_wait_gpu &&
+	    !dma_resv_test_signaled(bo->base.resv,
+				    DMA_RESV_USAGE_BOOKKEEP))
+		return 0;
+
+	lret = dma_resv_wait_timeout(bo->base.resv,
+				     DMA_RESV_USAGE_BOOKKEEP,
+				     walk->ctx->interruptible,
+				     MAX_SCHEDULE_TIMEOUT);
+	if (lret < 0) {
+		if (lret == -ERESTARTSYS)
+			return lret;
+		return 0;
+	}
+
+	if (bo->deleted)
+		lret = ttm_tt_back_up(bo->bdev, tt, true);
+	else
+		lret = ttm_tt_back_up(bo->bdev, tt, purge);
+	if (lret < 0 && lret != -EINTR)
+		return 0;
+
+	return lret;
+}
 
 static bool xe_ttm_lru_walk_trylock(struct xe_ttm_lru_walk *walk,
 				    struct ttm_buffer_object *bo,
diff --git a/drivers/gpu/drm/xe/xe_ttm_helpers.h b/drivers/gpu/drm/xe/xe_ttm_helpers.h
index a52887ce0241..9f626599df9a 100644
--- a/drivers/gpu/drm/xe/xe_ttm_helpers.h
+++ b/drivers/gpu/drm/xe/xe_ttm_helpers.h
@@ -54,6 +54,9 @@ struct xe_ttm_lru_walk {
 	struct drm_exec *exec;
 };
 
+long xe_ttm_bo_try_shrink(struct xe_ttm_lru_walk *walk, struct ttm_buffer_object *bo,
+			  bool purge);
+
 long xe_ttm_lru_walk_for_evict(struct xe_ttm_lru_walk *walk, struct ttm_device *bdev,
 			       struct ttm_resource_manager *man, unsigned int mem_type,
 			       long target);
-- 
2.44.0

Re: [RFC PATCH 0/8] TTM shrinker helpers and xe buffer object shrinker

[Somalapuram, Amaranath]

On 3/29/2024 8:26 PM, Thomas Hellström wrote:
> This series implements TTM shrinker / eviction helpers and an xe bo
> shrinker. It builds on two previous series. First
>
> https://www.mail-archive.com/dri-devel@lists.freedesktop.org/msg484425.html
>
> for patch 1-4, which IMO still could be reviewed and pushed as a
> separate series.
>
> Second the previous TTM shrinker series 
On the latest drm-misc good amount of conflicts on both patch series, 
able to re-base first one, Second on has 16 patches.
If you have latest re-base patches, Please share it.

Regards,
S.Amarnath
> https://lore.kernel.org/linux-mm/b7491378-defd-4f1c-31e2-29e4c77e2d67@amd.com/T/
>
> Where the comment about layering
> https://lore.kernel.org/linux-mm/b7491378-defd-4f1c-31e2-29e4c77e2d67@amd.com/T/#ma918844aa8a6efe8768fdcda0c6590d5c93850c9
>
> now addressed, and this version also implements shmem objects for backup
> rather than direct swap-cache insertions, which was used in the previuos
> series. It turns out that with per-page backup / shrinking, shmem objects
> appears to work just as well as direct swap-cache insertions with the
> added benefit that was introduced in the previous TTM shrinker series to
> avoid running out of swap entries isn't really needed.
>
> In any case, patch 1-4 are better described in their separate series.
> (RFC is removed for those).
>
> Patch 5 could in theory be skipped but introduces a possibility to easily
> add or test multiple backup backends, like the direct swap-cache
> insertion or even files into fast dedicated nvme storage for for example.
>
> Patch 6 introduces helpers in the ttm_pool code for page-by-page shrinking
> and recovery. It avoids having to temporarily allocate a huge amount of
> memory to be able to shrink a buffer object. It also introduces the
> possibility to immediately write-back pages if needed, since that tends
> to be a bit delayed when left to kswapd.
>
> Patch 7 introduces a LRU walk helper for eviction and shrinking. It's
> currently xe-only but not xe-specific and can easily be moved to TTM when
> used by more than one driver or when eviction is implemented using it.
>
> Patch 8 introduces a helper callback for shrinking (Also ready to be
> moved to TTM) and an xe-specific shrinker implementation.
>
> Testing:
> ATM I don't think we have good tests to cover the shrinking functionality
> The series has been tested with a hack that continously creates
> TTM_TT buffer objects until system memory and swap space is exhausted,
> and then reads them back and frees them. However, these tests
> seem to be very slow.
> Ideally a similar test on a machine with very fast solid state or
> similar storage should be set up. Ideally also verifying content
> preservation.
>
> Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
> Cc: Christian König <christian.koenig@amd.com>
> Cc: <dri-devel@lists.freedesktop.org>
>
> Thomas Hellström (8):
>    drm/ttm: Allow TTM LRU list nodes of different types
>    drm/ttm: Use LRU hitches
>    drm/ttm, drm/amdgpu, drm/xe: Consider hitch moves within bulk sublist
>      moves
>    drm/ttm: Allow continued swapout after -ENOSPC falure
>    drm/ttm: Add a virtual base class for graphics memory backup
>    drm/ttm/pool: Provide a helper to shrink pages.
>    drm/xe, drm/ttm: Provide a generic LRU walker helper
>    drm/xe: Add a shrinker for xe bos
>
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c |   4 +
>   drivers/gpu/drm/ttm/Makefile           |   2 +-
>   drivers/gpu/drm/ttm/ttm_backup_shmem.c | 137 +++++++++
>   drivers/gpu/drm/ttm/ttm_bo.c           |   1 +
>   drivers/gpu/drm/ttm/ttm_device.c       |  33 ++-
>   drivers/gpu/drm/ttm/ttm_pool.c         | 391 ++++++++++++++++++++++++-
>   drivers/gpu/drm/ttm/ttm_resource.c     | 231 ++++++++++++---
>   drivers/gpu/drm/ttm/ttm_tt.c           |  34 +++
>   drivers/gpu/drm/xe/Makefile            |   2 +
>   drivers/gpu/drm/xe/xe_bo.c             | 123 ++++++--
>   drivers/gpu/drm/xe/xe_bo.h             |   3 +
>   drivers/gpu/drm/xe/xe_device.c         |   8 +
>   drivers/gpu/drm/xe/xe_device_types.h   |   2 +
>   drivers/gpu/drm/xe/xe_shrinker.c       | 237 +++++++++++++++
>   drivers/gpu/drm/xe/xe_shrinker.h       |  18 ++
>   drivers/gpu/drm/xe/xe_ttm_helpers.c    | 224 ++++++++++++++
>   drivers/gpu/drm/xe/xe_ttm_helpers.h    |  63 ++++
>   drivers/gpu/drm/xe/xe_vm.c             |   4 +
>   include/drm/ttm/ttm_backup.h           | 136 +++++++++
>   include/drm/ttm/ttm_device.h           |   2 +
>   include/drm/ttm/ttm_pool.h             |   4 +
>   include/drm/ttm/ttm_resource.h         |  96 +++++-
>   include/drm/ttm/ttm_tt.h               |  19 ++
>   23 files changed, 1683 insertions(+), 91 deletions(-)
>   create mode 100644 drivers/gpu/drm/ttm/ttm_backup_shmem.c
>   create mode 100644 drivers/gpu/drm/xe/xe_shrinker.c
>   create mode 100644 drivers/gpu/drm/xe/xe_shrinker.h
>   create mode 100644 drivers/gpu/drm/xe/xe_ttm_helpers.c
>   create mode 100644 drivers/gpu/drm/xe/xe_ttm_helpers.h
>   create mode 100644 include/drm/ttm/ttm_backup.h
>

Re: [PATCH 1/8] drm/ttm: Allow TTM LRU list nodes of different types

[Christian König]

