Re: [PATCH v6 net-nex 2/5] net: page_pool: add bulk support for ptr_ring

[Ilias Apalodimas <ilias.apalodimas@linaro.org>]

On Fri, Nov 13, 2020 at 12:48:29PM +0100, Lorenzo Bianconi wrote:
> Introduce the capability to batch page_pool ptr_ring refill since it is
> usually run inside the driver NAPI tx completion loop.
> 
> Suggested-by: Jesper Dangaard Brouer <brouer@redhat.com>
> Co-developed-by: Jesper Dangaard Brouer <brouer@redhat.com>
> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> ---
>  include/net/page_pool.h | 26 +++++++++++++++
>  net/core/page_pool.c    | 70 +++++++++++++++++++++++++++++++++++------
>  net/core/xdp.c          |  9 ++----
>  3 files changed, 88 insertions(+), 17 deletions(-)
> 
> diff --git a/include/net/page_pool.h b/include/net/page_pool.h
> index 81d7773f96cd..b5b195305346 100644
> --- a/include/net/page_pool.h
> +++ b/include/net/page_pool.h
> @@ -152,6 +152,8 @@ struct page_pool *page_pool_create(const struct page_pool_params *params);
>  void page_pool_destroy(struct page_pool *pool);
>  void page_pool_use_xdp_mem(struct page_pool *pool, void (*disconnect)(void *));
>  void page_pool_release_page(struct page_pool *pool, struct page *page);
> +void page_pool_put_page_bulk(struct page_pool *pool, void **data,
> +			     int count);
>  #else
>  static inline void page_pool_destroy(struct page_pool *pool)
>  {
> @@ -165,6 +167,11 @@ static inline void page_pool_release_page(struct page_pool *pool,
>  					  struct page *page)
>  {
>  }
> +
> +static inline void page_pool_put_page_bulk(struct page_pool *pool, void **data,
> +					   int count)
> +{
> +}
>  #endif
>  
>  void page_pool_put_page(struct page_pool *pool, struct page *page,
> @@ -215,4 +222,23 @@ static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
>  	if (unlikely(pool->p.nid != new_nid))
>  		page_pool_update_nid(pool, new_nid);
>  }
> +
> +static inline void page_pool_ring_lock(struct page_pool *pool)
> +	__acquires(&pool->ring.producer_lock)
> +{
> +	if (in_serving_softirq())
> +		spin_lock(&pool->ring.producer_lock);
> +	else
> +		spin_lock_bh(&pool->ring.producer_lock);
> +}
> +
> +static inline void page_pool_ring_unlock(struct page_pool *pool)
> +	__releases(&pool->ring.producer_lock)
> +{
> +	if (in_serving_softirq())
> +		spin_unlock(&pool->ring.producer_lock);
> +	else
> +		spin_unlock_bh(&pool->ring.producer_lock);
> +}
> +
>  #endif /* _NET_PAGE_POOL_H */
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index ef98372facf6..f3c690b8c8e3 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -11,6 +11,8 @@
>  #include <linux/device.h>
>  
>  #include <net/page_pool.h>
> +#include <net/xdp.h>
> +
>  #include <linux/dma-direction.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/page-flags.h>
> @@ -362,8 +364,9 @@ static bool pool_page_reusable(struct page_pool *pool, struct page *page)
>   * If the page refcnt != 1, then the page will be returned to memory
>   * subsystem.
>   */
> -void page_pool_put_page(struct page_pool *pool, struct page *page,
> -			unsigned int dma_sync_size, bool allow_direct)
> +static __always_inline struct page *
> +__page_pool_put_page(struct page_pool *pool, struct page *page,
> +		     unsigned int dma_sync_size, bool allow_direct)
>  {
>  	/* This allocator is optimized for the XDP mode that uses
>  	 * one-frame-per-page, but have fallbacks that act like the
> @@ -379,15 +382,12 @@ void page_pool_put_page(struct page_pool *pool, struct page *page,
>  			page_pool_dma_sync_for_device(pool, page,
>  						      dma_sync_size);
>  
> -		if (allow_direct && in_serving_softirq())
> -			if (page_pool_recycle_in_cache(page, pool))
> -				return;
> +		if (allow_direct && in_serving_softirq() &&
> +		    page_pool_recycle_in_cache(page, pool))
> +			return NULL;
>  
> -		if (!page_pool_recycle_in_ring(pool, page)) {
> -			/* Cache full, fallback to free pages */
> -			page_pool_return_page(pool, page);
> -		}
> -		return;
> +		/* Page found as candidate for recycling */
> +		return page;
>  	}
>  	/* Fallback/non-XDP mode: API user have elevated refcnt.
