netdev - Re: [PATCH v2 07/24] page_pool: Convert __page_pool_put_page() to __page_pool_put

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Message-ID: <Y700FlsBvAoBKkKv@hera>
Date:   Tue, 10 Jan 2023 11:47:02 +0200
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc:     Jesper Dangaard Brouer <hawk@...nel.org>, netdev@...r.kernel.org,
        linux-mm@...ck.org, Shakeel Butt <shakeelb@...gle.com>
Subject: Re: [PATCH v2 07/24] page_pool: Convert __page_pool_put_page() to
 __page_pool_put_netmem()

On Thu, Jan 05, 2023 at 09:46:14PM +0000, Matthew Wilcox (Oracle) wrote:
> Removes the call to compound_head() hidden in put_page() which
> saves 169 bytes of kernel text as __page_pool_put_page() is
> inlined twice.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> ---
>  net/core/page_pool.c | 29 +++++++++++++++++++----------
>  1 file changed, 19 insertions(+), 10 deletions(-)
>
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index b606952773a6..8f3f7cc5a2d5 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -558,8 +558,8 @@ static bool page_pool_recycle_in_cache(struct page *page,
>   * If the page refcnt != 1, then the page will be returned to memory
>   * subsystem.
>   */
> -static __always_inline struct page *
> -__page_pool_put_page(struct page_pool *pool, struct page *page,
> +static __always_inline struct netmem *
> +__page_pool_put_netmem(struct page_pool *pool, struct netmem *nmem,
>  		     unsigned int dma_sync_size, bool allow_direct)
>  {
>  	/* This allocator is optimized for the XDP mode that uses
> @@ -571,19 +571,20 @@ __page_pool_put_page(struct page_pool *pool, struct page *page,
>  	 * page is NOT reusable when allocated when system is under
>  	 * some pressure. (page_is_pfmemalloc)
>  	 */
> -	if (likely(page_ref_count(page) == 1 && !page_is_pfmemalloc(page))) {
> -		/* Read barrier done in page_ref_count / READ_ONCE */
> +	if (likely(netmem_ref_count(nmem) == 1 &&
> +		   !netmem_is_pfmemalloc(nmem))) {
> +		/* Read barrier done in netmem_ref_count / READ_ONCE */
>
>  		if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
> -			page_pool_dma_sync_for_device(pool, page,
> +			page_pool_dma_sync_for_device(pool, netmem_page(nmem),
>  						      dma_sync_size);
>
>  		if (allow_direct && in_serving_softirq() &&
> -		    page_pool_recycle_in_cache(page, pool))
> +		    page_pool_recycle_in_cache(netmem_page(nmem), pool))
>  			return NULL;
>
>  		/* Page found as candidate for recycling */
> -		return page;
> +		return nmem;
>  	}
>  	/* Fallback/non-XDP mode: API user have elevated refcnt.
>  	 *
> @@ -599,13 +600,21 @@ __page_pool_put_page(struct page_pool *pool, struct page *page,
>  	 * will be invoking put_page.
>  	 */
>  	recycle_stat_inc(pool, released_refcnt);
> -	/* Do not replace this with page_pool_return_page() */
> -	page_pool_release_page(pool, page);
> -	put_page(page);
> +	/* Do not replace this with page_pool_return_netmem() */
> +	page_pool_release_netmem(pool, nmem);
> +	netmem_put(nmem);
>
>  	return NULL;
>  }
>
> +static __always_inline struct page *
> +__page_pool_put_page(struct page_pool *pool, struct page *page,
> +		     unsigned int dma_sync_size, bool allow_direct)
> +{
> +	return netmem_page(__page_pool_put_netmem(pool, page_netmem(page),
> +						dma_sync_size, allow_direct));
> +}
> +
>  void page_pool_put_defragged_page(struct page_pool *pool, struct page *page,
>  				  unsigned int dma_sync_size, bool allow_direct)
>  {
> --
> 2.35.1
>

Reviewed-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>