Hi Felix,
On 5/21/2023 12:09 AM, Felix Kuehling wrote:
Am 2023-05-20 um 05:25 schrieb Arunpravin Paneer Selvam:
This reverts commit c105518679b6e87232874ffc989ec403bee59664.
This patch disables the TOPDOWN flag for APU and few dGPU cards
which has the VRAM size equal to the BAR size.
With resizable BARs it's not that rare.
When we enable the TOPDOWN flag, we get the free blocks at
the highest available memory region and we don't split the
lower order blocks. This change is required to keep off
the fragmentation related issues particularly in ASIC
which has VRAM space <= 500MiB
If TOPDOWN has these general benefits, then would it make sense to
allocate visible memory TOPDOWN as well, on large-BAR GPUs? Without
knowing too much about the internals of the allocator, my intuition
tells me that using only one allocation strategy has a better chance
of minimizing fragmentation than mixing two allocation strategies for
no good reason.
We have 2 allocation strategies for visible memory and non-visible
memory. For visible memory we are going with tree based search as we
should limit our allocation within a specified range limit. The TOPDOWN
flag is not applicable for tree based
search allocation. For non-visible memory we pick free blocks from the
free list and here the TOPDOWN flag is applicable.
For large-BAR GPUs visible memory, we don't go with tree based search
since the BAR == VRAM size, and if this
AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED flag is set for every allocation
on large-BAR GPUs, we don't set TOPDOWN flag and
this could create fragmentation issue in case of heavy load. I will
check the behavior on large BAR GPUs and set the TOPDOWN flag if not set.
Thanks,
Arun.
Regards,
Felix
Hence, we are reverting this patch.
Gitlab issue link - https://gitlab.freedesktop.org/drm/amd/-/issues/2270
Signed-off-by: Arunpravin Paneer Selvam
<Arunpravin.PaneerSelvam@xxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
index 2bd1a54ee866..ca5fc07faf6c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
@@ -139,7 +139,7 @@ void amdgpu_bo_placement_from_domain(struct
amdgpu_bo *abo, u32 domain)
if (flags & AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED)
places[c].lpfn = visible_pfn;
- else if (adev->gmc.real_vram_size !=
adev->gmc.visible_vram_size)
+ else
places[c].flags |= TTM_PL_FLAG_TOPDOWN;
if (flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS)
