linux-kernel - Re: [PATCH net-next 0/2] net: Use SMP threads for backlog NAPI (or optional).

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Message-ID: <20231007155957.aPo0ImuG@linutronix.de>
Date:   Sat, 7 Oct 2023 17:59:57 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Wander Lairson Costa <hawk@...nel.org>
Subject: Re: [PATCH net-next 0/2] net: Use SMP threads for backlog NAPI (or
 optional).

On 2023-10-04 15:46:09 [-0700], Jakub Kicinski wrote:
> On Fri, 29 Sep 2023 18:20:18 +0200 Sebastian Andrzej Siewior wrote:
> >    - Patch #2 has been removed. Removing the warning is still an option.
> > 
> >    - There are two patches in the series:
> >      - Patch #1 always creates backlog threads
> >      - Patch #2 creates the backlog threads if requested at boot time,
> >        mandatory on PREEMPT_RT.
> >      So it is either or and I wanted to show how both look like.
> > 
> >    - The kernel test robot reported a performance regression with
> >      loopback (stress-ng --udp X --udp-ops Y) against the RFC version.
> >      The regression is now avoided by using local-NAPI if backlog
> >      processing is requested on the local CPU.
> 
> Not what we asked for, and it doesn't apply.

Apologies if I misunderstood. You said to make it optional which I did
with the static key in the second patch of this series. The first patch
is indeed not what we talked about I just to show what it would look
like now that there is no "delay" for backlog-NAPI on the local CPU.

If the optional part is okay then I can repost only that patch against
current net-next.

Sebastian