[PATCH] drm/amdgpu: Modify the contiguous flags behaviour
Paneer Selvam, Arunpravin
arunpravin.paneerselvam at amd.com
Tue Apr 16 07:56:12 UTC 2024
Hi Christian,
On 4/16/2024 1:16 PM, Christian König wrote:
> Am 16.04.24 um 00:02 schrieb Philip Yang:
>> On 2024-04-14 10:57, Arunpravin Paneer Selvam wrote:
>>> Now we have two flags for contiguous VRAM buffer allocation.
>>> If the application request for AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS,
>>> it would set the ttm place TTM_PL_FLAG_CONTIGUOUS flag in the
>>> buffer's placement function.
>>>
>>> This patch will change the default behaviour of the two flags.
>> This change will simplify the KFD best effort contiguous VRAM
>> allocation, because KFD doesn't need set new GEM_ flag.
>>> When we set AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS
>>> - This means contiguous is not mandatory.
>>
>> AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS used in couple of places. For page
>> table BO, it is fine as BO size is page size 4K. For 64KB reserved
>> BOs and F/W size related BOs, do all allocation happen at driver
>> initialization before the VRAM is fragmented?
>>
>
> Oh, that's a really good point, we need to keep the behavior as is for
> kernel allocations. Arun can you take care of that?
Sure, I will take care kernel allocations.
Thanks,
Arun.
>
> Thanks,
> Christian.
>
>>> - we will try to allocate the contiguous buffer. Say if the
>>> allocation fails, we fallback to allocate the individual pages.
>>>
>>> When we setTTM_PL_FLAG_CONTIGUOUS
>>> - This means contiguous allocation is mandatory.
>>> - we are setting this in amdgpu_bo_pin_restricted() before bo
>>> validation
>>> and check this flag in the vram manager file.
>>> - if this is set, we should allocate the buffer pages contiguously.
>>> the allocation fails, we return -ENOSPC.
>>>
>>> Signed-off-by: Arunpravin Paneer
>>> Selvam<Arunpravin.PaneerSelvam at amd.com>
>>> Suggested-by: Christian König<christian.koenig at amd.com>
>>> ---
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 14 +++--
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 57
>>> +++++++++++++++-----
>>> 2 files changed, 49 insertions(+), 22 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>> index 8bc79924d171..41926d631563 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>> @@ -153,8 +153,6 @@ void amdgpu_bo_placement_from_domain(struct
>>> amdgpu_bo *abo, u32 domain)
>>> else
>>> places[c].flags |= TTM_PL_FLAG_TOPDOWN;
>>> - if (flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS)
>>> - places[c].flags |= TTM_PL_FLAG_CONTIGUOUS;
>>> c++;
>>> }
>>> @@ -899,6 +897,8 @@ int amdgpu_bo_pin_restricted(struct amdgpu_bo
>>> *bo, u32 domain,
>>> {
>>> struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
>>> struct ttm_operation_ctx ctx = { false, false };
>>> + struct ttm_place *places = bo->placements;
>>> + u32 c = 0;
>>> int r, i;
>>> if (amdgpu_ttm_tt_get_usermm(bo->tbo.ttm))
>>> @@ -921,16 +921,10 @@ int amdgpu_bo_pin_restricted(struct amdgpu_bo
>>> *bo, u32 domain,
>>> if (bo->tbo.pin_count) {
>>> uint32_t mem_type = bo->tbo.resource->mem_type;
>>> - uint32_t mem_flags = bo->tbo.resource->placement;
>>> if (!(domain & amdgpu_mem_type_to_domain(mem_type)))
>>> return -EINVAL;
>>> - if ((mem_type == TTM_PL_VRAM) &&
>>> - (bo->flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS) &&
>>> - !(mem_flags & TTM_PL_FLAG_CONTIGUOUS))
>>> - return -EINVAL;
>>> -
>> This looks like a bug before, but with this patch, the check makes
>> sense and is needed.
>>> ttm_bo_pin(&bo->tbo);
>>> if (max_offset != 0) {
>>> @@ -968,6 +962,10 @@ int amdgpu_bo_pin_restricted(struct amdgpu_bo
>>> *bo, u32 domain,
>>> bo->placements[i].lpfn = lpfn;
>>> }
>>> + if (domain & AMDGPU_GEM_DOMAIN_VRAM &&
>>> + !WARN_ON(places[c].mem_type != TTM_PL_VRAM))
>>> + places[c].flags |= TTM_PL_FLAG_CONTIGUOUS;
>>> +
>>
>> If BO pinned is not allocated with AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS,
>> should pin and return scattered pages because the RDMA support
>> scattered dmabuf. Christian also pointed this out.