Am 29.03.24 um 15:57 schrieb Thomas Hellström:
> To be able to handle list unlocking while traversing the LRU
> list, we want the iterators not only to point to the next
> position of the list traversal, but to insert themselves as
> list nodes at that point to work around the fact that the
> next node might otherwise disappear from the list while
> the iterator is pointing to it.
>
> These list nodes need to be easily distinguishable from other
> list nodes so that others traversing the list can skip
> over them.
>
> So declare a struct ttm_lru_item, with a struct list_head member
> and a type enum. This will slightly increase the size of a
> struct ttm_resource.
>
> v2:
> - Update enum ttm_lru_item_type documentation.
>
> Cc: Christian König <christian.koenig@amd.com>
> Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
> Cc: <dri-devel@lists.freedesktop.org>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>   drivers/gpu/drm/ttm/ttm_device.c   | 13 ++++--
>   drivers/gpu/drm/ttm/ttm_resource.c | 70 ++++++++++++++++++++++--------
>   include/drm/ttm/ttm_resource.h     | 51 +++++++++++++++++++++-
>   3 files changed, 110 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
> index 76027960054f..f27406e851e5 100644
> --- a/drivers/gpu/drm/ttm/ttm_device.c
> +++ b/drivers/gpu/drm/ttm/ttm_device.c
> @@ -270,17 +270,22 @@ EXPORT_SYMBOL(ttm_device_fini);
>   static void ttm_device_clear_lru_dma_mappings(struct ttm_device *bdev,
>   					      struct list_head *list)
>   {
> -	struct ttm_resource *res;
> +	struct ttm_lru_item *lru;
>   
>   	spin_lock(&bdev->lru_lock);
> -	while ((res = list_first_entry_or_null(list, typeof(*res), lru))) {
> -		struct ttm_buffer_object *bo = res->bo;
> +	while ((lru = list_first_entry_or_null(list, typeof(*lru), link))) {
> +		struct ttm_buffer_object *bo;
> +
> +		if (!ttm_lru_item_is_res(lru))
> +			continue;

We should probably define some ttm_lru_for_each_res() and 
ttm_lru_for_each_res_safe() to iterate over the LRU and abstract the 
whole thing much better.



> +
> +		bo = ttm_lru_item_to_res(lru)->bo;
>   
>   		/* Take ref against racing releases once lru_lock is unlocked */
>   		if (!ttm_bo_get_unless_zero(bo))
>   			continue;
>   
> -		list_del_init(&res->lru);
> +		list_del_init(&bo->resource->lru.link);
>   		spin_unlock(&bdev->lru_lock);
>   
>   		if (bo->ttm)
> diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
> index be8d286513f9..7aa5ca5c0e33 100644
> --- a/drivers/gpu/drm/ttm/ttm_resource.c
> +++ b/drivers/gpu/drm/ttm/ttm_resource.c
> @@ -69,8 +69,8 @@ void ttm_lru_bulk_move_tail(struct ttm_lru_bulk_move *bulk)
>   			dma_resv_assert_held(pos->last->bo->base.resv);
>   
>   			man = ttm_manager_type(pos->first->bo->bdev, i);
> -			list_bulk_move_tail(&man->lru[j], &pos->first->lru,
> -					    &pos->last->lru);
> +			list_bulk_move_tail(&man->lru[j], &pos->first->lru.link,
> +					    &pos->last->lru.link);
>   		}
>   	}
>   }
> @@ -83,14 +83,38 @@ ttm_lru_bulk_move_pos(struct ttm_lru_bulk_move *bulk, struct ttm_resource *res)
>   	return &bulk->pos[res->mem_type][res->bo->priority];
>   }
>   
> +/* Return the previous resource on the list (skip over non-resource list items) */
> +static struct ttm_resource *ttm_lru_prev_res(struct ttm_resource *cur)
> +{
> +	struct ttm_lru_item *lru = &cur->lru;
> +
> +	do {
> +		lru = list_prev_entry(lru, link);
> +	} while (!ttm_lru_item_is_res(lru));
> +
> +	return ttm_lru_item_to_res(lru);
> +}
> +
> +/* Return the next resource on the list (skip over non-resource list items) */
> +static struct ttm_resource *ttm_lru_next_res(struct ttm_resource *cur)
> +{
> +	struct ttm_lru_item *lru = &cur->lru;
> +
> +	do {
> +		lru = list_next_entry(lru, link);
> +	} while (!ttm_lru_item_is_res(lru));
> +
> +	return ttm_lru_item_to_res(lru);
> +}
> +
>   /* Move the resource to the tail of the bulk move range */
>   static void ttm_lru_bulk_move_pos_tail(struct ttm_lru_bulk_move_pos *pos,
>   				       struct ttm_resource *res)
>   {
>   	if (pos->last != res) {
>   		if (pos->first == res)
> -			pos->first = list_next_entry(res, lru);
> -		list_move(&res->lru, &pos->last->lru);
> +			pos->first = ttm_lru_next_res(res);
> +		list_move(&res->lru.link, &pos->last->lru.link);
>   		pos->last = res;
>   	}
>   }
> @@ -121,11 +145,11 @@ static void ttm_lru_bulk_move_del(struct ttm_lru_bulk_move *bulk,
>   		pos->first = NULL;
>   		pos->last = NULL;
>   	} else if (pos->first == res) {
> -		pos->first = list_next_entry(res, lru);
> +		pos->first = ttm_lru_next_res(res);
>   	} else if (pos->last == res) {
> -		pos->last = list_prev_entry(res, lru);
> +		pos->last = ttm_lru_prev_res(res);
>   	} else {
> -		list_move(&res->lru, &pos->last->lru);
> +		list_move(&res->lru.link, &pos->last->lru.link);
>   	}
>   }
>   
> @@ -154,7 +178,7 @@ void ttm_resource_move_to_lru_tail(struct ttm_resource *res)
>   	lockdep_assert_held(&bo->bdev->lru_lock);
>   
>   	if (bo->pin_count) {
> -		list_move_tail(&res->lru, &bdev->pinned);
> +		list_move_tail(&res->lru.link, &bdev->pinned);
>   
>   	} else	if (bo->bulk_move) {
>   		struct ttm_lru_bulk_move_pos *pos =
> @@ -165,7 +189,7 @@ void ttm_resource_move_to_lru_tail(struct ttm_resource *res)
>   		struct ttm_resource_manager *man;
>   
>   		man = ttm_manager_type(bdev, res->mem_type);
> -		list_move_tail(&res->lru, &man->lru[bo->priority]);
> +		list_move_tail(&res->lru.link, &man->lru[bo->priority]);
>   	}
>   }
>   
> @@ -196,9 +220,9 @@ void ttm_resource_init(struct ttm_buffer_object *bo,
>   	man = ttm_manager_type(bo->bdev, place->mem_type);
>   	spin_lock(&bo->bdev->lru_lock);
>   	if (bo->pin_count)
> -		list_add_tail(&res->lru, &bo->bdev->pinned);
> +		list_add_tail(&res->lru.link, &bo->bdev->pinned);
>   	else
> -		list_add_tail(&res->lru, &man->lru[bo->priority]);
> +		list_add_tail(&res->lru.link, &man->lru[bo->priority]);
>   	man->usage += res->size;
>   	spin_unlock(&bo->bdev->lru_lock);
>   }
> @@ -220,7 +244,7 @@ void ttm_resource_fini(struct ttm_resource_manager *man,
>   	struct ttm_device *bdev = man->bdev;
>   
>   	spin_lock(&bdev->lru_lock);
> -	list_del_init(&res->lru);
> +	list_del_init(&res->lru.link);
>   	man->usage -= res->size;
>   	spin_unlock(&bdev->lru_lock);
>   }
> @@ -471,14 +495,16 @@ struct ttm_resource *
>   ttm_resource_manager_first(struct ttm_resource_manager *man,
>   			   struct ttm_resource_cursor *cursor)
>   {
> -	struct ttm_resource *res;
> +	struct ttm_lru_item *lru;
>   
>   	lockdep_assert_held(&man->bdev->lru_lock);
>   
>   	for (cursor->priority = 0; cursor->priority < TTM_MAX_BO_PRIORITY;
>   	     ++cursor->priority)
> -		list_for_each_entry(res, &man->lru[cursor->priority], lru)
> -			return res;
> +		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
> +			if (ttm_lru_item_is_res(lru))
> +				return ttm_lru_item_to_res(lru);
> +		}
>   
>   	return NULL;
>   }
> @@ -497,15 +523,21 @@ ttm_resource_manager_next(struct ttm_resource_manager *man,
>   			  struct ttm_resource_cursor *cursor,
>   			  struct ttm_resource *res)
>   {
> +	struct ttm_lru_item *lru = &res->lru;
> +
>   	lockdep_assert_held(&man->bdev->lru_lock);
>   
> -	list_for_each_entry_continue(res, &man->lru[cursor->priority], lru)
> -		return res;
> +	list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
> +		if (ttm_lru_item_is_res(lru))
> +			return ttm_lru_item_to_res(lru);
> +	}
>   
>   	for (++cursor->priority; cursor->priority < TTM_MAX_BO_PRIORITY;
>   	     ++cursor->priority)
> -		list_for_each_entry(res, &man->lru[cursor->priority], lru)
> -			return res;
> +		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
> +			if (ttm_lru_item_is_res(lru))
> +				ttm_lru_item_to_res(lru);
> +		}
>   
>   	return NULL;
>   }
> diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
> index 69769355139f..4babc4ff10b0 100644
> --- a/include/drm/ttm/ttm_resource.h
> +++ b/include/drm/ttm/ttm_resource.h
> @@ -49,6 +49,43 @@ struct io_mapping;
>   struct sg_table;
>   struct scatterlist;
>   
> +/**
> + * enum ttm_lru_item_type - enumerate ttm_lru_item subclasses
> + */
> +enum ttm_lru_item_type {
> +	/** @TTM_LRU_RESOURCE: The resource subclass */
> +	TTM_LRU_RESOURCE,
> +	/** @TTM_LRU_HITCH: The iterator hitch subclass */
> +	TTM_LRU_HITCH

