diff mbox series

[net-next,v4,4/6] net: skbuff: avoid accessing page_pool if !napi_safe when returning page

Message ID 20230804180529.2483231-5-aleksander.lobakin@intel.com
State New
Headers
Series page_pool: a couple of assorted optimizations |

Commit Message

Alexander Lobakin Aug. 4, 2023, 6:05 p.m. UTC 
  Currently, pp->p.napi is always read, but the actual variable it gets
assigned to is read-only when @napi_safe is true. For the !napi_safe
cases, which yet is still a pack, it's an unneeded operation.
Moreover, it can lead to premature or even redundant page_pool
cacheline access. For example, when page_pool_is_last_frag() returns
false (with the recent frag improvements).
Thus, read it only when @napi_safe is true. This also allows moving
@napi inside the condition block itself. Constify it while we are
here, because why not.

Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 net/core/skbuff.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index acc5844a0de1..85f82a6a08dc 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -882,9 +882,8 @@  static void skb_clone_fraglist(struct sk_buff *skb)
 #if IS_ENABLED(CONFIG_PAGE_POOL)
 bool napi_pp_put_page(struct page *page, bool napi_safe)
 {
-	struct napi_struct *napi;
+	bool allow_direct = false;
 	struct page_pool *pp;
-	bool allow_direct;
 
 	page = compound_head(page);
 
@@ -904,9 +903,12 @@  bool napi_pp_put_page(struct page *page, bool napi_safe)
 	 * in the same context as the consumer would run, so there's
 	 * no possible race.
 	 */
-	napi = READ_ONCE(pp->p.napi);
-	allow_direct = napi_safe && napi &&
-		READ_ONCE(napi->list_owner) == smp_processor_id();
+	if (napi_safe) {
+		const struct napi_struct *napi = READ_ONCE(pp->p.napi);
+
+		allow_direct = napi &&
+			READ_ONCE(napi->list_owner) == smp_processor_id();
+	}
 
 	/* Driver set this to memory recycling info. Reset it on recycle.
 	 * This will *not* work for NIC using a split-page memory model.