linux-kernel - Re: [RFC PATCH 1/4] softirq: Limit vector to a single iteration on IRQ tail

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Date:   Fri, 19 Jan 2018 10:25:03 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     David Miller <davem@...emloft.net>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sasha Levin <alexander.levin@...izon.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Dmitry Safonov <dima@...sta.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Radu Rendec <rrendec@...sta.com>,
        Ingo Molnar <mingo@...nel.org>,
        Stanislaw Gruszka <sgruszka@...hat.com>,
        Rik van Riel <riel@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [RFC PATCH 1/4] softirq: Limit vector to a single iteration on
 IRQ tail

On Fri, Jan 19, 2018 at 8:16 AM, David Miller <davem@...emloft.net> wrote:
>
> So this "get requeued" condition I think will trigger always for
> networking tunnel decapsulation.

Hmm. Interesting and a perhaps bit discouraging.

Will it always be just a _single_ level of indirection, or will double
tunnels (I assume some people do that, just because the universe is
out to get us) then result in this perhaps repeating several times?

Because it would be not very complicated to just have two bitmasks
(and still no per-softirq counting), and have that "switch to
threading only on the _second_ time this happens".

But let's have people test the behavior of this simpler model first?

                      Linus