I'm really wondering we we can't use a special value for mem_type for 
the iterator hitch instead.

Regards,
Christian.

> +};
> +
> +/**
> + * struct ttm_lru_item - The TTM lru list node base class
> + * @link: The list link
> + * @type: The subclass type
> + */
> +struct ttm_lru_item {
> +	struct list_head link;
> +	enum ttm_lru_item_type type;
> +};
> +
> +/**
> + * ttm_lru_item_init() - initialize a struct ttm_lru_item
> + * @item: The item to initialize
> + * @type: The subclass type
> + */
> +static inline void ttm_lru_item_init(struct ttm_lru_item *item,
> +				     enum ttm_lru_item_type type)
> +{
> +	item->type = type;
> +	INIT_LIST_HEAD(&item->link);
> +}
> +
> +static inline bool ttm_lru_item_is_res(const struct ttm_lru_item *item)
> +{
> +	return item->type == TTM_LRU_RESOURCE;
> +}
> +
>   struct ttm_resource_manager_func {
>   	/**
>   	 * struct ttm_resource_manager_func member alloc
> @@ -217,9 +254,21 @@ struct ttm_resource {
>   	/**
>   	 * @lru: Least recently used list, see &ttm_resource_manager.lru
>   	 */
> -	struct list_head lru;
> +	struct ttm_lru_item lru;
>   };
>   
> +/**
> + * ttm_lru_item_to_res() - Downcast a struct ttm_lru_item to a struct ttm_resource
> + * @item: The struct ttm_lru_item to downcast
> + *
> + * Return: Pointer to the embedding struct ttm_resource
> + */
> +static inline struct ttm_resource *
> +ttm_lru_item_to_res(struct ttm_lru_item *item)
> +{
> +	return container_of(item, struct ttm_resource, lru);
> +}
> +
>   /**
>    * struct ttm_resource_cursor
>    *

Re: [PATCH 2/8] drm/ttm: Use LRU hitches

[Christian König]

Am 29.03.24 um 15:57 schrieb Thomas Hellström:
> Have iterators insert themselves into the list they are iterating
> over using hitch list nodes. Since only the iterator owner
> can remove these list nodes from the list, it's safe to unlock
> the list and when continuing, use them as a starting point. Due to
> the way LRU bumping works in TTM, newly added items will not be
> missed, and bumped items will be iterated over a second time before
> reaching the end of the list.
>
> The exception is list with bulk move sublists. When bumping a
> sublist, a hitch that is part of that sublist will also be moved
> and we might miss items if restarting from it. This will be
> addressed in a later patch.
>
> v2:
> - Updated ttm_resource_cursor_fini() documentation.
>
> Cc: Christian König <christian.koenig@amd.com>
> Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
> Cc: <dri-devel@lists.freedesktop.org>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>   drivers/gpu/drm/ttm/ttm_bo.c       |  1 +
>   drivers/gpu/drm/ttm/ttm_device.c   |  9 ++-
>   drivers/gpu/drm/ttm/ttm_resource.c | 94 ++++++++++++++++++++----------
>   include/drm/ttm/ttm_resource.h     | 16 +++--
>   4 files changed, 82 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index e059b1e1b13b..b6f75a0ff2e5 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -622,6 +622,7 @@ int ttm_mem_evict_first(struct ttm_device *bdev,
>   		if (locked)
>   			dma_resv_unlock(res->bo->base.resv);
>   	}
> +	ttm_resource_cursor_fini_locked(&cursor);
>   
>   	if (!bo) {
>   		if (busy_bo && !ttm_bo_get_unless_zero(busy_bo))
> diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
> index f27406e851e5..e8a6a1dab669 100644
> --- a/drivers/gpu/drm/ttm/ttm_device.c
> +++ b/drivers/gpu/drm/ttm/ttm_device.c
> @@ -169,12 +169,17 @@ int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
>   			num_pages = PFN_UP(bo->base.size);
>   			ret = ttm_bo_swapout(bo, ctx, gfp_flags);
>   			/* ttm_bo_swapout has dropped the lru_lock */
> -			if (!ret)
> +			if (!ret) {
> +				ttm_resource_cursor_fini(&cursor);
>   				return num_pages;
> -			if (ret != -EBUSY)
> +			}
> +			if (ret != -EBUSY) {
> +				ttm_resource_cursor_fini(&cursor);
>   				return ret;
> +			}
>   		}
>   	}
> +	ttm_resource_cursor_fini_locked(&cursor);
>   	spin_unlock(&bdev->lru_lock);
>   	return 0;
>   }
> diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
> index 7aa5ca5c0e33..ccc31ad85e3b 100644
> --- a/drivers/gpu/drm/ttm/ttm_resource.c
> +++ b/drivers/gpu/drm/ttm/ttm_resource.c
> @@ -32,6 +32,37 @@
>   
>   #include <drm/drm_util.h>
>   
> +/**
> + * ttm_resource_cursor_fini_locked() - Finalize the LRU list cursor usage
> + * @cursor: The struct ttm_resource_cursor to finalize.
> + *
> + * The function pulls the LRU list cursor off any lists it was previusly
> + * attached to. Needs to be called with the LRU lock held. The function
> + * can be called multiple times after eachother.
> + */
> +void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor)
> +{
> +	lockdep_assert_held(&cursor->man->bdev->lru_lock);
> +	list_del_init(&cursor->hitch.link);
> +}
> +
> +/**
> + * ttm_resource_cursor_fini() - Finalize the LRU list cursor usage
> + * @cursor: The struct ttm_resource_cursor to finalize.
> + *
> + * The function pulls the LRU list cursor off any lists it was previusly
> + * attached to. Needs to be called without the LRU list lock held. The
> + * function can be called multiple times after eachother.
> + */
> +void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor)
> +{
> +	spinlock_t *lru_lock = &cursor->man->bdev->lru_lock;
> +
> +	spin_lock(lru_lock);
> +	ttm_resource_cursor_fini_locked(cursor);
> +	spin_unlock(lru_lock);
> +}
> +
>   /**
>    * ttm_lru_bulk_move_init - initialize a bulk move structure
>    * @bulk: the structure to init
> @@ -484,62 +515,63 @@ void ttm_resource_manager_debug(struct ttm_resource_manager *man,
>   EXPORT_SYMBOL(ttm_resource_manager_debug);
>   
>   /**
> - * ttm_resource_manager_first
> - *
> - * @man: resource manager to iterate over
> + * ttm_resource_manager_next() - Continue iterating over the resource manager
> + * resources
>    * @cursor: cursor to record the position
>    *
> - * Returns the first resource from the resource manager.
> + * Return: The next resource from the resource manager.
>    */
>   struct ttm_resource *
> -ttm_resource_manager_first(struct ttm_resource_manager *man,
> -			   struct ttm_resource_cursor *cursor)
> +ttm_resource_manager_next(struct ttm_resource_cursor *cursor)

Why are you switching first/next here? It took me a moment to realize 
that the two functions switched places.

