linux-kernel - Re: Softirq priority inversion from "softirq: reduce latencies"

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Date:	Mon, 29 Feb 2016 08:24:23 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Mike Galbraith <umgwanakikbuti@...il.com>,
	Francois Romieu <romieu@...zoreil.com>,
	Eric Dumazet <edumazet@...gle.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
	dmaengine@...r.kernel.org, John Ogness <john.ogness@...utronix.de>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Softirq priority inversion from "softirq: reduce latencies"

On lun., 2016-02-29 at 07:58 -0800, Peter Hurley wrote:

> All that's happened is the first loop of NET_RX softirq has woken a
> process; that is sufficient to abort softirq and defer it for ksoftirqd.
> 
> That's why I'm saying this is a priority inversion, and one that
> will happen a lot.

Sure. This will happen every time ksoftirqd is launched.

Get rid of ksoftirqd or renice it so that you can easily be killed by
softirq storm.