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

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Jul 08, 2015 at 02:16:37PM -0400, j.glisse@gmail.com wrote:
> From: Jérôme Glisse <jglisse@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@redhat.com>
> Reviewed-by: Mario Kleiner <mario.kleiner.de@gmail.com>
> Cc: Michel Dänzer <michel@daenzer.net>
> Cc: Thomas Hellstrom <thellstrom@vmware.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
>  drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> index 0194a93..8028dd6 100644
> --- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> +++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> @@ -953,7 +953,12 @@ 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;
>  	}
>  	spin_unlock_irqrestore(&pool->lock, irq_flags);
> -- 
> 1.8.3.1
> 
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