[Intel-gfx] [PATCH] drm/i915: Remove guard page insertion around unevictable nodes
Matthew Auld
matthew.william.auld at gmail.com
Mon Jan 25 11:16:13 UTC 2021
On Sun, 24 Jan 2021 at 13:57, Chris Wilson <chris at chris-wilson.co.uk> wrote:
>
> Assume that unevictable nodes are not in the GTT and so we can ignore
> page boundary concerns, and so allow regular nodes to abutt against
> irregular unevictable nodes.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
> drivers/gpu/drm/i915/i915_drv.h | 2 --
> drivers/gpu/drm/i915/i915_gem_evict.c | 6 ++++--
> drivers/gpu/drm/i915/i915_vma.h | 10 +++++++++-
> drivers/gpu/drm/i915/i915_vma_types.h | 2 ++
> 4 files changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 99cf861df92d..69c5a185ecff 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -357,8 +357,6 @@ enum i915_cache_level {
> I915_CACHE_WT, /* hsw:gt3e WriteThrough for scanouts */
> };
>
> -#define I915_COLOR_UNEVICTABLE (-1) /* a non-vma sharing the address space */
> -
> struct intel_fbc {
> /* This is always the inner lock when overlapping with struct_mutex and
> * it's the outer lock when overlapping with stolen_lock. */
> diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c b/drivers/gpu/drm/i915/i915_gem_evict.c
> index 4d2d59a9942b..aef88fdb9f66 100644
> --- a/drivers/gpu/drm/i915/i915_gem_evict.c
> +++ b/drivers/gpu/drm/i915/i915_gem_evict.c
> @@ -313,11 +313,13 @@ int i915_gem_evict_for_node(struct i915_address_space *vm,
> */
> if (i915_vm_has_cache_coloring(vm)) {
> if (node->start + node->size == target->start) {
> - if (node->color == target->color)
> + if (i915_node_color_matches(node,
> + target->color))
> continue;
> }
> if (node->start == target->start + target->size) {
> - if (node->color == target->color)
> + if (i915_node_color_matches(node,
> + target->color))
> continue;
> }
> }
Since we bail early on seeing COLOR_UNEVICTABLE, and since we have to
enlarge our search space by a page on both ends, do we need something
like:
@@ -291,18 +291,22 @@ int i915_gem_evict_for_node(struct i915_address_space *vm,
/* Always look at the page afterwards to avoid the end-of-GTT */
end += I915_GTT_PAGE_SIZE;
+
+ /*
+ * The special head node is marked as I915_COLOR_UNEVICTABLE to
+ * prevent normal vma from using the last page, in order to
+ * prevent prefetching over the boundary. If we are dealing with
+ * a normal vma and we abutt with the head node we will always
+ * get -ENOSPC as per the color adjust later, so just bail
+ * early???
+ */
+ if (target->color != I915_COLOR_UNEVICTABLE && end >= vm->total)
+ return -ENOSPC;
}
GEM_BUG_ON(start >= end);
drm_mm_for_each_node_in_range(node, &vm->mm, start, end) {
- /* If we find any non-objects (!vma), we cannot evict them */
- if (node->color == I915_COLOR_UNEVICTABLE) {
- ret = -ENOSPC;
- break;
- }
-
GEM_BUG_ON(!drm_mm_node_allocated(node));
- vma = container_of(node, typeof(*vma), node);
/*
* If we are using coloring to insert guard pages between
@@ -310,6 +314,9 @@ int i915_gem_evict_for_node(struct i915_address_space *vm,
* to check whether the objects on either side of our range
* abutt and conflict. If they are in conflict, then we evict
* those as well to make room for our guard pages.
+ *
+ * Also consider I915_COLOR_UNEVICTABLE nodes, since we consider
+ * these special and permit abutting on either end.
*/
if (i915_vm_has_cache_coloring(vm)) {
if (node->start + node->size == target->start) {
@@ -324,6 +331,14 @@ int i915_gem_evict_for_node(struct i915_address_space *vm,
}
}
+ /* If we find any non-objects (!vma), we cannot evict them */
+ if (node->color == I915_COLOR_UNEVICTABLE) {
+ ret = -ENOSPC;
+ break;
+ }
+
+ vma = container_of(node, typeof(*vma), node);
+
if (i915_vma_is_pinned(vma)) {
ret = -ENOSPC;
break;
> diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
> index a64adc8c883b..dac953815118 100644
> --- a/drivers/gpu/drm/i915/i915_vma.h
> +++ b/drivers/gpu/drm/i915/i915_vma.h
> @@ -283,10 +283,18 @@ static inline bool i915_vma_is_bound(const struct i915_vma *vma,
> return atomic_read(&vma->flags) & where;
> }
>
> +static inline bool i915_node_color_matches(const struct drm_mm_node *node,
> + unsigned long color)
> +{
> + return (node->color | color) == I915_COLOR_UNEVICTABLE ||
> + node->color == color;
> +}
> +
> static inline bool i915_node_color_differs(const struct drm_mm_node *node,
> unsigned long color)
> {
> - return drm_mm_node_allocated(node) && node->color != color;
> + return drm_mm_node_allocated(node) &&
> + !i915_node_color_matches(node, color);
> }
>
> /**
> diff --git a/drivers/gpu/drm/i915/i915_vma_types.h b/drivers/gpu/drm/i915/i915_vma_types.h
> index f5cb848b7a7e..e72a07692a64 100644
> --- a/drivers/gpu/drm/i915/i915_vma_types.h
> +++ b/drivers/gpu/drm/i915/i915_vma_types.h
> @@ -95,6 +95,8 @@ enum i915_cache_level;
> *
> */
>
> +#define I915_COLOR_UNEVICTABLE (-1) /* a non-vma sharing the address space */
> +
> struct intel_remapped_plane_info {
> /* in gtt pages */
> unsigned int width, height, stride, offset;
> --
> 2.20.1
>
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