[PATCH 04/17] drm/i915: Fix i915_gem_evict_for_vma (soft-pinning)

Chris Wilson
2016-08-22T08:04:08Z

Soft-pinning depends upon being able to check for availabilty of an
inverval and evict overlapping object fro a drm_mm range manager very
quickly. Currently it uses a linear list which makes performance dire,
and softpinning not a suitable replacement.

It also helps if the routine reports the correct error codes as expected
by its callers and emits a tracepoint upon use.

For posterity since the wrong patch was pushed (i.e. that missed these
key points), this is the changelog that should have been on commit
506a8e87d8d2 ("drm/i915: Add soft-pinning API for execbuffer"):

Userspace can pass in an offset that it presumes the object is located
at. The kernel will then do its utmost to fit the object into that
location. The assumption is that userspace is handling its own object
locations (for example along with full-ppgtt) and that the kernel will
rarely have to make space for the user's requests.

This extends the DRM_IOCTL_I915_GEM_EXECBUFFER2 to do the following:
* if the user supplies a virtual address via the execobject->offset
*and* sets the EXEC_OBJECT_PINNED flag in execobject->flags, then
that object is placed at that offset in the address space selected
by the context specifier in execbuffer.
* the location must be aligned to the GTT page size, 4096 bytes
* as the object is placed exactly as specified, it may be used by this
execbuffer call without relocations pointing to it

It may fail to do so if:
* EINVAL is returned if the object does not have a 4096 byte aligned
address
* the object conflicts with another pinned object (either pinned by
hardware in that address space, e.g. scanouts in the aliasing ppgtt)
or within the same batch.
EBUSY is returned if the location is pinned by hardware
EINVAL is returned if the location is already in use by the batch
* EINVAL is returned if the object conflicts with its own alignment (as meets
the hardware requirements) or if the placement of the object does not fit
within the address space

All other execbuffer errors apply.

Presence of this execbuf extension may be queried by passing
I915_PARAM_HAS_EXEC_SOFTPIN to DRM_IOCTL_I915_GETPARAM and checking for
a reported value of 1 (or greater).

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
drivers/gpu/drm/drm_mm.c | 9 +++
drivers/gpu/drm/i915/i915_drv.h | 3 +-
drivers/gpu/drm/i915/i915_gem.c | 12 +---
drivers/gpu/drm/i915/i915_gem_evict.c | 88 +++++++++++++++++++++---------
drivers/gpu/drm/i915/i915_gem_execbuffer.c | 2 +-
drivers/gpu/drm/i915/i915_gem_gtt.c | 10 ++--
drivers/gpu/drm/i915/i915_trace.h | 23 ++++++++
7 files changed, 105 insertions(+), 42 deletions(-)

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index 11d44a1e0ab3..a13215a525e6 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -275,6 +275,15 @@ int drm_mm_reserve_node(struct drm_mm *mm, struct drm_mm_node *node)
if (hole_start > node->start || hole_end < end)
return -ENOSPC;

+ if (mm->color_adjust) {
+ u64 adj_start = hole_start, adj_end = hole_end;
+
+ mm->color_adjust(hole, node->color, &adj_start, &adj_end);
+ if (adj_start > node->start ||
+ adj_end < node->start + node->size)
+ return -ENOSPC;
+ }
+
node->mm = mm;
node->allocated = 1;

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index a85316be9116..30ae14870c47 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3470,7 +3470,8 @@ int __must_check i915_gem_evict_something(struct i915_address_space *vm,
unsigned cache_level,
u64 start, u64 end,
unsigned flags);
-int __must_check i915_gem_evict_for_vma(struct i915_vma *target);
+int __must_check i915_gem_evict_for_vma(struct i915_vma *vma,
+ unsigned int flags);
int i915_gem_evict_vm(struct i915_address_space *vm, bool do_idle);

