On Wed, Nov 28, 2012 at 10:05 AM, <j.glisse@xxxxxxxxx> wrote:
> From: Jerome Glisse <jglisse@xxxxxxxxxx>
>
> It make no sense to preserve caching state especialy when
> moving from vram to system. It burden the page allocator to
> match the vram caching (often WC) which just burn CPU cycle
> for no good reasons.
>
> Signed-off-by: Jerome Glisse <jglisse@xxxxxxxxxx>
> ---
> drivers/gpu/drm/ttm/ttm_bo.c | 15 +++------------
> 1 file changed, 3 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index bf6e4b5..39dcc58 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -896,19 +896,12 @@ static int ttm_bo_mem_force_space(struct ttm_buffer_object *bo,
> }
>
> static uint32_t ttm_bo_select_caching(struct ttm_mem_type_manager *man,
> - uint32_t cur_placement,
> uint32_t proposed_placement)
> {
> uint32_t caching = proposed_placement & TTM_PL_MASK_CACHING;
> uint32_t result = proposed_placement & ~TTM_PL_MASK_CACHING;
>
> - /**
> - * Keep current caching if possible.
> - */
> -
> - if ((cur_placement & caching) != 0)
> - result |= (cur_placement & caching);
> - else if ((man->default_caching & caching) != 0)
> + if ((man->default_caching & caching) != 0)
> result |= man->default_caching;
> else if ((TTM_PL_FLAG_CACHED & caching) != 0)
> result |= TTM_PL_FLAG_CACHED;
> @@ -978,8 +971,7 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
> if (!type_ok)
> continue;
>
> - cur_flags = ttm_bo_select_caching(man, bo->mem.placement,
> - cur_flags);
> + cur_flags = ttm_bo_select_caching(man, cur_flags);
> /*
> * Use the access and other non-mapping-related flag bits from
> * the memory placement flags to the current flags
> @@ -1023,8 +1015,7 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
> &cur_flags))
> continue;
>
> - cur_flags = ttm_bo_select_caching(man, bo->mem.placement,
> - cur_flags);
> + cur_flags = ttm_bo_select_caching(man, cur_flags);
> /*
> * Use the access and other non-mapping-related flag bits from
> * the memory placement flags to the current flags
> --
> 1.7.11.7
>
Note this is mostly to mitigate performance decrease when a lot of
eviction happen. It increase perf by as much of 60% on my computer.
Cheers,
Jerome
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