Re: [PATCH] drm/ttm: Merge hugepage attr changes in ttm_dma_page_put.

["Zhang, Jerry (Junwei)" <Jerry.Zhang-5C7GfCeVMHo@public.gmane.org>]

On 07/26/2018 04:29 AM, Bas Nieuwenhuizen wrote:
> Every set_pages_array_wb call resulted in cross-core
> interrupts and TLB flushes. Merge more of them for
> less overhead.
>
> This reduces the time needed to free a 1.6 GiB GTT WC
> buffer as part of Vulkan CTS from  ~2 sec to < 0.25 sec.
> (Allocation still takes more than 2 sec though)
>
> Signed-off-by: Bas Nieuwenhuizen <basni@chromium.org>
> ---
>   drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 31 ++++++++++++++++++------
>   1 file changed, 24 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> index 4c659405a008a..9440ba0a55116 100644
> --- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> +++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> @@ -299,6 +299,25 @@ static int set_pages_array_uc(struct page **pages, int addrinarray)
>   #endif
>   	return 0;
>   }
> +
> +static int ttm_set_page_range_wb(struct page *p, unsigned long numpages)
> +{
> +#if IS_ENABLED(CONFIG_AGP)
> +        unsigned long i;
> +
> +        for (i = 0; i < numpages; i++)
> +                unmap_page_from_agp(p + i);
> +#endif
> +	return 0;
> +}
> +
> +#else /* for !CONFIG_X86 */
> +
> +static int ttm_set_page_range_wb(struct page *p, unsigned long numpages)
> +{
> +	return set_memory_wb((unsigned long)page_address(p), numpages);
> +}
> +
>   #endif /* for !CONFIG_X86 */
>
>   static int ttm_set_pages_caching(struct dma_pool *pool,
> @@ -387,18 +406,16 @@ static void ttm_pool_update_free_locked(struct dma_pool *pool,
>   static void ttm_dma_page_put(struct dma_pool *pool, struct dma_page *d_page)
>   {
>   	struct page *page = d_page->p;
> -	unsigned i, num_pages;
> +	unsigned num_pages;
>   	int ret;
>
>   	/* Don't set WB on WB page pool. */
>   	if (!(pool->type & IS_CACHED)) {
>   		num_pages = pool->size / PAGE_SIZE;
> -		for (i = 0; i < num_pages; ++i, ++page) {
> -			ret = set_pages_array_wb(&page, 1);
> -			if (ret) {
> -				pr_err("%s: Failed to set %d pages to wb!\n",
> -				       pool->dev_name, 1);
> -			}
> +		ret = ttm_set_page_range_wb(page, num_pages);

For AGP enabled, set_pages_array_wc() could works like that by passing "num_pages" instead of "1"
In X86 case, we may use set_pages_array_wb() in arch/x86/mm/pageattr.c.

so, does it work as below?

ret = set_pages_array_wb(page, num_pages);

Jerry

> +		if (ret) {
> +			pr_err("%s: Failed to set %d pages to wb!\n",
> +			       pool->dev_name, num_pages);
>   		}
>   	}
>
>
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