/* belongs in i915_gem_gtt.h */
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 0a48c90979a9..de895c7ef9e6 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -68,8 +68,8 @@ insert_mappable_node(struct drm_i915_private *i915,
{
memset(node, 0, sizeof(*node));
return drm_mm_insert_node_in_range_generic(&i915->ggtt.base.mm, node,
- size, 0, 0, 0,
- i915->ggtt.mappable_end,
+ size, 0, -1,
+ 0, i915->ggtt.mappable_end,
DRM_MM_SEARCH_DEFAULT,
DRM_MM_CREATE_DEFAULT);
}
@@ -2966,12 +2966,6 @@ static bool i915_gem_valid_gtt_space(struct i915_vma *vma,
if (vma->vm->mm.color_adjust == NULL)
return true;

- if (!drm_mm_node_allocated(gtt_space))
- return true;
-
- if (list_empty(&gtt_space->node_list))
- return true;
-
other = list_entry(gtt_space->node_list.prev, struct drm_mm_node, node_list);
if (other->allocated && !other->hole_follows && other->color != cache_level)
return false;
@@ -3056,7 +3050,7 @@ i915_vma_insert(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
vma->node.color = obj->cache_level;
ret = drm_mm_reserve_node(&vma->vm->mm, &vma->node);
if (ret) {
- ret = i915_gem_evict_for_vma(vma);
+ ret = i915_gem_evict_for_vma(vma, flags);
if (ret == 0)
ret = drm_mm_reserve_node(&vma->vm->mm, &vma->node);
if (ret)
diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c b/drivers/gpu/drm/i915/i915_gem_evict.c
index 815d5fbe07ac..a8f6825cf14f 100644
--- a/drivers/gpu/drm/i915/i915_gem_evict.c
+++ b/drivers/gpu/drm/i915/i915_gem_evict.c
@@ -205,43 +205,81 @@ found:
return ret;
}

-int
-i915_gem_evict_for_vma(struct i915_vma *target)
+int i915_gem_evict_for_vma(struct i915_vma *target, unsigned int flags)
{
- struct drm_mm_node *node, *next;
+ struct list_head eviction_list;
+ struct drm_mm_node *node;
+ u64 start = target->node.start;
+ u64 end = start + target->node.size - 1;
+ struct i915_vma *vma, *next;
+ bool check_snoop;
+ int ret = 0;

- list_for_each_entry_safe(node, next,
- &target->vm->mm.head_node.node_list,
- node_list) {
- struct i915_vma *vma;
- int ret;
+ trace_i915_gem_evict_vma(target, flags);

- if (node->start + node->size <= target->node.start)
- continue;
- if (node->start >= target->node.start + target->node.size)
+ check_snoop = target->vm->mm.color_adjust;
+ if (check_snoop) {
+ if (start > target->vm->start)
+ start -= 4096;
+ if (end < target->vm->start + target->vm->total)
+ end += 4096;
+ }
+
+ node = drm_mm_interval_first(&target->vm->mm, start, end);
+ if (!node)
+ return 0;
+
+ INIT_LIST_HEAD(&eviction_list);
+ vma = container_of(node, typeof(*vma), node);
+ list_for_each_entry_from(vma,
+ &target->vm->mm.head_node.node_list,
+ node.node_list) {
+ if (vma->node.start > end)
break;

- vma = container_of(node, typeof(*vma), node);
+ if (check_snoop) {
+ if (vma->node.start + vma->node.size == target->node.start) {
+ if (vma->node.color == target->node.color)
+ continue;
+ }
+ if (vma->node.start == target->node.start + target->node.size) {
+ if (vma->node.color == target->node.color)
+ continue;
+ }
+ }

- if (i915_vma_is_pinned(vma)) {
- if (!vma->exec_entry || i915_vma_pin_count(vma) > 1)
- /* Object is pinned for some other use */
- return -EBUSY;
+ if (vma->node.color == -1) {
+ ret = -ENOSPC;
+ break;
+ }

- /* We need to evict a buffer in the same batch */
- if (vma->exec_entry->flags & EXEC_OBJECT_PINNED)
- /* Overlapping fixed objects in the same batch */
- return -EINVAL;
+ if (flags & PIN_NONBLOCK &&
+ (i915_vma_is_pinned(vma) || i915_vma_is_active(vma))) {
+ ret = -ENOSPC;
+ break;
+ }

