[PATCH 1/1] drm/amdgpu: Remove rounding from vram allocation path

[Felix Kuehling]

Am 2022-07-25 um 13:14 schrieb Daniel Phillips:
> Rounding up allocations in the allocation path caused test regressions,
> so now just round in the availability path.
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 11 +++++------
>   1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> index 043a808c88a3..014a594899fb 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> @@ -40,10 +40,10 @@
>   #define AMDGPU_USERPTR_RESTORE_DELAY_MS 1
>   
>   /*
> - * Align VRAM allocations to 2MB to avoid fragmentation caused by 4K allocations in the tail 2MB
> + * Align VRAM availability to 2MB to avoid fragmentation caused by 4K allocations in the tail 2MB
>    * BO chunk
>    */
> -#define VRAM_ALLOCATION_ALIGN (1 << 21)
> +#define VRAM_AVAILABLITY_ALIGN (1 << 21)
>   
>   /* Impose limit on how much memory KFD can use */
>   static struct {
> @@ -149,7 +149,7 @@ static int amdgpu_amdkfd_reserve_mem_limit(struct amdgpu_device *adev,
>   		 * to avoid fragmentation caused by 4K allocations in the tail
>   		 * 2M BO chunk.
>   		 */
> -		vram_needed = ALIGN(size, VRAM_ALLOCATION_ALIGN);
> +		vram_needed = size;
>   	} else if (alloc_flag & KFD_IOC_ALLOC_MEM_FLAGS_USERPTR) {
>   		system_mem_needed = size;
>   	} else if (!(alloc_flag &
> @@ -198,7 +198,7 @@ static void unreserve_mem_limit(struct amdgpu_device *adev,
>   		kfd_mem_limit.system_mem_used -= size;
>   		kfd_mem_limit.ttm_mem_used -= size;
>   	} else if (alloc_flag & KFD_IOC_ALLOC_MEM_FLAGS_VRAM) {
> -		adev->kfd.vram_used -= ALIGN(size, VRAM_ALLOCATION_ALIGN);
> +		adev->kfd.vram_used -= size;

To calculate the available size taking potential fragmentation into 
account, we still need to track the aligned VRAM usage somewhere (say 
adev->kfd.vram_used_aligned), and use that in 
amdgpu_amdkfd_get_available_memory instead of adev->kfd.vram_used.

Regards,
   Felix


>   	} else if (alloc_flag & KFD_IOC_ALLOC_MEM_FLAGS_USERPTR) {
>   		kfd_mem_limit.system_mem_used -= size;
>   	} else if (!(alloc_flag &
> @@ -1642,7 +1642,6 @@ size_t amdgpu_amdkfd_get_available_memory(struct amdgpu_device *adev)
>   	uint64_t reserved_for_pt =
>   		ESTIMATE_PT_SIZE(amdgpu_amdkfd_total_mem_size);
>   	size_t available;
> -
>   	spin_lock(&kfd_mem_limit.mem_limit_lock);
>   	available = adev->gmc.real_vram_size
>   		- adev->kfd.vram_used
> @@ -1650,7 +1649,7 @@ size_t amdgpu_amdkfd_get_available_memory(struct amdgpu_device *adev)
>   		- reserved_for_pt;
>   	spin_unlock(&kfd_mem_limit.mem_limit_lock);
>   
> -	return ALIGN_DOWN(available, VRAM_ALLOCATION_ALIGN);
> +	return ALIGN_DOWN(available, VRAM_AVAILABLITY_ALIGN);
>   }
>   
>   int amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu(