[Intel-gfx] [PATCH 03/20] drm: implement a method to free unused pages

Matthew Auld
2022-01-26T15:22:21Z

From: Arunpravin <Arunpravin.PaneerSelvam@amd.com>

On contiguous allocation, we round up the size
to the *next* power of 2, implement a function
to free the unused pages after the newly allocate block.

v2(Matthew Auld):
- replace function name 'drm_buddy_free_unused_pages' with
drm_buddy_block_trim
- replace input argument name 'actual_size' with 'new_size'
- add more validation checks for input arguments
- add overlaps check to avoid needless searching and splitting
- merged the below patch to see the feature in action
- add free unused pages support to i915 driver
- lock drm_buddy_block_trim() function as it calls mark_free/mark_split
are all globally visible

v3(Matthew Auld):
- remove trim method error handling as we address the failure case
at drm_buddy_block_trim() function

v4:
- in case of trim, at __alloc_range() split_block failure path
marks the block as free and removes it from the original list,
potentially also freeing it, to overcome this problem, we turn
the drm_buddy_block_trim() input node into a temporary node to
prevent recursively freeing itself, but still retain the
un-splitting/freeing of the other nodes(Matthew Auld)

- modify the drm_buddy_block_trim() function return type

v5(Matthew Auld):
- revert drm_buddy_block_trim() function return type changes in v4
- modify drm_buddy_block_trim() passing argument n_pages to original_size
as n_pages has already been rounded up to the next power-of-two and
passing n_pages results noop

v6:
- fix warnings reported by kernel test robot <lkp@intel.com>

Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@amd.com>
---
drivers/gpu/drm/drm_buddy.c | 65 +++++++++++++++++++
drivers/gpu/drm/i915/i915_ttm_buddy_manager.c | 10 +++
include/drm/drm_buddy.h | 4 ++
3 files changed, 79 insertions(+)

diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index 6aa5c1ce25bf..c5902a81b8c5 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -546,6 +546,71 @@ static int __drm_buddy_alloc_range(struct drm_buddy *mm,
return __alloc_range(mm, &dfs, start, size, blocks);
}

+/**
+ * drm_buddy_block_trim - free unused pages
+ *
+ * @mm: DRM buddy manager
+ * @new_size: original size requested
+ * @blocks: output list head to add allocated blocks
+ *
+ * For contiguous allocation, we round up the size to the nearest
+ * power of two value, drivers consume *actual* size, so remaining
+ * portions are unused and it can be freed.
+ *
+ * Returns:
+ * 0 on success, error code on failure.
+ */
+int drm_buddy_block_trim(struct drm_buddy *mm,
+ u64 new_size,
+ struct list_head *blocks)
+{
+ struct drm_buddy_block *parent;
+ struct drm_buddy_block *block;
+ LIST_HEAD(dfs);
+ u64 new_start;
+ int err;
+
+ if (!list_is_singular(blocks))
+ return -EINVAL;
+
+ block = list_first_entry(blocks,
+ struct drm_buddy_block,
+ link);
+
+ if (!drm_buddy_block_is_allocated(block))
+ return -EINVAL;
+
+ if (new_size > drm_buddy_block_size(mm, block))
+ return -EINVAL;
+
+ if (!new_size && !IS_ALIGNED(new_size, mm->chunk_size))
+ return -EINVAL;
+
+ if (new_size == drm_buddy_block_size(mm, block))
+ return 0;
+
+ list_del(&block->link);
+ mark_free(mm, block);
+ mm->avail += drm_buddy_block_size(mm, block);
+
+ /* Prevent recursively freeing this node */
+ parent = block->parent;
+ block->parent = NULL;
+
+ new_start = drm_buddy_block_offset(block);
+ list_add(&block->tmp_link, &dfs);
+ err = __alloc_range(mm, &dfs, new_start, new_size, blocks);
+ if (err) {
+ mark_allocated(block);
+ mm->avail -= drm_buddy_block_size(mm, block);
+ list_add(&block->link, blocks);
+ }
+
+ block->parent = parent;
+ return err;
+}
+EXPORT_SYMBOL(drm_buddy_block_trim);
+
/**
* drm_buddy_alloc_blocks - allocate power-of-two blocks
*
diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
index 3662434b64bb..53eb100688a6 100644
--- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
+++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
@@ -97,6 +97,16 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
if (unlikely(err))
goto err_free_blocks;

+ if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
+ u64 original_size = (u64)bman_res->base.num_pages << PAGE_SHIFT;
+
+ mutex_lock(&bman->lock);
+ drm_buddy_block_trim(mm,
+ original_size,
+ &bman_res->blocks);
+ mutex_unlock(&bman->lock);
+ }
+
*res = &bman_res->base;
return 0;

diff --git a/include/drm/drm_buddy.h b/include/drm/drm_buddy.h
index 424fc443115e..17ca928fce8e 100644
--- a/include/drm/drm_buddy.h
+++ b/include/drm/drm_buddy.h
@@ -145,6 +145,10 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
struct list_head *blocks,
unsigned long flags);

+int drm_buddy_block_trim(struct drm_buddy *mm,
+ u64 new_size,
+ struct list_head *blocks);
+
void drm_buddy_free_block(struct drm_buddy *mm, struct drm_buddy_block *block);

void drm_buddy_free_list(struct drm_buddy *mm, struct list_head *objects);
--
2.34.1