- return -ENOSPC;
+ /* Overlap of objects in the same batch? */
+ if (i915_vma_is_pinned(vma)) {
+ ret = -ENOSPC;
+ if (vma->exec_entry &&
+ vma->exec_entry->flags & EXEC_OBJECT_PINNED)
+ ret = -EINVAL;
+ break;
}

- ret = i915_vma_unbind(vma);
- if (ret)
- return ret;
+ __i915_vma_pin(vma);
+ list_add(&vma->exec_list, &eviction_list);
}

- return 0;
+ list_for_each_entry_safe(vma, next, &eviction_list, exec_list) {
+ list_del_init(&vma->exec_list);
+ __i915_vma_unpin(vma);
+ if (ret == 0)
+ ret = i915_vma_unbind(vma);
+ }
+
+ return ret;
}

/**
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index fb1a64738fb8..3a5f43960cb6 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -445,7 +445,7 @@ static void *reloc_iomap(struct drm_i915_gem_object *obj,
memset(&cache->node, 0, sizeof(cache->node));
ret = drm_mm_insert_node_in_range_generic
(&ggtt->base.mm, &cache->node,
- 4096, 0, 0,
+ 4096, 0, -1,
0, ggtt->mappable_end,
DRM_MM_SEARCH_DEFAULT,
DRM_MM_CREATE_DEFAULT);
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 435c3fc73e18..0061c3841760 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -1996,16 +1996,14 @@ static int gen6_ppgtt_allocate_page_directories(struct i915_hw_ppgtt *ppgtt)
return ret;

alloc:
- ret = drm_mm_insert_node_in_range_generic(&ggtt->base.mm,
- &ppgtt->node, GEN6_PD_SIZE,
- GEN6_PD_ALIGN, 0,
- 0, ggtt->base.total,
+ ret = drm_mm_insert_node_in_range_generic(&ggtt->base.mm, &ppgtt->node,
+ GEN6_PD_SIZE, GEN6_PD_ALIGN,
+ -1, 0, ggtt->base.total,
DRM_MM_TOPDOWN);
if (ret == -ENOSPC && !retried) {
ret = i915_gem_evict_something(&ggtt->base,
GEN6_PD_SIZE, GEN6_PD_ALIGN,
- I915_CACHE_NONE,
- 0, ggtt->base.total,
+ -1, 0, ggtt->base.total,
0);
if (ret)
goto err_out;
diff --git a/drivers/gpu/drm/i915/i915_trace.h b/drivers/gpu/drm/i915/i915_trace.h
index 178798002a73..7a46e7c8a0cd 100644
--- a/drivers/gpu/drm/i915/i915_trace.h
+++ b/drivers/gpu/drm/i915/i915_trace.h
@@ -450,6 +450,29 @@ TRACE_EVENT(i915_gem_evict_vm,
TP_printk("dev=%d, vm=%p", __entry->dev, __entry->vm)
);

+TRACE_EVENT(i915_gem_evict_vma,
+ TP_PROTO(struct i915_vma *vma, unsigned int flags),
+ TP_ARGS(vma, flags),
+
+ TP_STRUCT__entry(
+ __field(u32, dev)
+ __field(struct i915_address_space *, vm)
+ __field(u64, start)
+ __field(u64, size)
+ __field(unsigned int, flags)
+ ),
+
+ TP_fast_assign(
+ __entry->dev = vma->vm->dev->primary->index;
+ __entry->vm = vma->vm;
+ __entry->start = vma->node.start;
+ __entry->size = vma->node.size;
+ __entry->flags = flags;
+ ),
+
+ TP_printk("dev=%d, vm=%p, start=%llx size=%llx, flags=%x", __entry->dev, __entry->vm, (long long)__entry->start, (long long)__entry->size, __entry->flags)
+);
+
TRACE_EVENT(i915_gem_ring_sync_to,
TP_PROTO(struct drm_i915_gem_request *to,
struct drm_i915_gem_request *from),
--
2.9.3