Commit 21664814 authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

net: use napi_skb_cache even in process context 



This is a followup of commit e20dfbad ("net: fix napi_consume_skb()
with alien skbs").

Now the per-cpu napi_skb_cache is populated from TX completion path,
we can make use of this cache, especially for cpus not used
from a driver NAPI poll (primary user of napi_cache).

We can use the napi_skb_cache only if current context is not from hard irq.

With this patch, I consistently reach 130 Mpps on my UDP tx stress test
and reduce SLUB spinlock contention to smaller values.

Note there is still some SLUB contention for skb->head allocations.

I had to tune /sys/kernel/slab/skbuff_small_head/cpu_partial
and /sys/kernel/slab/skbuff_small_head/min_partial depending
on the platform taxonomy.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarJason Xing <kerneljasonxing@gmail.com>
Tested-by: default avatarJason Xing <kerneljasonxing@gmail.com>
Reviewed-by: default avatarKuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20251116202717.1542829-4-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 294e6382

net/core/skbuff.c

+5 −0
Original line number Diff line number Diff line
@@ -666,7 +666,12 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, 
		skb = napi_skb_cache_get(true);

		if (unlikely(!skb))

			return NULL;

	} else if (!in_hardirq() && !irqs_disabled()) {

		local_bh_disable();

		skb = napi_skb_cache_get(false);

		local_bh_enable();

	}



	if (!skb) {

fallback:

		skb = kmem_cache_alloc_node(cache, gfp_mask & ~GFP_DMA, node);