linux-kernel - Re: [RFC 1/2] softirq: Defer net rx/tx processing to ksoftirqd context

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Message-ID: <CA+55aFyZPzkjwkLXWWXp3KUfLD7MUtGxSu1Q6vc0O5i9Ea6ZKw@mail.gmail.com>
Date:   Thu, 11 Jan 2018 11:43:23 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Dmitry Safonov <dima@...sta.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Miller <davem@...emloft.net>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>,
        Paolo Abeni <pabeni@...hat.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Radu Rendec <rrendec@...sta.com>,
        Rik van Riel <riel@...hat.com>,
        Stanislaw Gruszka <sgruszka@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [RFC 1/2] softirq: Defer net rx/tx processing to ksoftirqd context

On Thu, Jan 11, 2018 at 11:15 AM, Eric Dumazet <edumazet@...gle.com> wrote:
>
> How are we supposed to know this particular workload is problematic
> for innocent user threads on the same cpu ?

Put that question another way: how is the _softirq_ code supposed to know?

If you can't know, then the softirq code definitely can't know either.
It has even less information. It doesn't know about NAPI, it doesn't
know about irq steering, it doesn't know anything at all.

               Linus