[PATCH] drm/amdgpu: revert "use more than 64KB fragment size if possible"

[Deucher, Alexander]

> -----Original Message-----
> From: amd-gfx [mailto:amd-gfx-bounces at lists.freedesktop.org] On Behalf
> Of Christian König
> Sent: Tuesday, October 04, 2016 7:40 AM
> To: amd-gfx at lists.freedesktop.org
> Subject: [PATCH] drm/amdgpu: revert "use more than 64KB fragment size if
> possible"
> 
> From: Christian König <christian.koenig at amd.com>
> 
> This reverts commit 1dcd32fb9c54334ec948a0f18174a748d6b14364.
> 
> The block size is indeed an equal match, so this can cause performance
> regressions.
> 
> Signed-off-by: Christian König <christian.koenig at amd.com>

Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index 5d9b108..f4b78b6 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -882,13 +882,13 @@ static void amdgpu_vm_frag_ptes(struct
> amdgpu_pte_update_params	*params,
>  	 * allocation size to the fragment size.
>  	 */
> 
> -	const uint64_t frag_align = 1 << AMDGPU_LOG2_PAGES_PER_FRAG;
> +	/* SI and newer are optimized for 64KB */
> +	uint64_t frag_flags =
> AMDGPU_PTE_FRAG(AMDGPU_LOG2_PAGES_PER_FRAG);
> +	uint64_t frag_align = 1 << AMDGPU_LOG2_PAGES_PER_FRAG;
> 
>  	uint64_t frag_start = ALIGN(start, frag_align);
>  	uint64_t frag_end = end & ~(frag_align - 1);
> 
> -	uint32_t frag;
> -
>  	/* system pages are non continuously */
>  	if (params->src || !(flags & AMDGPU_PTE_VALID) ||
>  	    (frag_start >= frag_end)) {
> @@ -897,10 +897,6 @@ static void amdgpu_vm_frag_ptes(struct
> amdgpu_pte_update_params	*params,
>  		return;
>  	}
> 
> -	/* use more than 64KB fragment size if possible */
> -	frag = lower_32_bits(frag_start | frag_end);
> -	frag = likely(frag) ? __ffs(frag) : 31;
> -
>  	/* handle the 4K area at the beginning */
>  	if (start != frag_start) {
>  		amdgpu_vm_update_ptes(params, vm, start, frag_start,
> @@ -910,7 +906,7 @@ static void amdgpu_vm_frag_ptes(struct
> amdgpu_pte_update_params	*params,
> 
>  	/* handle the area in the middle */
>  	amdgpu_vm_update_ptes(params, vm, frag_start, frag_end, dst,
> -			      flags | AMDGPU_PTE_FRAG(frag));
> +			      flags | frag_flags);
> 
>  	/* handle the 4K area at the end */
>  	if (frag_end != end) {
> --
> 2.5.0
> 
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