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net: skbuff: avoid accessing page_pool if !napi_safe when returning page

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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>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Link: https://lore.kernel.org/r/20230804180529.2483231-5-aleksander.lobakin@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Alexander Lobakin 2023-08-04 20:05:27 +02:00 committed by Jakub Kicinski
parent 06d0fbdad6
commit 5b899c33b3
1 changed files with 7 additions and 5 deletions
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12
net/core/skbuff.c
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@ -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.