netdev - Re: [PATCH net-next] net: add prefetch() in skb_defer_free

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Message-ID: <8ef591e6-9b05-4c7b-8d75-82ced4dd2f31@redhat.com>
Date: Thu, 6 Nov 2025 10:05:13 +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>, netdev@...r.kernel.org,
 eric.dumazet@...il.com
Subject: Re: [PATCH net-next] net: add prefetch() in skb_defer_free_flush()

On 11/6/25 9:55 AM, Eric Dumazet wrote:
> skb_defer_free_flush() is becoming more important these days.
> 
> Add a prefetch operation to reduce latency a bit on some
> platforms like AMD EPYC 7B12.
> 
> On more recent cpus, a stall happens when reading skb_shinfo().
> Avoiding it will require a more elaborate strategy.

For my education, how do you catch such stalls? looking for specific
perf events? Or just based on cycles spent in a given function/chunk of
code?

> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Just to avoid doubts on my thoughts about this patch:

Acked-by: Paolo Abeni <pabeni@...hat.com>