From 5b899c33b3b852b9559b724cfee67801324a0886 Mon Sep 17 00:00:00 2001 From: Alexander Lobakin Date: Fri, 4 Aug 2023 20:05:27 +0200 Subject: net: skbuff: avoid accessing page_pool if !napi_safe when returning page 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 Reviewed-by: Alexander Duyck Link: https://lore.kernel.org/r/20230804180529.2483231-5-aleksander.lobakin@intel.com Signed-off-by: Jakub Kicinski --- net/core/skbuff.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) (limited to 'net/core') 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. -- cgit v1.2.3