>   {
> +	struct ttm_resource_manager *man = cursor->man;
>   	struct ttm_lru_item *lru;
>   
>   	lockdep_assert_held(&man->bdev->lru_lock);
>   
> -	for (cursor->priority = 0; cursor->priority < TTM_MAX_BO_PRIORITY;
> -	     ++cursor->priority)
> -		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
> -			if (ttm_lru_item_is_res(lru))
> +	do {
> +		lru = &cursor->hitch;
> +		list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
> +			if (ttm_lru_item_is_res(lru)) {
> +				list_move(&cursor->hitch.link, &lru->link);
>   				return ttm_lru_item_to_res(lru);
> +			}
>   		}
>   
> +		if (++cursor->priority >= TTM_MAX_BO_PRIORITY)
> +			break;
> +
> +		list_move(&cursor->hitch.link, &man->lru[cursor->priority]);
> +	} while (true);
> +
> +	list_del_init(&cursor->hitch.link);
> +
>   	return NULL;
>   }
>   
>   /**
> - * ttm_resource_manager_next
> - *
> + * ttm_resource_manager_first() - Start iterating over the resources
> + * of a resource manager
>    * @man: resource manager to iterate over
>    * @cursor: cursor to record the position
> - * @res: the current resource pointer
>    *
> - * Returns the next resource from the resource manager.
> + * Initializes the cursor and starts iterating. When done iterating,
> + * the caller must explicitly call ttm_resource_cursor_fini().
> + *
> + * Return: The first resource from the resource manager.
>    */
>   struct ttm_resource *
> -ttm_resource_manager_next(struct ttm_resource_manager *man,
> -			  struct ttm_resource_cursor *cursor,
> -			  struct ttm_resource *res)
> +ttm_resource_manager_first(struct ttm_resource_manager *man,
> +			   struct ttm_resource_cursor *cursor)
>   {
> -	struct ttm_lru_item *lru = &res->lru;
> -
>   	lockdep_assert_held(&man->bdev->lru_lock);
>   
> -	list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
> -		if (ttm_lru_item_is_res(lru))
> -			return ttm_lru_item_to_res(lru);
> -	}
> +	cursor->priority = 0;
> +	cursor->man = man;
> +	ttm_lru_item_init(&cursor->hitch, TTM_LRU_HITCH);
> +	list_move(&cursor->hitch.link, &man->lru[cursor->priority]);

That should probably be a list_add() instead.

Need to take a closer look what actually changed when the functions keep 
their original order.

Christian.

>   
> -	for (++cursor->priority; cursor->priority < TTM_MAX_BO_PRIORITY;
> -	     ++cursor->priority)
> -		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
> -			if (ttm_lru_item_is_res(lru))
> -				ttm_lru_item_to_res(lru);
> -		}
> -
> -	return NULL;
> +	return ttm_resource_manager_next(cursor);
>   }
>   
>   static void ttm_kmap_iter_iomap_map_local(struct ttm_kmap_iter *iter,
> diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
> index 4babc4ff10b0..dfc01258c981 100644
> --- a/include/drm/ttm/ttm_resource.h
> +++ b/include/drm/ttm/ttm_resource.h
> @@ -271,15 +271,23 @@ ttm_lru_item_to_res(struct ttm_lru_item *item)
>   
>   /**
>    * struct ttm_resource_cursor
> - *
> + * @man: The resource manager currently being iterated over
> + * @hitch: A hitch list node inserted before the next resource
> + * to iterate over.
>    * @priority: the current priority
>    *
>    * Cursor to iterate over the resources in a manager.
>    */
>   struct ttm_resource_cursor {
> +	struct ttm_resource_manager *man;
> +	struct ttm_lru_item hitch;
>   	unsigned int priority;
>   };
>   
> +void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor);
> +
> +void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor);
> +
>   /**
>    * struct ttm_lru_bulk_move_pos
>    *
> @@ -438,9 +446,7 @@ struct ttm_resource *
>   ttm_resource_manager_first(struct ttm_resource_manager *man,
>   			   struct ttm_resource_cursor *cursor);
>   struct ttm_resource *
> -ttm_resource_manager_next(struct ttm_resource_manager *man,
> -			  struct ttm_resource_cursor *cursor,
> -			  struct ttm_resource *res);
> +ttm_resource_manager_next(struct ttm_resource_cursor *cursor);
>   
>   /**
>    * ttm_resource_manager_for_each_res - iterate over all resources
> @@ -452,7 +458,7 @@ ttm_resource_manager_next(struct ttm_resource_manager *man,
>    */
>   #define ttm_resource_manager_for_each_res(man, cursor, res)		\
>   	for (res = ttm_resource_manager_first(man, cursor); res;	\
> -	     res = ttm_resource_manager_next(man, cursor, res))
> +	     res = ttm_resource_manager_next(cursor))
>   
>   struct ttm_kmap_iter *
>   ttm_kmap_iter_iomap_init(struct ttm_kmap_iter_iomap *iter_io,

Re: [PATCH 1/8] drm/ttm: Allow TTM LRU list nodes of different types

[Thomas Hellström]

Hi, Christian.
Thanks for reviewing. 

On Fri, 2024-04-05 at 14:34 +0200, Christian König wrote:
> Am 29.03.24 um 15:57 schrieb Thomas Hellström:
> > To be able to handle list unlocking while traversing the LRU
> > list, we want the iterators not only to point to the next
> > position of the list traversal, but to insert themselves as
> > list nodes at that point to work around the fact that the
> > next node might otherwise disappear from the list while
> > the iterator is pointing to it.
> > 
> > These list nodes need to be easily distinguishable from other
> > list nodes so that others traversing the list can skip
> > over them.
> > 
> > So declare a struct ttm_lru_item, with a struct list_head member
> > and a type enum. This will slightly increase the size of a
> > struct ttm_resource.
> > 
> > v2:
> > - Update enum ttm_lru_item_type documentation.
> > 
> > Cc: Christian König <christian.koenig@amd.com>
> > Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
> > Cc: <dri-devel@lists.freedesktop.org>
> > Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> > ---
> >   drivers/gpu/drm/ttm/ttm_device.c   | 13 ++++--
> >   drivers/gpu/drm/ttm/ttm_resource.c | 70 ++++++++++++++++++++++---
> > -----
> >   include/drm/ttm/ttm_resource.h     | 51 +++++++++++++++++++++-
> >   3 files changed, 110 insertions(+), 24 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/ttm/ttm_device.c
> > b/drivers/gpu/drm/ttm/ttm_device.c
> > index 76027960054f..f27406e851e5 100644
> > --- a/drivers/gpu/drm/ttm/ttm_device.c
> > +++ b/drivers/gpu/drm/ttm/ttm_device.c
> > @@ -270,17 +270,22 @@ EXPORT_SYMBOL(ttm_device_fini);
> >   static void ttm_device_clear_lru_dma_mappings(struct ttm_device
> > *bdev,
> >   					      struct list_head
> > *list)
> >   {
> > -	struct ttm_resource *res;
> > +	struct ttm_lru_item *lru;
> >   
> >   	spin_lock(&bdev->lru_lock);
> > -	while ((res = list_first_entry_or_null(list, typeof(*res),
> > lru))) {
> > -		struct ttm_buffer_object *bo = res->bo;
> > +	while ((lru = list_first_entry_or_null(list, typeof(*lru),
> > link))) {
> > +		struct ttm_buffer_object *bo;
> > +
> > +		if (!ttm_lru_item_is_res(lru))
> > +			continue;
> 
> We should probably define some ttm_lru_for_each_res() and 
> ttm_lru_for_each_res_safe() to iterate over the LRU and abstract the 
> whole thing much better.

