When the AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED flag is given by userspace,
it should only be treated as a hint to initially place a BO somewhere CPU
accessible, rather than having a permanent effect on BO placement.
Instead of the flag being set in stone at BO creation, set the flag when a
page fault occurs so that it goes somewhere CPU-visible, and clear it when
the BO is requested by the GPU.
However, clearing the CPU_ACCESS_REQUIRED flag may move a BO to invisible
VRAM, which is likely to cause a page fault that moves it right back to
GTT. When this happens too much, it is highly detrimental to performance.
Only clear the flag on CS if:
- The BO wasn't page faulted for a certain amount of time (currently 10
seconds, measured with jiffies), and
- its last page fault didn't occur too soon (currently 500ms) after its
last CS request, or vice versa.
Setting the flag in amdgpu_fault_reserve_notify() also means that we can
remove the loop to restrict lpfn to the end of visible VRAM, because
amdgpu_ttm_placement_init() will do it for us.
Signed-off-by: John Brooks <john@xxxxxxxxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 1 +
drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 46 ++++++++++++++++++++++--------
drivers/gpu/drm/amd/amdgpu/amdgpu_object.h | 1 +
3 files changed, 36 insertions(+), 12 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index 2fad8bd..73d6882 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -320,6 +320,7 @@ static int amdgpu_cs_bo_validate(struct amdgpu_cs_parser *p,
else
domain = bo->allowed_domains;
+ amdgpu_bo_clear_cpu_access_required(bo);
retry:
amdgpu_ttm_placement_from_domain(bo, domain);
initial_bytes_moved = atomic64_read(&adev->num_bytes_moved);
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
index 31d1f21..a7d48a7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
@@ -967,8 +967,8 @@ int amdgpu_bo_fault_reserve_notify(struct ttm_buffer_object *bo)
{
struct amdgpu_device *adev = amdgpu_ttm_adev(bo->bdev);
struct amdgpu_bo *abo;
- unsigned long offset, size, lpfn;
- int i, r;
+ unsigned long offset, size;
+ int r;
if (!amdgpu_ttm_bo_is_amdgpu_bo(bo))
return 0;
@@ -991,18 +991,9 @@ int amdgpu_bo_fault_reserve_notify(struct ttm_buffer_object *bo)
/* hurrah the memory is not visible ! */
atomic64_inc(&adev->num_vram_cpu_page_faults);
+ abo->flags |= AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED;
amdgpu_ttm_placement_from_domain(abo, AMDGPU_GEM_DOMAIN_VRAM |
AMDGPU_GEM_DOMAIN_GTT);
- lpfn = adev->mc.visible_vram_size >> PAGE_SHIFT;
- for (i = 0; i < abo->placement.num_placement; i++) {
- /* Try to move the BO into visible VRAM */
- if ((abo->placements[i].flags & TTM_PL_FLAG_VRAM) &&
- (!abo->placements[i].lpfn ||
- abo->placements[i].lpfn > lpfn))
- abo->placements[i].lpfn = lpfn;
- }
- abo->placement.busy_placement = abo->placement.placement;
- abo->placement.num_busy_placement = abo->placement.num_placement;
r = ttm_bo_validate(bo, &abo->placement, false, false);
if (unlikely(r != 0))
return r;
@@ -1057,3 +1048,34 @@ u64 amdgpu_bo_gpu_offset(struct amdgpu_bo *bo)
return bo->tbo.offset;
}
+
+/**
+ * amdgpu_bo_clear_cpu_access_required
+ * @bo: BO to update
+ *
+ * Clears CPU_ACCESS_REQUIRED flag if the BO hasn't had a page fault in a while
+ * and it didn't have a page fault too soon after the last time it was moved to
+ * VRAM.
+ *
+ * Caller should have bo reserved.
+ *
+ */
+void amdgpu_bo_clear_cpu_access_required(struct amdgpu_bo *bo)
+{
+ const unsigned int page_fault_timeout_ms = 10000;
+ const unsigned int min_period_ms = 500;
+ unsigned int ms_since_pf, period_ms;
+
+ ms_since_pf = jiffies_to_msecs(jiffies - bo->last_page_fault_jiffies);
+ period_ms = jiffies_to_msecs(abs(bo->last_page_fault_jiffies -
+ bo->last_cs_move_jiffies));
+
+ /*
+ * Try to avoid a revolving door between GTT and VRAM. Clearing the
+ * flag may move this BO back to VRAM, so don't clear it if it's likely
+ * to page fault and go right back to GTT.
+ */
+ if ((!bo->last_page_fault_jiffies || !bo->last_cs_move_jiffies) ||
+ (ms_since_pf > page_fault_timeout_ms && period_ms > min_period_ms))
+ bo->flags &= ~AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED;
+}
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
index 3824851..b0cb137 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
@@ -182,6 +182,7 @@ int amdgpu_bo_restore_from_shadow(struct amdgpu_device *adev,
struct reservation_object *resv,
struct dma_fence **fence,
bool direct);
+void amdgpu_bo_clear_cpu_access_required(struct amdgpu_bo *bo);
/*
--
2.7.4
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