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net: save some cycles when doing skb_attempt_defer_free() 

Normally, we don't face these two exceptions very often meanwhile
we have some chance to meet the condition where the current cpu id
is the same as skb->alloc_cpu.

One simple test that can help us see the frequency of this statement
'cpu == raw_smp_processor_id()':
1. running iperf -s and iperf -c [ip] -P [MAX CPU]
2. using BPF to capture skb_attempt_defer_free()

I can see around 4% chance that happens to satisfy the statement.
So moving this statement at the beginning can save some cycles in
most cases.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jason Xing 2024-04-12 11:07:18 +08:00 committed by David S. Miller
parent 71329c4918
commit 4d0470b9ad
1 changed files with 3 additions and 3 deletions
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6
net/core/skbuff.c
View File

@ -6965,9 +6965,9 @@ void skb_attempt_defer_free(struct sk_buff *skb)
unsigned int defer_max;
bool kick;
if (WARN_ON_ONCE(cpu >= nr_cpu_ids) ||
!cpu_online(cpu) ||
cpu == raw_smp_processor_id()) {
if (cpu == raw_smp_processor_id() ||
WARN_ON_ONCE(cpu >= nr_cpu_ids) ||
!cpu_online(cpu)) {
nodefer: kfree_skb_napi_cache(skb);
return;
}