netdev - Re: [PATCH net-next] net: Make gro complete function to return void

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Date: Tue, 30 May 2023 16:36:42 -0600
From: David Ahern <dsahern@...nel.org>
To: Jakub Kicinski <kuba@...nel.org>, Parav Pandit <parav@...dia.com>
Cc: Eric Dumazet <edumazet@...gle.com>, davem@...emloft.net,
 pabeni@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: Make gro complete function to return void

On 5/30/23 1:39 PM, Jakub Kicinski wrote:
> On Tue, 30 May 2023 17:48:22 +0200 Eric Dumazet wrote:
>>> tcp_gro_complete seems fairly trivial. Any reason not to make it an
>>> inline and avoid another function call in the datapath?  
>>
>> Probably, although it is a regular function call, not an indirect one.
>>
>> In the grand total of driver rx napi + GRO cost, saving a few cycles
>> per GRO completed packet is quite small.
> 
> IOW please make sure you include the performance analysis quantifying
> the win, if you want to make this a static inline. Or let us know if
> the patch is good as is, I'm keeping it in pw for now.

I am not suggesting holding up this patch; just constantly looking for
these little savings here and there to keep lowering the overhead.

100G, 1500 MTU, line rate is 8.3M pps so GRO wise that would be ~180k
fewer function calls.