[PATCH v2] drm/amdgpu: Modify the contiguous flags behaviour
Paneer Selvam, Arunpravin
arunpravin.paneerselvam at amd.com
Wed Apr 17 13:27:46 UTC 2024
Hi Christian,
On 4/17/2024 12:19 PM, Christian König wrote:
> Am 17.04.24 um 08:21 schrieb Arunpravin Paneer Selvam:
>> 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.
>>
>> When we set AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS
>> - This means contiguous is not mandatory.
>> - 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.
>>
>> v2:
>> - keep the mem_flags and bo->flags check as is(Christian)
>> - place the TTM_PL_FLAG_CONTIGUOUS flag setting into the
>> amdgpu_bo_pin_restricted function placement range iteration
>> loop(Christian)
>> - rename find_pages with amdgpu_vram_mgr_calculate_pages_per_block
>> (Christian)
>> - Keep the kernel BO allocation as is(Christain)
>> - If BO pin vram allocation failed, we need to return -ENOSPC as
>> RDMA cannot work with scattered VRAM pages(Philip)
>>
>> 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 | 8 ++-
>> drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 57 +++++++++++++++-----
>> 2 files changed, 50 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>> index 8bc79924d171..caaef7b1df49 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>> @@ -153,8 +153,10 @@ 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)
>> + if (abo->tbo.type == ttm_bo_type_kernel &&
>> + flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS)
>> places[c].flags |= TTM_PL_FLAG_CONTIGUOUS;
>> +
>> c++;
>> }
>> @@ -966,6 +968,10 @@ int amdgpu_bo_pin_restricted(struct amdgpu_bo
>> *bo, u32 domain,
>> if (!bo->placements[i].lpfn ||
>> (lpfn && lpfn < bo->placements[i].lpfn))
>> bo->placements[i].lpfn = lpfn;
>> +
>> + if (bo->flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS &&
>> + bo->placements[i].mem_type == TTM_PL_VRAM)
>> + bo->placements[i].flags |= TTM_PL_FLAG_CONTIGUOUS;
>> }
>> r = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
>
> Nice work, up till here that looks exactly right as far as I can see.
>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>> index 8db880244324..4be8b091099a 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
>> @@ -88,6 +88,29 @@ static inline u64
>> amdgpu_vram_mgr_blocks_size(struct list_head *head)
>> return size;
>> }
>> +static inline unsigned long
>> +amdgpu_vram_mgr_calculate_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) {
>> + pages_per_block = ~0ul;
>
> If I understand it correctly this here enforces the allocation of a
> contiguous buffer in the way that it says we should have only one
> giant page for the whole BO.
yes, for contiguous we don't have the 2MB limit, hence we are setting to
maximum to avoid restricting the min_block_size to 2MB limitation.
>
>> + } 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 +474,10 @@ 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 +493,9 @@ 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_mgr_calculate_pages_per_block(tbo, place,
>> + bo_flags);
>> vres = kzalloc(sizeof(*vres), GFP_KERNEL);
>> if (!vres)
>> @@ -498,7 +514,7 @@ 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)
>> vres->flags |= DRM_BUDDY_CONTIGUOUS_ALLOCATION;
>
> And this here just optimizes it in the way that it says try harder to
> make it look contiguous.
Here I removed the TTM_PL_FLAG_CONTIGUOUS. AFAIU, in both cases (BO
pinning and normal contiguous request)
this flag AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS is always set.
>
> Question is if that also works with pages_per_block of 2MiB or does
> that only kick in when pages_per_block is maximal?
AFAIU, if this flag AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS is set, we are
setting the pages_per_block as maximal, thus
we dont limit the BO. when we set the pages_per_block as maximal, the
min_block_size would be the tbo->page_alignment,
and this tbo->page_alignment would be the same value as the required
size. Required size can be less than 2MB or more than 2MB.
Below we have check size >= pages_per_block, when the pages_per_block is
maximal we don't limit the min_block_size.
>
>> if (fpfn || lpfn != mgr->mm.size)
>> @@ -529,8 +545,21 @@ 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 (bo_flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS &&
>> + !(place->flags & TTM_PL_FLAG_CONTIGUOUS)) {
>> + /* Fallback to non contiguous allocation */
>> + vres->flags &= ~DRM_BUDDY_CONTIGUOUS_ALLOCATION;
>> + bo_flags &= ~AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS;
>
> Well I would say that this is a rather hacky implementation and should
> be avoided if possible.
sure, I will try to rewrite the code.
>
>> +
>> + pages_per_block =
>> + amdgpu_vram_mgr_calculate_pages_per_block(tbo,
>> + place,
>> + bo_flags);
>
> Rather move the AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS handling out of
> amdgpu_vram_mgr_calculate_pages_per_block().
sure.
Thanks,
Arun.
>
> Regards,
> Christian.
>
>> + continue;
>> + }
>> goto error_free_blocks;
>> + }
>> if (size > remaining_size)
>> remaining_size = 0;
>
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