netdev - Re: [PATCH net-next 2/4] net: gro: change skb_gro_network

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Message-ID: <f8711f5c4d6dfae9d7f4bf64fdde15feaee56494.camel@redhat.com>
Date: Mon, 04 Mar 2024 09:28:08 +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: Richard Gobert <richardbgobert@...il.com>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com
Subject: Re: [PATCH net-next 2/4] net: gro: change skb_gro_network_header()

On Fri, 2024-03-01 at 19:37 +0000, Eric Dumazet wrote:
> Change skb_gro_network_header() to accept a const sk_buff
> and to no longer check if frag0 is NULL or not.
> 
> This allows to remove skb_gro_frag0_invalidate()
> which is seen in profiles when header-split is enabled.

I have a few questions to help me understanding this patchset better:

skb_gro_frag0_invalidate() shows in profiles (for non napi_frags_skb
callers?) because it's called multiple times for each aggregate packet,
right? I guessed writing the same cacheline multiple times per-se
should not be too much expansive.

perf here did not allow me to easily observed the mentioned cost,
because the function is inlined in many different places, I'm wondering
how you noticed?

Thanks!

Paolo