We actually have that already, ttm_resource_manager_for_each_res(), and
later in the series a more elaborate lru list walker that also takes
the object lock based on how the struct ttm_operation_context is set
up. (xe_ttm_lru_walk_for_evict())

At this stage, unless done like above, the list traversal isn't safe
against unlocking the lru list, so any change here IMO needs to be done
as a follow up patch.

> 
> 
> 
> > +
> > +		bo = ttm_lru_item_to_res(lru)->bo;
> >   
> >   		/* Take ref against racing releases once lru_lock
> > is unlocked */
> >   		if (!ttm_bo_get_unless_zero(bo))
> >   			continue;
> >   
> > -		list_del_init(&res->lru);
> > +		list_del_init(&bo->resource->lru.link);
> >   		spin_unlock(&bdev->lru_lock);
> >   
> >   		if (bo->ttm)
> > diff --git a/drivers/gpu/drm/ttm/ttm_resource.c
> > b/drivers/gpu/drm/ttm/ttm_resource.c
> > index be8d286513f9..7aa5ca5c0e33 100644
> > --- a/drivers/gpu/drm/ttm/ttm_resource.c
> > +++ b/drivers/gpu/drm/ttm/ttm_resource.c
> > @@ -69,8 +69,8 @@ void ttm_lru_bulk_move_tail(struct
> > ttm_lru_bulk_move *bulk)
> >   			dma_resv_assert_held(pos->last->bo-
> > >base.resv);
> >   
> >   			man = ttm_manager_type(pos->first->bo-
> > >bdev, i);
> > -			list_bulk_move_tail(&man->lru[j], &pos-
> > >first->lru,
> > -					    &pos->last->lru);
> > +			list_bulk_move_tail(&man->lru[j], &pos-
> > >first->lru.link,
> > +					    &pos->last->lru.link);
> >   		}
> >   	}
> >   }
> > @@ -83,14 +83,38 @@ ttm_lru_bulk_move_pos(struct ttm_lru_bulk_move
> > *bulk, struct ttm_resource *res)
> >   	return &bulk->pos[res->mem_type][res->bo->priority];
> >   }
> >   
> > +/* Return the previous resource on the list (skip over non-
> > resource list items) */
> > +static struct ttm_resource *ttm_lru_prev_res(struct ttm_resource
> > *cur)
> > +{
> > +	struct ttm_lru_item *lru = &cur->lru;
> > +
> > +	do {
> > +		lru = list_prev_entry(lru, link);
> > +	} while (!ttm_lru_item_is_res(lru));
> > +
> > +	return ttm_lru_item_to_res(lru);
> > +}
> > +
> > +/* Return the next resource on the list (skip over non-resource
> > list items) */
> > +static struct ttm_resource *ttm_lru_next_res(struct ttm_resource
> > *cur)
> > +{
> > +	struct ttm_lru_item *lru = &cur->lru;
> > +
> > +	do {
> > +		lru = list_next_entry(lru, link);
> > +	} while (!ttm_lru_item_is_res(lru));
> > +
> > +	return ttm_lru_item_to_res(lru);
> > +}
> > +
> >   /* Move the resource to the tail of the bulk move range */
> >   static void ttm_lru_bulk_move_pos_tail(struct
> > ttm_lru_bulk_move_pos *pos,
> >   				       struct ttm_resource *res)
> >   {
> >   	if (pos->last != res) {
> >   		if (pos->first == res)
> > -			pos->first = list_next_entry(res, lru);
> > -		list_move(&res->lru, &pos->last->lru);
> > +			pos->first = ttm_lru_next_res(res);
> > +		list_move(&res->lru.link, &pos->last->lru.link);
> >   		pos->last = res;
> >   	}
> >   }
> > @@ -121,11 +145,11 @@ static void ttm_lru_bulk_move_del(struct
> > ttm_lru_bulk_move *bulk,
> >   		pos->first = NULL;
> >   		pos->last = NULL;
> >   	} else if (pos->first == res) {
> > -		pos->first = list_next_entry(res, lru);
> > +		pos->first = ttm_lru_next_res(res);
> >   	} else if (pos->last == res) {
> > -		pos->last = list_prev_entry(res, lru);
> > +		pos->last = ttm_lru_prev_res(res);
> >   	} else {
> > -		list_move(&res->lru, &pos->last->lru);
> > +		list_move(&res->lru.link, &pos->last->lru.link);
> >   	}
> >   }
> >   
> > @@ -154,7 +178,7 @@ void ttm_resource_move_to_lru_tail(struct
> > ttm_resource *res)
> >   	lockdep_assert_held(&bo->bdev->lru_lock);
> >   
> >   	if (bo->pin_count) {
> > -		list_move_tail(&res->lru, &bdev->pinned);
> > +		list_move_tail(&res->lru.link, &bdev->pinned);
> >   
> >   	} else	if (bo->bulk_move) {
> >   		struct ttm_lru_bulk_move_pos *pos =
> > @@ -165,7 +189,7 @@ void ttm_resource_move_to_lru_tail(struct
> > ttm_resource *res)
> >   		struct ttm_resource_manager *man;
> >   
> >   		man = ttm_manager_type(bdev, res->mem_type);
> > -		list_move_tail(&res->lru, &man->lru[bo-
> > >priority]);
> > +		list_move_tail(&res->lru.link, &man->lru[bo-
> > >priority]);
> >   	}
> >   }
> >   
> > @@ -196,9 +220,9 @@ void ttm_resource_init(struct ttm_buffer_object
> > *bo,
> >   	man = ttm_manager_type(bo->bdev, place->mem_type);
> >   	spin_lock(&bo->bdev->lru_lock);
> >   	if (bo->pin_count)
> > -		list_add_tail(&res->lru, &bo->bdev->pinned);
> > +		list_add_tail(&res->lru.link, &bo->bdev->pinned);
> >   	else
> > -		list_add_tail(&res->lru, &man->lru[bo->priority]);
> > +		list_add_tail(&res->lru.link, &man->lru[bo-
> > >priority]);
> >   	man->usage += res->size;
> >   	spin_unlock(&bo->bdev->lru_lock);
> >   }
> > @@ -220,7 +244,7 @@ void ttm_resource_fini(struct
> > ttm_resource_manager *man,
> >   	struct ttm_device *bdev = man->bdev;
> >   
> >   	spin_lock(&bdev->lru_lock);
> > -	list_del_init(&res->lru);
> > +	list_del_init(&res->lru.link);
> >   	man->usage -= res->size;
> >   	spin_unlock(&bdev->lru_lock);
> >   }
> > @@ -471,14 +495,16 @@ struct ttm_resource *
> >   ttm_resource_manager_first(struct ttm_resource_manager *man,
> >   			   struct ttm_resource_cursor *cursor)
> >   {
> > -	struct ttm_resource *res;
> > +	struct ttm_lru_item *lru;
> >   
> >   	lockdep_assert_held(&man->bdev->lru_lock);
> >   
> >   	for (cursor->priority = 0; cursor->priority <
> > TTM_MAX_BO_PRIORITY;
> >   	     ++cursor->priority)
> > -		list_for_each_entry(res, &man->lru[cursor-
> > >priority], lru)
> > -			return res;
> > +		list_for_each_entry(lru, &man->lru[cursor-
> > >priority], link) {
> > +			if (ttm_lru_item_is_res(lru))
> > +				return ttm_lru_item_to_res(lru);
> > +		}
> >   
> >   	return NULL;
> >   }
> > @@ -497,15 +523,21 @@ ttm_resource_manager_next(struct
> > ttm_resource_manager *man,
> >   			  struct ttm_resource_cursor *cursor,
> >   			  struct ttm_resource *res)
> >   {
> > +	struct ttm_lru_item *lru = &res->lru;
> > +
> >   	lockdep_assert_held(&man->bdev->lru_lock);
> >   
> > -	list_for_each_entry_continue(res, &man->lru[cursor-
> > >priority], lru)
> > -		return res;
> > +	list_for_each_entry_continue(lru, &man->lru[cursor-
> > >priority], link) {
> > +		if (ttm_lru_item_is_res(lru))
> > +			return ttm_lru_item_to_res(lru);
> > +	}
> >   
> >   	for (++cursor->priority; cursor->priority <
> > TTM_MAX_BO_PRIORITY;
> >   	     ++cursor->priority)
> > -		list_for_each_entry(res, &man->lru[cursor-
> > >priority], lru)
> > -			return res;
> > +		list_for_each_entry(lru, &man->lru[cursor-
> > >priority], link) {
> > +			if (ttm_lru_item_is_res(lru))
> > +				ttm_lru_item_to_res(lru);
> > +		}
> >   
> >   	return NULL;
> >   }
> > diff --git a/include/drm/ttm/ttm_resource.h
> > b/include/drm/ttm/ttm_resource.h
> > index 69769355139f..4babc4ff10b0 100644
> > --- a/include/drm/ttm/ttm_resource.h
> > +++ b/include/drm/ttm/ttm_resource.h
> > @@ -49,6 +49,43 @@ struct io_mapping;
> >   struct sg_table;
> >   struct scatterlist;
> >   
> > +/**
> > + * enum ttm_lru_item_type - enumerate ttm_lru_item subclasses
> > + */
> > +enum ttm_lru_item_type {
> > +	/** @TTM_LRU_RESOURCE: The resource subclass */
> > +	TTM_LRU_RESOURCE,
> > +	/** @TTM_LRU_HITCH: The iterator hitch subclass */
> > +	TTM_LRU_HITCH
> 
> I'm really wondering we we can't use a special value for mem_type for
> the iterator hitch instead.

