From: Jens Axboe <axboe@kernel.dk>
To: Boaz Harrosh <boaz@plexistor.com>, Phil Auld <pauld@redhat.com>,
Ming Lei <ming.lei@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Dave Chinner <david@fromorbit.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>,
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 09:19:29 -0700 [thread overview]
Message-ID: <8c02ab43-3880-68db-f293-9958510fb29e@kernel.dk> (raw)
In-Reply-To: <93de0f75-3664-c71e-9947-5b37ae935ddc@plexistor.com>
On 11/21/19 8:02 AM, Boaz Harrosh wrote:
> On 21/11/2019 16:12, Phil Auld wrote:
> <>
>>
>> The scheduler doesn't know if the queued_work submitter is going to go to sleep.
>> That's why I was singling out AIO. My understanding of it is that you submit the IO
>> and then keep going. So in that case it might be better to pick a node-local nearby
>> cpu instead. But this is a user of work queue issue not a scheduler issue.
>>
>
> We have a very similar long standing problem in our system (zufs), that we had to do
> hacks to fix.
>
> We have seen these CPU bouncing exacly as above in fio and more
> benchmarks, Our final analysis was:
>
> One thread is in wait_event() if the wake_up() is on the same CPU as
> the waiter, on some systems usually real HW and not VMs, would bounce
> to a different CPU. Now our system has an array of worker-threads
> bound to each CPU. an incoming thread chooses a corresponding cpu
> worker-thread, let it run, waiting for a reply, then when the
> worker-thread is done it will do a wake_up(). Usually its fine and the
> wait_event() stays on the same CPU. But on some systems it will wakeup
> in a different CPU.
>
> Now this is a great pity because in our case and the work_queue case
> and high % of places the thread calling wake_up() will then
> immediately go to sleep on something. (Work done lets wait for new
> work)
>
> I wish there was a flag to wake_up() or to the event object that says
> to relinquish the remaning of the time-slice to the waiter on same
> CPU, since I will be soon sleeping.
Isn't that basically what wake_up_sync() is?
--
Jens Axboe
next prev parent reply other threads:[~2019-11-21 16:19 UTC|newest]
Thread overview: 64+ 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 [this message]
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
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
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