From: "Paul E. McKenney" <paulmck@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Lai Jiangshan <jiangshanlai@gmail.com>,
linux-kernel@vger.kernel.org,
Valentin Schneider <valentin.schneider@arm.com>,
Qian Cai <cai@redhat.com>,
Vincent Donnefort <vincent.donnefort@arm.com>,
Dexuan Cui <decui@microsoft.com>,
Lai Jiangshan <laijs@linux.alibaba.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH -tip V3 0/8] workqueue: break affinity initiatively
Date: Mon, 11 Jan 2021 13:50:52 -0800 [thread overview]
Message-ID: <20210111215052.GA19589@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20210111180907.GE2743@paulmck-ThinkPad-P72>
On Mon, Jan 11, 2021 at 10:09:07AM -0800, Paul E. McKenney wrote:
> On Mon, Jan 11, 2021 at 06:16:39PM +0100, Peter Zijlstra wrote:
> >
> > While thinking more about this, I'm thinking a big part of the problem
> > is that we're not dinstinguishing between geniuine per-cpu kthreads and
> > kthreads that just happen to be per-cpu.
> >
> > Geniuine per-cpu kthreads are kthread_bind() and have PF_NO_SETAFFINITY,
> > but sadly a lot of non-per-cpu kthreads, that might happen to still be
> > per-cpu also have that -- again workqueue does that even to it's unbound
> > workers :-(
> >
> > Now, anything created by smpboot, is created through
> > kthread_create_on_cpu() and that additionally sets to_kthread(p)->flags
> > KTHREAD_IS_PER_CPU.
> >
> > And I'm thinking that might be sufficient, if we modify
> > is_per_cpu_kthread() to check that, then we only match smpboot threads
> > (which include the hotplug and stopper threads, but notably not the idle
> > thread)
> >
> > Sadly it appears like io_uring() uses kthread_create_on_cpu() without
> > then having any hotplug crud on, so that needs additinoal frobbing.
> >
> > Also, init_task is PF_KTHREAD but doesn't have a struct kthread on.. and
> > I suppose bound workqueues don't go through this either.
> >
> > Let me rummage around a bit...
> >
> > This seems to not insta-explode... opinions?
>
> It passes quick tests on -rcu both with and without the rcutorture fixes,
> which is encouraging. I will start a more vigorous test in about an hour.
And 672 ten-minute instances of RUDE01 passed with this patch applied
and with my rcutorture patch reverted. So looking good, thank you!!!
Thanx, Paul
next prev parent reply other threads:[~2021-01-11 21:52 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-26 2:51 [PATCH -tip V3 0/8] workqueue: break affinity initiatively Lai Jiangshan
2020-12-26 2:51 ` [PATCH -tip V3 1/8] workqueue: use cpu_possible_mask instead of cpu_active_mask to break affinity Lai Jiangshan
2020-12-26 2:51 ` [PATCH -tip V3 2/8] workqueue: Manually break affinity on pool detachment Lai Jiangshan
2020-12-26 2:51 ` [PATCH -tip V3 3/8] workqueue: introduce wq_online_cpumask Lai Jiangshan
2021-01-04 13:56 ` Peter Zijlstra
2021-01-05 2:41 ` Lai Jiangshan
2021-01-05 2:53 ` Lai Jiangshan
2021-01-05 8:23 ` Lai Jiangshan
2021-01-05 13:17 ` Peter Zijlstra
2021-01-05 14:37 ` Lai Jiangshan
2021-01-05 14:40 ` Lai Jiangshan
2021-01-05 16:24 ` Peter Zijlstra
2020-12-26 2:51 ` [PATCH -tip V3 4/8] workqueue: use wq_online_cpumask in restore_unbound_workers_cpumask() Lai Jiangshan
2020-12-26 2:51 ` [PATCH -tip V3 5/8] workqueue: Manually break affinity on hotplug for unbound pool Lai Jiangshan
[not found] ` <20201226101631.5448-1-hdanton@sina.com>
2020-12-27 14:04 ` Lai Jiangshan
2020-12-26 2:51 ` [PATCH -tip V3 6/8] workqueue: reorganize workqueue_online_cpu() Lai Jiangshan
2020-12-26 2:51 ` [PATCH -tip V3 7/8] workqueue: reorganize workqueue_offline_cpu() unbind_workers() Lai Jiangshan
2020-12-26 2:51 ` [PATCH -tip V3 8/8] workqueue: Fix affinity of kworkers when attaching into pool Lai Jiangshan
[not found] ` <20201229100639.2086-1-hdanton@sina.com>
2020-12-29 10:13 ` Lai Jiangshan
2021-01-08 11:46 ` [PATCH -tip V3 0/8] workqueue: break affinity initiatively Peter Zijlstra
2021-01-11 10:07 ` Thomas Gleixner
2021-01-11 11:01 ` Peter Zijlstra
2021-01-11 15:00 ` Paul E. McKenney
2021-01-11 17:16 ` Peter Zijlstra
2021-01-11 18:09 ` Paul E. McKenney
2021-01-11 21:50 ` Paul E. McKenney [this message]
2021-01-12 17:14 ` Paul E. McKenney
2021-01-12 23:53 ` Paul E. McKenney
2021-01-15 9:11 ` Peter Zijlstra
2021-01-15 13:04 ` Peter Zijlstra
2021-01-16 6:00 ` Lai Jiangshan
2021-01-11 19:21 ` Valentin Schneider
2021-01-11 20:23 ` Peter Zijlstra
2021-01-11 22:47 ` Valentin Schneider
2021-01-12 4:33 ` Lai Jiangshan
2021-01-12 14:53 ` Peter Zijlstra
2021-01-12 15:38 ` Lai Jiangshan
2021-01-13 11:10 ` Peter Zijlstra
2021-01-13 12:00 ` Lai Jiangshan
2021-01-13 12:57 ` Lai Jiangshan
2021-01-12 17:52 ` Valentin Schneider
2021-01-12 14:57 ` Jens Axboe
2021-01-12 15:51 ` Peter Zijlstra
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