drm/radeon: limit how much memory TTM can move per IB according to VRAM usage

Signed-off-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>

3 files changed, 85 insertions, 8 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_cs.c b/drivers/gpu/drm/radeon/radeon_cs.c
index 07e165128dbf..5abae403ea4f 100644
--- a/drivers/gpu/drm/radeon/radeon_cs.c
+++ b/drivers/gpu/drm/radeon/radeon_cs.c
@@ -168,7 +168,7 @@ static int radeon_cs_parser_relocs(struct radeon_cs_parser *p)
 
         radeon_cs_buckets_get_list(&buckets, &p->validated);
 
-        return radeon_bo_list_validate(&p->ticket, &p->validated, p->ring);
+        return radeon_bo_list_validate(p->rdev, &p->ticket, &p->validated, p->ring);
 }
 
 static int radeon_cs_get_ring(struct radeon_cs_parser *p, u32 ring, s32 priority)
diff --git a/drivers/gpu/drm/radeon/radeon_object.c b/drivers/gpu/drm/radeon/radeon_object.c
index 8399fe021769..ed03f2d15853 100644
--- a/drivers/gpu/drm/radeon/radeon_object.c
+++ b/drivers/gpu/drm/radeon/radeon_object.c
@@ -366,29 +366,105 @@ void radeon_bo_fini(struct radeon_device *rdev)
         arch_phys_wc_del(rdev->mc.vram_mtrr);
 }
 
-int radeon_bo_list_validate(struct ww_acquire_ctx *ticket,
+/* Returns how many bytes TTM can move per IB.
+ */
+static u64 radeon_bo_get_threshold_for_moves(struct radeon_device *rdev)
+{
+        u64 real_vram_size = rdev->mc.real_vram_size;
+        u64 vram_usage = atomic64_read(&rdev->vram_usage);
+
+        /* This function is based on the current VRAM usage.
+         *
+         * - If all of VRAM is free, allow relocating the number of bytes that
+         *   is equal to 1/4 of the size of VRAM for this IB.
+
+         * - If more than one half of VRAM is occupied, only allow relocating
+         *   1 MB of data for this IB.
+         *
+         * - From 0 to one half of used VRAM, the threshold decreases
+         *   linearly.
+         *         __________________
+         * 1/4 of -|\               |
+         * VRAM    | \              |
+         *         |  \             |
+         *         |   \            |
+         *         |    \           |
+         *         |     \          |
+         *         |      \         |
+         *         |       \________|1 MB
+         *         |----------------|
+         *    VRAM 0 %             100 %
+         *         used            used
+         *
+         * Note: It's a threshold, not a limit. The threshold must be crossed
+         * for buffer relocations to stop, so any buffer of an arbitrary size
+         * can be moved as long as the threshold isn't crossed before
+         * the relocation takes place. We don't want to disable buffer
+         * relocations completely.
+         *
+         * The idea is that buffers should be placed in VRAM at creation time
+         * and TTM should only do a minimum number of relocations during
+         * command submission. In practice, you need to submit at least
+         * a dozen IBs to move all buffers to VRAM if they are in GTT.
+         *
+         * Also, things can get pretty crazy under memory pressure and actual
+         * VRAM usage can change a lot, so playing safe even at 50% does
+         * consistently increase performance.
+         */
+
+        u64 half_vram = real_vram_size >> 1;
+        u64 half_free_vram = vram_usage >= half_vram ? 0 : half_vram - vram_usage;
+        u64 bytes_moved_threshold = half_free_vram >> 1;
+        return max(bytes_moved_threshold, 1024*1024ull);
+}
+
+int radeon_bo_list_validate(struct radeon_device *rdev,
+                            struct ww_acquire_ctx *ticket,
                             struct list_head *head, int ring)
 {
         struct radeon_bo_list *lobj;
         struct radeon_bo *bo;
-        u32 domain;
         int r;
+        u64 bytes_moved = 0, initial_bytes_moved;
+        u64 bytes_moved_threshold = radeon_bo_get_threshold_for_moves(rdev);
 
         r = ttm_eu_reserve_buffers(ticket, head);
         if (unlikely(r != 0)) {
                 return r;
         }
+
         list_for_each_entry(lobj, head, tv.head) {
                 bo = lobj->bo;
                 if (!bo->pin_count) {
-                        domain = lobj->domain;
-                        
+                        u32 domain = lobj->domain;
+                        u32 current_domain =
+                                radeon_mem_type_to_domain(bo->tbo.mem.mem_type);
+
+                        /* Check if this buffer will be moved and don't move it
+                         * if we have moved too many buffers for this IB already.
+                         *
+                         * Note that this allows moving at least one buffer of
+                         * any size, because it doesn't take the current "bo"
+                         * into account. We don't want to disallow buffer moves
+                         * completely.
+                         */
+                        if (current_domain != RADEON_GEM_DOMAIN_CPU &&
+                            (domain & current_domain) == 0 && /* will be moved */
+                            bytes_moved > bytes_moved_threshold) {
+                                /* don't move it */
+                                domain = current_domain;
+                        }
+
                 retry:
                         radeon_ttm_placement_from_domain(bo, domain);
                         if (ring == R600_RING_TYPE_UVD_INDEX)
                                 radeon_uvd_force_into_uvd_segment(bo);
-                        r = ttm_bo_validate(&bo->tbo, &bo->placement,
-                                                true, false);
+
+                        initial_bytes_moved = atomic64_read(&rdev->num_bytes_moved);
+                        r = ttm_bo_validate(&bo->tbo, &bo->placement, true, false);
+                        bytes_moved += atomic64_read(&rdev->num_bytes_moved) -
+                                       initial_bytes_moved;
+
                         if (unlikely(r)) {
                                 if (r != -ERESTARTSYS && domain != lobj->alt_domain) {
                                         domain = lobj->alt_domain;
diff --git a/drivers/gpu/drm/radeon/radeon_object.h b/drivers/gpu/drm/radeon/radeon_object.h
index 6c3ca9edc2f4..7dff64d1f592 100644
--- a/drivers/gpu/drm/radeon/radeon_object.h
+++ b/drivers/gpu/drm/radeon/radeon_object.h
@@ -138,7 +138,8 @@ extern int radeon_bo_evict_vram(struct radeon_device *rdev);
 extern void radeon_bo_force_delete(struct radeon_device *rdev);
 extern int radeon_bo_init(struct radeon_device *rdev);
 extern void radeon_bo_fini(struct radeon_device *rdev);
-extern int radeon_bo_list_validate(struct ww_acquire_ctx *ticket,
+extern int radeon_bo_list_validate(struct radeon_device *rdev,
+                                   struct ww_acquire_ctx *ticket,
                                    struct list_head *head, int ring);
 extern int radeon_bo_fbdev_mmap(struct radeon_bo *bo,
                                 struct vm_area_struct *vma);