linux-kernel - Re: [RFC PATCH 2/4] softirq: Per vector deferment to workqueue

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Message-Id: <20180208.134506.1374787894560277876.davem@davemloft.net>
Date:   Thu, 08 Feb 2018 13:45:06 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     bigeasy@...utronix.de
Cc:     frederic@...nel.org, linux-kernel@...r.kernel.org,
        alexander.levin@...izon.com, peterz@...radead.org,
        mchehab@...pensource.com, torvalds@...ux-foundation.org,
        hannes@...essinduktion.org, paulmck@...ux.vnet.ibm.com,
        wanpeng.li@...mail.com, dima@...sta.com, tglx@...utronix.de,
        akpm@...ux-foundation.org, pabeni@...hat.com, rrendec@...sta.com,
        mingo@...nel.org, sgruszka@...hat.com, riel@...hat.com,
        edumazet@...gle.com
Subject: Re: [RFC PATCH 2/4] softirq: Per vector deferment to workqueue

From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Date: Thu, 8 Feb 2018 18:44:52 +0100

> May I instead suggest to stick to ksoftirqd? So you run in softirq
> context (after return from IRQ) and if takes too long, you offload the
> vector to ksoftirqd instead. You may want to play with the metric on
> which you decide when you want switch to ksoftirqd / account how long a
> vector runs.

Having read over this stuff for the past few weeks this is how I feel
as well.  Just make ksofbitrq do what we want (only execute the
overloaded softirq vectors).

The more I look at the workqueue stuff, the more complications and
weird behavioral artifacts we are getting for questionable gain.