>>
>> If (bo->flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS &&
>>
>> bo->placements[i].mem_type == TTM_PL_VRAM)
>> o->placements[i].flags |= TTM_PL_FLAG_CONTIGUOUS;
>>> r = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
>>> if (unlikely(r)) {
>>> dev_err(adev->dev, "%p pin failed\n", bo);
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>>> index 8db880244324..ddbf302878f6 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>>> @@ -88,6 +88,30 @@ static inline u64
>>> amdgpu_vram_mgr_blocks_size(struct list_head *head)
>>> return size;
>>> }
>>> +static inline unsigned long
>>> +amdgpu_vram_find_pages_per_block(struct ttm_buffer_object *tbo,
>>> + const struct ttm_place *place,
>>> + unsigned long bo_flags)
>>> +{
>>> + unsigned long pages_per_block;
>>> +
>>> + if (bo_flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS ||
>>> + place->flags & TTM_PL_FLAG_CONTIGUOUS) {
>>> + pages_per_block = ~0ul;
>>> + } else {
>>> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>>> + pages_per_block = HPAGE_PMD_NR;
>>> +#else
>>> + /* default to 2MB */
>>> + pages_per_block = 2UL << (20UL - PAGE_SHIFT);
>>> +#endif
>>> + pages_per_block = max_t(uint32_t, pages_per_block,
>>> + tbo->page_alignment);
>>> + }
>>> +
>>> + return pages_per_block;
>>> +}
>>> +
>>> /**
>>> * DOC: mem_info_vram_total
>>> *
>>> @@ -451,8 +475,10 @@ static int amdgpu_vram_mgr_new(struct
>>> ttm_resource_manager *man,
>>> struct amdgpu_vram_mgr *mgr = to_vram_mgr(man);
>>> struct amdgpu_device *adev = to_amdgpu_device(mgr);
>>> u64 vis_usage = 0, max_bytes, min_block_size;
>>> + struct amdgpu_bo *bo = ttm_to_amdgpu_bo(tbo);
>>> struct amdgpu_vram_mgr_resource *vres;
>>> u64 size, remaining_size, lpfn, fpfn;
>>> + unsigned long bo_flags = bo->flags;
>>> struct drm_buddy *mm = &mgr->mm;
>>> struct drm_buddy_block *block;
>>> unsigned long pages_per_block;
>>> @@ -468,18 +494,8 @@ static int amdgpu_vram_mgr_new(struct
>>> ttm_resource_manager *man,
>>> if (tbo->type != ttm_bo_type_kernel)
>>> max_bytes -= AMDGPU_VM_RESERVED_VRAM;
>>> - if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
>>> - pages_per_block = ~0ul;
>>> - } else {
>>> -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>>> - pages_per_block = HPAGE_PMD_NR;
>>> -#else
>>> - /* default to 2MB */
>>> - pages_per_block = 2UL << (20UL - PAGE_SHIFT);
>>> -#endif
>>> - pages_per_block = max_t(uint32_t, pages_per_block,
>>> - tbo->page_alignment);
>>> - }
>>> + pages_per_block =
>>> + amdgpu_vram_find_pages_per_block(tbo, place, bo_flags);
>>> vres = kzalloc(sizeof(*vres), GFP_KERNEL);
>>> if (!vres)
>>> @@ -498,7 +514,8 @@ static int amdgpu_vram_mgr_new(struct
>>> ttm_resource_manager *man,
>>> if (place->flags & TTM_PL_FLAG_TOPDOWN)
>>> vres->flags |= DRM_BUDDY_TOPDOWN_ALLOCATION;
>>> - if (place->flags & TTM_PL_FLAG_CONTIGUOUS)
>>> + if (bo_flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS ||
>>> + place->flags & TTM_PL_FLAG_CONTIGUOUS)
>>> vres->flags |= DRM_BUDDY_CONTIGUOUS_ALLOCATION;
>>> if (fpfn || lpfn != mgr->mm.size)
>>> @@ -529,8 +546,20 @@ static int amdgpu_vram_mgr_new(struct
>>> ttm_resource_manager *man,
>>> min_block_size,
>>> &vres->blocks,
>>> vres->flags);
>>> - if (unlikely(r))
>>> + if (unlikely(r)) {
>>
>> If pin BO failed to allocate contiguous VRAM, this should return
>> failure to application, as RDMA cannot work with scattered VRAM pages.
>>
>> Regards,
>>
>> Philip
>>
>>> + if (bo_flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS) {
>>> + /* Fallback to non contiguous allocation */
>>> + vres->flags &= ~DRM_BUDDY_CONTIGUOUS_ALLOCATION;
>>> + bo_flags &= ~AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS;
>>> +
>>> + pages_per_block =
>>> + amdgpu_vram_find_pages_per_block(tbo,
>>> + place,
>>> + bo_flags);
>>> + continue;
>>> + }
>>> goto error_free_blocks;
>>> + }
>>> if (size > remaining_size)
>>> remaining_size = 0;
>
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