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

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Date:   Thu, 11 Jan 2018 11:38:40 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     peterz@...radead.org
Cc:     edumazet@...gle.com, dima@...sta.com, frederic@...nel.org,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        0x7f454c46@...il.com, akpm@...ux-foundation.org,
        fweisbec@...il.com, hannes@...essinduktion.org, mingo@...nel.org,
        alexander.levin@...izon.com, pabeni@...hat.com,
        paulmck@...ux.vnet.ibm.com, rrendec@...sta.com, riel@...hat.com,
        sgruszka@...hat.com, tglx@...utronix.de, wanpeng.li@...mail.com
Subject: Re: [RFC 1/2] softirq: Defer net rx/tx processing to ksoftirqd
 context

From: Peter Zijlstra <peterz@...radead.org>
Date: Thu, 11 Jan 2018 17:32:04 +0100

> You just introduced a 2ms preempt-disable region I think, that's not
> cool for PREEMPT and a plain bug on PREEMPT_RT.

I'd just like to know what the difference is between ksoftirqd running
softirq work for 2ms and the real softirq context doing it.  The
latter already has this "2ms preempt-disable region" of sorts, right?