netdev - Re: [PATCH v2 net-next 3/3] net: use napi_skb

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Message-ID: <74e58481-91fc-470e-9e5d-959289c8ab2c@redhat.com>
Date: Mon, 17 Nov 2025 11:12:21 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Eric Dumazet <edumazet@...gle.com>, "David S . Miller"
 <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>,
 Jason Xing <kerneljasonxing@...il.com>, netdev@...r.kernel.org,
 eric.dumazet@...il.com
Subject: Re: [PATCH v2 net-next 3/3] net: use napi_skb_cache even in process
 context

On 11/14/25 1:12 PM, Eric Dumazet wrote:
> This is a followup of commit e20dfbad8aab ("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.

Double checking I read the above correctly: you did the tune to reduce
the SLUB contention on skb->head and reach the 130Mpps target, am I correct?

If so, could you please share the used values for future memory?

Thanks!

Paolo