We can use a special TTM resource. I was thinking back and forth about
this for the initial series. But landed on this solution for two
reasons:

1) Code separation: I think we want to make the lru traversal self-
contained if possible. (Thinking forward about Oak's work on splitting
out the TTM LRU traversal) and future possible merging with the drm gem
LRU traversal.

2) Maintainability. If we (ab)use the ttm resources as hitches, this
might be confusing to people reading the code.

I don't have a very strong opinion on this, though. If you think
otherwise we can embed a struct ttm_resource in the cursor.

/Thomas
 


> 
> Regards,
> Christian.
> 
> > +};
> > +
> > +/**
> > + * struct ttm_lru_item - The TTM lru list node base class
> > + * @link: The list link
> > + * @type: The subclass type
> > + */
> > +struct ttm_lru_item {
> > +	struct list_head link;
> > +	enum ttm_lru_item_type type;
> > +};
> > +
> > +/**
> > + * ttm_lru_item_init() - initialize a struct ttm_lru_item
> > + * @item: The item to initialize
> > + * @type: The subclass type
> > + */
> > +static inline void ttm_lru_item_init(struct ttm_lru_item *item,
> > +				     enum ttm_lru_item_type type)
> > +{
> > +	item->type = type;
> > +	INIT_LIST_HEAD(&item->link);
> > +}
> > +
> > +static inline bool ttm_lru_item_is_res(const struct ttm_lru_item
> > *item)
> > +{
> > +	return item->type == TTM_LRU_RESOURCE;
> > +}
> > +
> >   struct ttm_resource_manager_func {
> >   	/**
> >   	 * struct ttm_resource_manager_func member alloc
> > @@ -217,9 +254,21 @@ struct ttm_resource {
> >   	/**
> >   	 * @lru: Least recently used list, see
> > &ttm_resource_manager.lru
> >   	 */
> > -	struct list_head lru;
> > +	struct ttm_lru_item lru;
> >   };
> >   
> > +/**
> > + * ttm_lru_item_to_res() - Downcast a struct ttm_lru_item to a
> > struct ttm_resource
> > + * @item: The struct ttm_lru_item to downcast
> > + *
> > + * Return: Pointer to the embedding struct ttm_resource
> > + */
> > +static inline struct ttm_resource *
> > +ttm_lru_item_to_res(struct ttm_lru_item *item)
> > +{
> > +	return container_of(item, struct ttm_resource, lru);
> > +}
> > +
> >   /**
> >    * struct ttm_resource_cursor
> >    *
> 

Re: [PATCH 2/8] drm/ttm: Use LRU hitches

[Thomas Hellström]

On Fri, 2024-04-05 at 14:41 +0200, Christian König wrote:
> Am 29.03.24 um 15:57 schrieb Thomas Hellström:
> > Have iterators insert themselves into the list they are iterating
> > over using hitch list nodes. Since only the iterator owner
> > can remove these list nodes from the list, it's safe to unlock
> > the list and when continuing, use them as a starting point. Due to
> > the way LRU bumping works in TTM, newly added items will not be
> > missed, and bumped items will be iterated over a second time before
> > reaching the end of the list.
> > 
> > The exception is list with bulk move sublists. When bumping a
> > sublist, a hitch that is part of that sublist will also be moved
> > and we might miss items if restarting from it. This will be
> > addressed in a later patch.
> > 
> > v2:
> > - Updated ttm_resource_cursor_fini() documentation.
> > 
> > Cc: Christian König <christian.koenig@amd.com>
> > Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
> > Cc: <dri-devel@lists.freedesktop.org>
> > Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> > ---
> >   drivers/gpu/drm/ttm/ttm_bo.c       |  1 +
> >   drivers/gpu/drm/ttm/ttm_device.c   |  9 ++-
> >   drivers/gpu/drm/ttm/ttm_resource.c | 94 ++++++++++++++++++++-----
> > -----
> >   include/drm/ttm/ttm_resource.h     | 16 +++--
> >   4 files changed, 82 insertions(+), 38 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c
> > b/drivers/gpu/drm/ttm/ttm_bo.c
> > index e059b1e1b13b..b6f75a0ff2e5 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> > @@ -622,6 +622,7 @@ int ttm_mem_evict_first(struct ttm_device
> > *bdev,
> >   		if (locked)
> >   			dma_resv_unlock(res->bo->base.resv);
> >   	}
> > +	ttm_resource_cursor_fini_locked(&cursor);
> >   
> >   	if (!bo) {
> >   		if (busy_bo && !ttm_bo_get_unless_zero(busy_bo))
> > diff --git a/drivers/gpu/drm/ttm/ttm_device.c
> > b/drivers/gpu/drm/ttm/ttm_device.c
> > index f27406e851e5..e8a6a1dab669 100644
> > --- a/drivers/gpu/drm/ttm/ttm_device.c
> > +++ b/drivers/gpu/drm/ttm/ttm_device.c
> > @@ -169,12 +169,17 @@ int ttm_device_swapout(struct ttm_device
> > *bdev, struct ttm_operation_ctx *ctx,
> >   			num_pages = PFN_UP(bo->base.size);
> >   			ret = ttm_bo_swapout(bo, ctx, gfp_flags);
> >   			/* ttm_bo_swapout has dropped the lru_lock
> > */
> > -			if (!ret)
> > +			if (!ret) {
> > +				ttm_resource_cursor_fini(&cursor);
> >   				return num_pages;
> > -			if (ret != -EBUSY)
> > +			}
> > +			if (ret != -EBUSY) {
> > +				ttm_resource_cursor_fini(&cursor);
> >   				return ret;
> > +			}
> >   		}
> >   	}
> > +	ttm_resource_cursor_fini_locked(&cursor);
> >   	spin_unlock(&bdev->lru_lock);
> >   	return 0;
> >   }
> > diff --git a/drivers/gpu/drm/ttm/ttm_resource.c
> > b/drivers/gpu/drm/ttm/ttm_resource.c
> > index 7aa5ca5c0e33..ccc31ad85e3b 100644
> > --- a/drivers/gpu/drm/ttm/ttm_resource.c
> > +++ b/drivers/gpu/drm/ttm/ttm_resource.c
> > @@ -32,6 +32,37 @@
> >   
> >   #include <drm/drm_util.h>
> >   
> > +/**
> > + * ttm_resource_cursor_fini_locked() - Finalize the LRU list
> > cursor usage
> > + * @cursor: The struct ttm_resource_cursor to finalize.
> > + *
> > + * The function pulls the LRU list cursor off any lists it was
> > previusly
> > + * attached to. Needs to be called with the LRU lock held. The
> > function
> > + * can be called multiple times after eachother.
> > + */
> > +void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor
> > *cursor)
> > +{
> > +	lockdep_assert_held(&cursor->man->bdev->lru_lock);
> > +	list_del_init(&cursor->hitch.link);
> > +}
> > +
> > +/**
> > + * ttm_resource_cursor_fini() - Finalize the LRU list cursor usage
> > + * @cursor: The struct ttm_resource_cursor to finalize.
> > + *
> > + * The function pulls the LRU list cursor off any lists it was
> > previusly
> > + * attached to. Needs to be called without the LRU list lock held.
> > The
> > + * function can be called multiple times after eachother.
> > + */
> > +void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor)
> > +{
> > +	spinlock_t *lru_lock = &cursor->man->bdev->lru_lock;
> > +
> > +	spin_lock(lru_lock);
> > +	ttm_resource_cursor_fini_locked(cursor);
> > +	spin_unlock(lru_lock);
> > +}
> > +
> >   /**
> >    * ttm_lru_bulk_move_init - initialize a bulk move structure
> >    * @bulk: the structure to init
> > @@ -484,62 +515,63 @@ void ttm_resource_manager_debug(struct
> > ttm_resource_manager *man,
> >   EXPORT_SYMBOL(ttm_resource_manager_debug);
> >   
> >   /**
> > - * ttm_resource_manager_first
> > - *
> > - * @man: resource manager to iterate over
> > + * ttm_resource_manager_next() - Continue iterating over the
> > resource manager
> > + * resources
> >    * @cursor: cursor to record the position
> >    *
> > - * Returns the first resource from the resource manager.
> > + * Return: The next resource from the resource manager.
> >    */
> >   struct ttm_resource *
> > -ttm_resource_manager_first(struct ttm_resource_manager *man,
> > -			   struct ttm_resource_cursor *cursor)
> > +ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
> 
> Why are you switching first/next here? It took me a moment to realize
> that the two functions switched places.

