Merge branch 'page_pool-allow-caching-from-safely-localized-napi'

Jakub Kicinski says:

====================
page_pool: allow caching from safely localized NAPI

I went back to the explicit "are we in NAPI method", mostly
because I don't like having both around :( (even tho I maintain
that in_softirq() && !in_hardirq() is as safe, as softirqs do
not nest).

Still returning the skbs to a CPU, tho, not to the NAPI instance.
I reckon we could create a small refcounted struct per NAPI instance
which would allow sockets and other users so hold a persisent
and safe reference. But that's a bigger change, and I get 90+%
recycling thru the cache with just these patches (for RR and
streaming tests with 100% CPU use it's almost 100%).

Some numbers for streaming test with 100% CPU use (from previous version,
but really they perform the same):

		HW-GRO				page=page
		before		after		before		after
recycle:
cached:			0	138669686		0	150197505
cache_full:		0	   223391		0	    74582
ring:		138551933         9997191	149299454		0
ring_full: 		0             488	     3154	   127590
released_refcnt:	0		0		0		0

alloc:
fast:		136491361	148615710	146969587	150322859
slow:		     1772	     1799	      144	      105
slow_high_order:	0		0		0		0
empty:		     1772	     1799	      144	      105
refill:		  2165245	   156302	  2332880	     2128
waive:			0		0		0		0

v1: https://lore.kernel.org/all/20230411201800.596103-1-kuba@kernel.org/
rfcv2: https://lore.kernel.org/all/20230405232100.103392-1-kuba@kernel.org/
====================

Link: https://lore.kernel.org/r/20230413042605.895677-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 18 insertions, 8 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 96d27d558b0c..203c0df2046c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -360,8 +360,11 @@ struct napi_struct {
 	unsigned long		gro_bitmask;
 	int			(*poll)(struct napi_struct *, int);
 #ifdef CONFIG_NETPOLL
+	/* CPU actively polling if netpoll is configured */
 	int			poll_owner;
 #endif
+	/* CPU on which NAPI has been scheduled for processing */
+	int			list_owner;
 	struct net_device	*dev;
 	struct gro_list		gro_hash[GRO_HASH_BUCKETS];
 	struct sk_buff		*skb;
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 494a23a976b0..a823ec3aa326 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3386,6 +3386,18 @@ static inline void skb_frag_ref(struct sk_buff *skb, int f)
 	__skb_frag_ref(&skb_shinfo(skb)->frags[f]);
 }
 
+static inline void
+napi_frag_unref(skb_frag_t *frag, bool recycle, bool napi_safe)
+{
+	struct page *page = skb_frag_page(frag);
+
+#ifdef CONFIG_PAGE_POOL
+	if (recycle && page_pool_return_skb_page(page, napi_safe))
+		return;
+#endif
+	put_page(page);
+}
+
 /**
  * __skb_frag_unref - release a reference on a paged fragment.
  * @frag: the paged fragment
@@ -3396,13 +3408,7 @@ static inline void skb_frag_ref(struct sk_buff *skb, int f)
  */
 static inline void __skb_frag_unref(skb_frag_t *frag, bool recycle)
 {
-	struct page *page = skb_frag_page(frag);
-
-#ifdef CONFIG_PAGE_POOL
-	if (recycle && page_pool_return_skb_page(page))
-		return;
-#endif
-	put_page(page);
+	napi_frag_unref(frag, recycle, false);
 }
 
 /**
diff --git a/include/net/page_pool.h b/include/net/page_pool.h
index ddfa0b328677..91b808dade82 100644
--- a/include/net/page_pool.h
+++ b/include/net/page_pool.h
@@ -77,6 +77,7 @@ struct page_pool_params {
 	unsigned int	pool_size;
 	int		nid;  /* Numa node id to allocate from pages from */
 	struct device	*dev; /* device, for DMA pre-mapping purposes */
+	struct napi_struct *napi; /* Sole consumer of pages, otherwise NULL */
 	enum dma_data_direction dma_dir; /* DMA mapping direction */
 	unsigned int	max_len; /* max DMA sync memory size */
 	unsigned int	offset;  /* DMA addr offset */
@@ -239,7 +240,7 @@ inline enum dma_data_direction page_pool_get_dma_dir(struct page_pool *pool)
 	return pool->p.dma_dir;
 }
 
-bool page_pool_return_skb_page(struct page *page);
+bool page_pool_return_skb_page(struct page *page, bool napi_safe);
 
 struct page_pool *page_pool_create(const struct page_pool_params *params);