netdev - Re: [PATCH net-next] tcp: gro: inline tcp_gro_pull

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Message-ID: <a9d3ac94-e418-4e5f-a3f1-5cc05cb7c865@intel.com>
Date: Fri, 14 Nov 2025 17:37:58 +0100
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Eric Dumazet <edumazet@...gle.com>
CC: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Simon Horman
	<horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>,
	<netdev@...r.kernel.org>, <eric.dumazet@...il.com>
Subject: Re: [PATCH net-next] tcp: gro: inline tcp_gro_pull_header()

From: Eric Dumazet <edumazet@...gle.com>
Date: Fri, 14 Nov 2025 08:09:31 -0800

> On Fri, Nov 14, 2025 at 7:56 AM Alexander Lobakin
> <aleksander.lobakin@...el.com> wrote:
>>
>> From: Eric Dumazet <edumazet@...gle.com>
>> Date: Thu, 13 Nov 2025 14:03:57 +0000
>>
>>> tcp_gro_pull_header() is used in GRO fast path, inline it.
>>
>> Looks reasonable, but... any perf numbers? bloat-o-meter stats?
> 
> This is used two times, one from IPv4, one from IPv6.
> 
> FDO usually embeds this function in the two callers, this patch
> reduces the gap between FDO and non FDO kernels.
> Non FDO builds get a ~0.5 % performance increase with this patch, for
> a cost of less than 192 bytes on x86_64.

I asked for these as you usually provide detailed stats with `perf top`
output etc, but not this time.

(although you always require to provide perf stats when someone else
 sends an optimization patch)

> 
> It might sound small, but adding all these changes together is not small.

A couple weeks ago you wrote that 1% of perf improvement is "a noise".

I'm not against this patch (if you add everything from the above to the
commit message + maybe your usual detailed stats).
+0.5% for 192 bytes sounds good to me (I don't call it "a noise").

But from my PoV this just feels like "my 0.5% is bigger than your 1%"
and "you have to show me the numbers, and I don't".

The rules are the same for everyone.

Thanks,
Olek