[PATCH 2/2] drm/ttm: improve uncached page deallocation.

[Alex Deucher]

On Thu, Jul 9, 2015 at 2:19 PM,  <j.glisse at gmail.com> wrote:
> From: Jérôme Glisse <jglisse at redhat.com>
>
> Calls to set_memory_wb() incure heavy TLB flush and IPI cost. To
> minimize those wait until pool grow beyond batch size before
> draining the pool.
>
> Signed-off-by: Jérôme Glisse <jglisse at redhat.com>
> Reviewed-by: Mario Kleiner <mario.kleiner.de at gmail.com>
> Reviewed-and-Tested-by: Michel Dänzer <michel at daenzer.net>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
> Cc: Thomas Hellstrom <thellstrom at vmware.com>

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

> ---
>  drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> index af23080..624d941 100644
> --- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> +++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> @@ -963,13 +963,13 @@ void ttm_dma_unpopulate(struct ttm_dma_tt *ttm_dma, struct device *dev)
>         } else {
>                 pool->npages_free += count;
>                 list_splice(&ttm_dma->pages_list, &pool->free_list);
> -               if (pool->npages_free > _manager->options.max_size) {
> +               /*
> +                * Wait to have at at least NUM_PAGES_TO_ALLOC number of pages
> +                * to free in order to minimize calls to set_memory_wb().
> +                */
> +               if (pool->npages_free >= (_manager->options.max_size +
> +                                         NUM_PAGES_TO_ALLOC))
>                         npages = pool->npages_free - _manager->options.max_size;
> -                       /* free at least NUM_PAGES_TO_ALLOC number of pages
> -                        * to reduce calls to set_memory_wb */
> -                       if (npages < NUM_PAGES_TO_ALLOC)
> -                               npages = NUM_PAGES_TO_ALLOC;
> -               }
>         }
>         spin_unlock_irqrestore(&pool->lock, irq_flags);
>
> --
> 1.8.3.1
>
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