>  	 *
> @@ -405,9 +405,59 @@ void page_pool_put_page(struct page_pool *pool, struct page *page,
>  	/* Do not replace this with page_pool_return_page() */
>  	page_pool_release_page(pool, page);
>  	put_page(page);
> +
> +	return NULL;
> +}
> +
> +void page_pool_put_page(struct page_pool *pool, struct page *page,
> +			unsigned int dma_sync_size, bool allow_direct)
> +{
> +	page = __page_pool_put_page(pool, page, dma_sync_size, allow_direct);
> +	if (page && !page_pool_recycle_in_ring(pool, page)) {
> +		/* Cache full, fallback to free pages */
> +		page_pool_return_page(pool, page);
> +	}
>  }
>  EXPORT_SYMBOL(page_pool_put_page);
>  
> +/* Caller must not use data area after call, as this function overwrites it */
> +void page_pool_put_page_bulk(struct page_pool *pool, void **data,
> +			     int count)
> +{
> +	int i, bulk_len = 0;
> +
> +	for (i = 0; i < count; i++) {
> +		struct page *page = virt_to_head_page(data[i]);
> +
> +		page = __page_pool_put_page(pool, page, -1, false);
> +		/* Approved for bulk recycling in ptr_ring cache */
> +		if (page)
> +			data[bulk_len++] = page;
> +	}
> +
> +	if (unlikely(!bulk_len))
> +		return;
> +
> +	/* Bulk producer into ptr_ring page_pool cache */
> +	page_pool_ring_lock(pool);
> +	for (i = 0; i < bulk_len; i++) {
> +		if (__ptr_ring_produce(&pool->ring, data[i]))
> +			break; /* ring full */
> +	}
> +	page_pool_ring_unlock(pool);
> +
> +	/* Hopefully all pages was return into ptr_ring */
> +	if (likely(i == bulk_len))
> +		return;
> +
> +	/* ptr_ring cache full, free remaining pages outside producer lock
> +	 * since put_page() with refcnt == 1 can be an expensive operation
> +	 */
> +	for (; i < bulk_len; i++)
> +		page_pool_return_page(pool, data[i]);
> +}
> +EXPORT_SYMBOL(page_pool_put_page_bulk);
> +
>  static void page_pool_empty_ring(struct page_pool *pool)
>  {
>  	struct page *page;
> diff --git a/net/core/xdp.c b/net/core/xdp.c
> index bbaee7fdd44f..3d330ebda893 100644
> --- a/net/core/xdp.c
> +++ b/net/core/xdp.c
> @@ -393,16 +393,11 @@ EXPORT_SYMBOL_GPL(xdp_return_frame_rx_napi);
>  void xdp_flush_frame_bulk(struct xdp_frame_bulk *bq)
>  {
>  	struct xdp_mem_allocator *xa = bq->xa;
> -	int i;
>  
> -	if (unlikely(!xa))
> +	if (unlikely(!xa || !bq->count))
>  		return;
>  
> -	for (i = 0; i < bq->count; i++) {
> -		struct page *page = virt_to_head_page(bq->q[i]);
> -
> -		page_pool_put_full_page(xa->page_pool, page, false);
> -	}
> +	page_pool_put_page_bulk(xa->page_pool, bq->q, bq->count);
>  	/* bq->xa is not cleared to save lookup, if mem.id same in next bulk */
>  	bq->count = 0;
>  }
> -- 
> 2.26.2
> 
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>