Hmm. That was probably when _first() started using _next(), before
realizing they already had declarations. I'll change that back for
clarity.

> 
> >   {
> > +	struct ttm_resource_manager *man = cursor->man;
> >   	struct ttm_lru_item *lru;
> >   
> >   	lockdep_assert_held(&man->bdev->lru_lock);
> >   
> > -	for (cursor->priority = 0; cursor->priority <
> > TTM_MAX_BO_PRIORITY;
> > -	     ++cursor->priority)
> > -		list_for_each_entry(lru, &man->lru[cursor-
> > >priority], link) {
> > -			if (ttm_lru_item_is_res(lru))
> > +	do {
> > +		lru = &cursor->hitch;
> > +		list_for_each_entry_continue(lru, &man-
> > >lru[cursor->priority], link) {
> > +			if (ttm_lru_item_is_res(lru)) {
> > +				list_move(&cursor->hitch.link,
> > &lru->link);
> >   				return ttm_lru_item_to_res(lru);
> > +			}
> >   		}
> >   
> > +		if (++cursor->priority >= TTM_MAX_BO_PRIORITY)
> > +			break;
> > +
> > +		list_move(&cursor->hitch.link, &man->lru[cursor-
> > >priority]);
> > +	} while (true);
> > +
> > +	list_del_init(&cursor->hitch.link);
> > +
> >   	return NULL;
> >   }
> >   
> >   /**
> > - * ttm_resource_manager_next
> > - *
> > + * ttm_resource_manager_first() - Start iterating over the
> > resources
> > + * of a resource manager
> >    * @man: resource manager to iterate over
> >    * @cursor: cursor to record the position
> > - * @res: the current resource pointer
> >    *
> > - * Returns the next resource from the resource manager.
> > + * Initializes the cursor and starts iterating. When done
> > iterating,
> > + * the caller must explicitly call ttm_resource_cursor_fini().
> > + *
> > + * Return: The first resource from the resource manager.
> >    */
> >   struct ttm_resource *
> > -ttm_resource_manager_next(struct ttm_resource_manager *man,
> > -			  struct ttm_resource_cursor *cursor,
> > -			  struct ttm_resource *res)
> > +ttm_resource_manager_first(struct ttm_resource_manager *man,
> > +			   struct ttm_resource_cursor *cursor)
> >   {
> > -	struct ttm_lru_item *lru = &res->lru;
> > -
> >   	lockdep_assert_held(&man->bdev->lru_lock);
> >   
> > -	list_for_each_entry_continue(lru, &man->lru[cursor-
> > >priority], link) {
> > -		if (ttm_lru_item_is_res(lru))
> > -			return ttm_lru_item_to_res(lru);
> > -	}
> > +	cursor->priority = 0;
> > +	cursor->man = man;
> > +	ttm_lru_item_init(&cursor->hitch, TTM_LRU_HITCH);
> > +	list_move(&cursor->hitch.link, &man->lru[cursor-
> > >priority]);
> 
> That should probably be a list_add() instead.

Yes I can change that. The list head is initialized in
ttm_lru_item_init() so it's not really a bug, just slightly
inefficient.

/Thomas


> 
> Need to take a closer look what actually changed when the functions
> keep 
> their original order.
> 
> Christian.
> 
> >   
> > -	for (++cursor->priority; cursor->priority <
> > TTM_MAX_BO_PRIORITY;
> > -	     ++cursor->priority)
> > -		list_for_each_entry(lru, &man->lru[cursor-
> > >priority], link) {
> > -			if (ttm_lru_item_is_res(lru))
> > -				ttm_lru_item_to_res(lru);
> > -		}
> > -
> > -	return NULL;
> > +	return ttm_resource_manager_next(cursor);
> >   }
> >   
> >   static void ttm_kmap_iter_iomap_map_local(struct ttm_kmap_iter
> > *iter,
> > diff --git a/include/drm/ttm/ttm_resource.h
> > b/include/drm/ttm/ttm_resource.h
> > index 4babc4ff10b0..dfc01258c981 100644
> > --- a/include/drm/ttm/ttm_resource.h
> > +++ b/include/drm/ttm/ttm_resource.h
> > @@ -271,15 +271,23 @@ ttm_lru_item_to_res(struct ttm_lru_item
> > *item)
> >   
> >   /**
> >    * struct ttm_resource_cursor
> > - *
> > + * @man: The resource manager currently being iterated over
> > + * @hitch: A hitch list node inserted before the next resource
> > + * to iterate over.
> >    * @priority: the current priority
> >    *
> >    * Cursor to iterate over the resources in a manager.
> >    */
> >   struct ttm_resource_cursor {
> > +	struct ttm_resource_manager *man;
> > +	struct ttm_lru_item hitch;
> >   	unsigned int priority;
> >   };
> >   
> > +void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor
> > *cursor);
> > +
> > +void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor);
> > +
> >   /**
> >    * struct ttm_lru_bulk_move_pos
> >    *
> > @@ -438,9 +446,7 @@ struct ttm_resource *
> >   ttm_resource_manager_first(struct ttm_resource_manager *man,
> >   			   struct ttm_resource_cursor *cursor);
> >   struct ttm_resource *
> > -ttm_resource_manager_next(struct ttm_resource_manager *man,
> > -			  struct ttm_resource_cursor *cursor,
> > -			  struct ttm_resource *res);
> > +ttm_resource_manager_next(struct ttm_resource_cursor *cursor);
> >   
> >   /**
> >    * ttm_resource_manager_for_each_res - iterate over all resources
> > @@ -452,7 +458,7 @@ ttm_resource_manager_next(struct
> > ttm_resource_manager *man,
> >    */
> >   #define ttm_resource_manager_for_each_res(man, cursor,
> > res)		\
> >   	for (res = ttm_resource_manager_first(man, cursor);
> > res;	\
> > -	     res = ttm_resource_manager_next(man, cursor, res))
> > +	     res = ttm_resource_manager_next(cursor))
> >   
> >   struct ttm_kmap_iter *
> >   ttm_kmap_iter_iomap_init(struct ttm_kmap_iter_iomap *iter_io,
> 

