linux-kernel - [RFC PATCH 0/2] softirq: Per vector threading

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Message-Id: <1515735354-19279-1-git-send-email-frederic@kernel.org>
Date:   Fri, 12 Jan 2018 06:35:52 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Levin Alexander <alexander.levin@...izon.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Dmitry Safonov <dima@...sta.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Eric Dumazet <edumazet@...gle.com>,
        Radu Rendec <rrendec@...sta.com>,
        Ingo Molnar <mingo@...nel.org>,
        Stanislaw Gruszka <sgruszka@...hat.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Rik van Riel <riel@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Miller <davem@...emloft.net>
Subject: [RFC PATCH 0/2] softirq: Per vector threading

So this is a first shot to implement what Linus suggested.
To summarize: when a softirq vector is stormed and needs more time than
what IRQ tail can offer, the whole softirq processing is offloaded to
ksoftirqd. But this has an impact on other softirq vectors that are
then subject to scheduler latencies.

So the softirqs time limits is now per vector and only the vectors that
get stormed are offloaded to a thread (workqueue).

This is in a very Proof of concept state. It doesn't even boot successfully
once in a while. So I'll do more debugging tomorrow (today in fact) but
you get the big picture.

It probably won't come free given the clock reads around softirq callbacks.

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
	softirq/poc

HEAD: 0e982634115283710d0801048e5a316def26f31d

Thanks,
	Frederic
---

Frederic Weisbecker (2):
      softirq: Account time and iteration stats per vector
      softirq: Per vector thread deferment

 kernel/softirq.c | 123 +++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 114 insertions(+), 9 deletions(-)