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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Paolo Abeni <pabeni@redhat.com>
Cc: David Miller <davem@davemloft.net>,
	Frederic Weisbecker <frederic@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Sasha Levin <alexander.levin@verizon.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Mauro Carvalho Chehab <mchehab@s-opensource.com>,
	Hannes Frederic Sowa <hannes@stressinduktion.org>,
	Paul McKenney <paulmck@linux.vnet.ibm.com>,
	Wanpeng Li <wanpeng.li@hotmail.com>,
	Dmitry Safonov <dima@arista.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Radu Rendec <rrendec@arista.com>, Ingo Molnar <mingo@kernel.org>,
	Stanislaw Gruszka <sgruszka@redhat.com>,
	Rik van Riel <riel@redhat.com>,
	Eric Dumazet <edumazet@google.com>
Subject: Re: [RFC PATCH 0/4] softirq: Per vector threading v3
Date: Tue, 23 Jan 2018 09:42:32 -0800	[thread overview]
Message-ID: <CA+55aFwEMe=jV7pvV2dWFKrQ--mAw3buXhdJ-Qk2u-290rTQQQ@mail.gmail.com> (raw)
In-Reply-To: <1516726652.2554.58.camel@redhat.com>

On Tue, Jan 23, 2018 at 8:57 AM, Paolo Abeni <pabeni@redhat.com> wrote:
>
>> Or is it that the workqueue execution is simply not yielding for some
>> reason?
>
> It's like that.
>
> I spent little time on it, so I haven't many data point. I'll try to
> investigate the scenario later this week.

Hmm. workqueues seem to use cond_resched_rcu_qs(), which does a
cond_resched() (and a RCU quiescent note).

But I wonder if the test triggers the "lets run lots of workqueue
threads", and then the single-threaded user space just gets blown out
of the water by many kernel threads. Each thread gets its own "fair"
amount of CPU, but..

                   Linus

  reply	other threads:[~2018-01-23 17:42 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-19 15:46 [RFC PATCH 0/4] softirq: Per vector threading v3 Frederic Weisbecker
2018-01-19 15:46 ` [RFC PATCH 1/4] softirq: Limit vector to a single iteration on IRQ tail Frederic Weisbecker
2018-01-19 16:16   ` David Miller
2018-01-19 18:25     ` Linus Torvalds
2018-01-19 18:47       ` David Miller
2018-01-21 16:30         ` Frederic Weisbecker
2018-01-21 16:57           ` David Miller
2018-01-19 15:46 ` [RFC PATCH 2/4] softirq: Per vector deferment to workqueue Frederic Weisbecker
2018-01-20  8:41   ` Pavan Kondeti
2018-01-21 16:11     ` Frederic Weisbecker
2018-01-21 17:50       ` Pavan Kondeti
2018-01-21 20:48         ` Frederic Weisbecker
2018-02-08 17:44   ` Sebastian Andrzej Siewior
2018-02-08 18:45     ` David Miller
2018-02-08 20:14       ` Dmitry Safonov
2018-02-08 20:22         ` David Miller
2018-02-08 20:30           ` Dmitry Safonov
2018-02-09  4:11             ` Mike Galbraith
2018-02-09 12:35               ` Sebastian Andrzej Siewior
2018-02-15 16:13     ` Frederic Weisbecker
2018-02-15 16:58       ` Sebastian Andrzej Siewior
2018-01-19 15:46 ` [RFC PATCH 3/4] softirq: Defer to workqueue when rescheduling is needed Frederic Weisbecker
2018-01-19 15:46 ` [RFC PATCH 4/4] softirq: Replace ksoftirqd with workqueues entirely Frederic Weisbecker
2018-01-22 19:58 ` [RFC PATCH 0/4] softirq: Per vector threading v3 Mauro Carvalho Chehab
2018-01-23 10:13 ` Paolo Abeni
2018-01-23 12:32   ` Dmitry Safonov
2018-01-24  2:12     ` Frederic Weisbecker
2018-01-23 16:22   ` David Miller
2018-01-23 16:57     ` Paolo Abeni
2018-01-23 17:42       ` Linus Torvalds [this message]
2018-01-23 18:01         ` Mike Galbraith
2018-01-23 18:24         ` David Miller
2018-01-24  1:57           ` Frederic Weisbecker
2018-01-24  2:01             ` Frederic Weisbecker
2018-01-24 14:54         ` Paolo Abeni
2018-01-24 15:05           ` David Miller
2018-01-24 16:11             ` Paolo Abeni
2018-02-07 14:18 ` Mauro Carvalho Chehab
2018-03-01 15:21   ` Frederic Weisbecker

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