Re: [RFC PATCH 0/8] TTM shrinker helpers and xe buffer object shrinker

[Thomas Hellström]

Hi, Amaranath,

On Tue, 2024-04-02 at 17:25 +0530, Somalapuram, Amaranath wrote:
> 
> On 3/29/2024 8:26 PM, Thomas Hellström wrote:
> > This series implements TTM shrinker / eviction helpers and an xe bo
> > shrinker. It builds on two previous series. First
> > 
> > https://www.mail-archive.com/dri-devel@lists.freedesktop.org/msg484425.html
> > 
> > for patch 1-4, which IMO still could be reviewed and pushed as a
> > separate series.
> > 
> > Second the previous TTM shrinker series 
> On the latest drm-misc good amount of conflicts on both patch series,
> able to re-base first one, Second on has 16 patches.
> If you have latest re-base patches, Please share it.

I was a bit unclear here. This series includes a rebased variant of the
first series, and the rest of this series is a rework of the remaining
patches in the second series below.

So this series is self-contained and the links are provided only for
reference and context. This series still seems to apply using git am -3
on drm-tip, and with a minor single conflict on drm-misc-next.
(Typically we send the patches against drm-tip since that's what CI is
using).

The below series has not been rebased but I have a version of this
series with a direct-swap-cache insertion backend lying around
somewhere. I can post it or share it on gitlab if you want.

Thanks,
/Thomas



> 
> Regards,
> S.Amarnath
> > https://lore.kernel.org/linux-mm/b7491378-defd-4f1c-31e2-29e4c77e2d67@amd.com/T/
> > 
> > Where the comment about layering
> > https://lore.kernel.org/linux-mm/b7491378-defd-4f1c-31e2-29e4c77e2d67@amd.com/T/#ma918844aa8a6efe8768fdcda0c6590d5c93850c9
> > 
> > now addressed, and this version also implements shmem objects for
> > backup
> > rather than direct swap-cache insertions, which was used in the
> > previuos
> > series. It turns out that with per-page backup / shrinking, shmem
> > objects
> > appears to work just as well as direct swap-cache insertions with
> > the
> > added benefit that was introduced in the previous TTM shrinker
> > series to
> > avoid running out of swap entries isn't really needed.
> > 
> > In any case, patch 1-4 are better described in their separate
> > series.
> > (RFC is removed for those).
> > 
> > Patch 5 could in theory be skipped but introduces a possibility to
> > easily
> > add or test multiple backup backends, like the direct swap-cache
> > insertion or even files into fast dedicated nvme storage for for
> > example.
> > 
> > Patch 6 introduces helpers in the ttm_pool code for page-by-page
> > shrinking
> > and recovery. It avoids having to temporarily allocate a huge
> > amount of
> > memory to be able to shrink a buffer object. It also introduces the
> > possibility to immediately write-back pages if needed, since that
> > tends
> > to be a bit delayed when left to kswapd.
> > 
> > Patch 7 introduces a LRU walk helper for eviction and shrinking.
> > It's
> > currently xe-only but not xe-specific and can easily be moved to
> > TTM when
> > used by more than one driver or when eviction is implemented using
> > it.
> > 
> > Patch 8 introduces a helper callback for shrinking (Also ready to
> > be
> > moved to TTM) and an xe-specific shrinker implementation.
> > 
> > Testing:
> > ATM I don't think we have good tests to cover the shrinking
> > functionality
> > The series has been tested with a hack that continously creates
> > TTM_TT buffer objects until system memory and swap space is
> > exhausted,
> > and then reads them back and frees them. However, these tests
> > seem to be very slow.
> > Ideally a similar test on a machine with very fast solid state or
> > similar storage should be set up. Ideally also verifying content
> > preservation.
> > 
> > Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
> > Cc: Christian König <christian.koenig@amd.com>
> > Cc: <dri-devel@lists.freedesktop.org>
> > 
> > Thomas Hellström (8):
> >    drm/ttm: Allow TTM LRU list nodes of different types
> >    drm/ttm: Use LRU hitches
> >    drm/ttm, drm/amdgpu, drm/xe: Consider hitch moves within bulk
> > sublist
> >      moves
> >    drm/ttm: Allow continued swapout after -ENOSPC falure
> >    drm/ttm: Add a virtual base class for graphics memory backup
> >    drm/ttm/pool: Provide a helper to shrink pages.
> >    drm/xe, drm/ttm: Provide a generic LRU walker helper
> >    drm/xe: Add a shrinker for xe bos
> > 
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c |   4 +
> >   drivers/gpu/drm/ttm/Makefile           |   2 +-
> >   drivers/gpu/drm/ttm/ttm_backup_shmem.c | 137 +++++++++
> >   drivers/gpu/drm/ttm/ttm_bo.c           |   1 +
> >   drivers/gpu/drm/ttm/ttm_device.c       |  33 ++-
> >   drivers/gpu/drm/ttm/ttm_pool.c         | 391
> > ++++++++++++++++++++++++-
> >   drivers/gpu/drm/ttm/ttm_resource.c     | 231 ++++++++++++---
> >   drivers/gpu/drm/ttm/ttm_tt.c           |  34 +++
> >   drivers/gpu/drm/xe/Makefile            |   2 +
> >   drivers/gpu/drm/xe/xe_bo.c             | 123 ++++++--
> >   drivers/gpu/drm/xe/xe_bo.h             |   3 +
> >   drivers/gpu/drm/xe/xe_device.c         |   8 +
> >   drivers/gpu/drm/xe/xe_device_types.h   |   2 +
> >   drivers/gpu/drm/xe/xe_shrinker.c       | 237 +++++++++++++++
> >   drivers/gpu/drm/xe/xe_shrinker.h       |  18 ++
> >   drivers/gpu/drm/xe/xe_ttm_helpers.c    | 224 ++++++++++++++
> >   drivers/gpu/drm/xe/xe_ttm_helpers.h    |  63 ++++
> >   drivers/gpu/drm/xe/xe_vm.c             |   4 +
> >   include/drm/ttm/ttm_backup.h           | 136 +++++++++
> >   include/drm/ttm/ttm_device.h           |   2 +
> >   include/drm/ttm/ttm_pool.h             |   4 +
> >   include/drm/ttm/ttm_resource.h         |  96 +++++-
> >   include/drm/ttm/ttm_tt.h               |  19 ++
> >   23 files changed, 1683 insertions(+), 91 deletions(-)
> >   create mode 100644 drivers/gpu/drm/ttm/ttm_backup_shmem.c
> >   create mode 100644 drivers/gpu/drm/xe/xe_shrinker.c
> >   create mode 100644 drivers/gpu/drm/xe/xe_shrinker.h
> >   create mode 100644 drivers/gpu/drm/xe/xe_ttm_helpers.c
> >   create mode 100644 drivers/gpu/drm/xe/xe_ttm_helpers.h
> >   create mode 100644 include/drm/ttm/ttm_backup.h
> >