From: Phil Auld <pauld@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>,
Ming Lei <ming.lei@redhat.com>,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org,
Jeff Moyer <jmoyer@redhat.com>,
Dave Chinner <dchinner@redhat.com>,
Eric Sandeen <sandeen@redhat.com>, Christoph Hellwig <hch@lst.de>,
Jens Axboe <axboe@kernel.dk>, Ingo Molnar <mingo@redhat.com>,
Tejun Heo <tj@kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>
Subject: Re: single aio thread is migrated crazily by scheduler
Date: Thu, 21 Nov 2019 09:21:36 -0500 [thread overview]
Message-ID: <20191121142136.GB18443@pauld.bos.csb> (raw)
In-Reply-To: <20191121132937.GW4114@hirez.programming.kicks-ass.net>
On Thu, Nov 21, 2019 at 02:29:37PM +0100 Peter Zijlstra wrote:
> On Wed, Nov 20, 2019 at 05:03:13PM -0500, Phil Auld wrote:
> > On Wed, Nov 20, 2019 at 08:16:36PM +0100 Peter Zijlstra wrote:
> > > On Tue, Nov 19, 2019 at 07:40:54AM +1100, Dave Chinner wrote:
>
> > > > Yes, that's precisely the problem - work is queued, by default, on a
> > > > specific CPU and it will wait for a kworker that is pinned to that
> > >
> > > I'm thinking the problem is that it doesn't wait. If it went and waited
> > > for it, active balance wouldn't be needed, that only works on active
> > > tasks.
> >
> > Since this is AIO I wonder if it should queue_work on a nearby cpu by
> > default instead of unbound.
>
> The thing seems to be that 'unbound' is in fact 'bound'. Maybe we should
> fix that. If the load-balancer were allowed to move the kworker around
> when it didn't get time to run, that would probably be a better
> solution.
>
Yeah, I'm not convinced this is actually a scheduler issue.
> Picking another 'bound' cpu by random might create the same sort of
> problems in more complicated scenarios.
>
> TJ, ISTR there used to be actually unbound kworkers, what happened to
> those? or am I misremembering things.
>
> > > Lastly,
> > > one other thing to try is -next. Vincent reworked the load-balancer
> > > quite a bit.
> > >
> >
> > I've tried it with the lb patch series. I get basically the same results.
> > With the high granularity settings I get 3700 migrations for the 30
> > second run at 4k. Of those about 3200 are active balance on stock 5.4-rc7.
> > With the lb patches it's 3500 and 3000, a slight drop.
>
> Thanks for testing that. I didn't expect miracles, but it is good to
> verify.
>
> > Using the default granularity settings 50 and 22 for stock and 250 and 25.
> > So a few more total migrations with the lb patches but about the same active.
>
> Right, so the granularity thing interacts with the load-balance period.
> By pushing it up, as some people appear to do, makes it so that what
> might be a temporal imablance is perceived as a persitent imbalance.
>
> Tying the load-balance period to the gramularity is something we could
> consider, but then I'm sure, we'll get other people complaining the
> doesn't balance quick enough anymore.
>
Thanks. These are old tuned settings that have been carried along. They may
not be right for newer kernels anyway.
--
next prev parent reply other threads:[~2019-11-21 14:21 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-14 11:31 single aio thread is migrated crazily by scheduler Ming Lei
2019-11-14 13:14 ` Peter Zijlstra
2019-11-15 0:09 ` Ming Lei
2019-11-15 14:16 ` Ming Lei
2019-11-14 23:54 ` Dave Chinner
2019-11-15 1:08 ` Ming Lei
2019-11-15 4:56 ` Dave Chinner
2019-11-15 7:08 ` Ming Lei
2019-11-15 23:40 ` Dave Chinner
2019-11-16 6:31 ` Ming Lei
2019-11-18 9:21 ` Peter Zijlstra
2019-11-18 14:54 ` Vincent Guittot
2019-11-18 20:40 ` Dave Chinner
2019-11-20 19:16 ` Peter Zijlstra
2019-11-20 22:03 ` Phil Auld
2019-11-21 4:12 ` Ming Lei
2019-11-21 14:12 ` Phil Auld
2019-11-21 15:02 ` Boaz Harrosh
2019-11-21 16:19 ` Jens Axboe
2019-12-09 16:58 ` Srikar Dronamraju
2019-11-21 22:10 ` Dave Chinner
2019-11-21 13:29 ` Peter Zijlstra
2019-11-21 14:21 ` Phil Auld [this message]
2019-12-09 16:51 ` Srikar Dronamraju
2019-12-09 23:17 ` Dave Chinner
2019-12-10 3:27 ` Srikar Dronamraju
2019-12-10 5:43 ` [PATCH v2] sched/core: Preempt current task in favour of bound kthread Srikar Dronamraju
2019-12-10 9:26 ` Peter Zijlstra
2019-12-10 9:33 ` Peter Zijlstra
2019-12-10 10:18 ` Srikar Dronamraju
2019-12-10 10:16 ` Srikar Dronamraju
2019-12-10 9:43 ` Vincent Guittot
2019-12-10 10:11 ` Srikar Dronamraju
2019-12-10 11:02 ` Vincent Guittot
2019-12-10 17:23 ` [PATCH v3] " Srikar Dronamraju
2019-12-11 17:38 ` [PATCH v4] " Srikar Dronamraju
2019-12-11 22:46 ` Dave Chinner
2019-12-12 10:10 ` Peter Zijlstra
2019-12-12 10:14 ` Peter Zijlstra
2019-12-12 10:23 ` Peter Zijlstra
2019-12-12 11:20 ` Vincent Guittot
2019-12-12 13:12 ` Peter Zijlstra
2019-12-12 15:07 ` Srikar Dronamraju
2019-12-12 15:15 ` Peter Zijlstra
2019-12-13 5:32 ` Srikar Dronamraju
2019-11-18 16:26 ` single aio thread is migrated crazily by scheduler Srikar Dronamraju
2019-11-18 21:18 ` Dave Chinner
2019-11-19 8:54 ` Ming Lei
[not found] ` <20191128094003.752-1-hdanton@sina.com>
2019-11-28 9:53 ` Vincent Guittot
2019-12-02 2:46 ` Ming Lei
2019-12-02 4:02 ` Dave Chinner
2019-12-02 4:22 ` Ming Lei
2019-12-02 13:45 ` Vincent Guittot
2019-12-02 21:22 ` Phil Auld
2019-12-03 9:45 ` Vincent Guittot
2019-12-04 13:50 ` Ming Lei
2019-12-02 23:53 ` Dave Chinner
2019-12-03 0:18 ` Ming Lei
2019-12-03 13:34 ` Vincent Guittot
2019-12-02 7:39 ` Juri Lelli
2019-12-02 3:08 ` Dave Chinner
[not found] ` <20191202090158.15016-1-hdanton@sina.com>
2019-12-02 23:06 ` Dave Chinner
[not found] ` <20191203131514.5176-1-hdanton@sina.com>
2019-12-03 22:29 ` Dave Chinner
[not found] ` <20191204102903.896-1-hdanton@sina.com>
2019-12-04 22:59 ` Dave Chinner
2019-11-27 0:43 ` 0da4873c66: xfstests.generic.287.fail kernel test robot
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