From: Jens Axboe <jaxboe@fusionio.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
Thomas Gleixner <tglx@linutronix.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>, Tejun Heo <tj@kernel.org>
Subject: Re: [RFC][PATCH 1/3] sched, block: Move unplug
Date: Wed, 22 Jun 2011 18:04:39 +0200 [thread overview]
Message-ID: <4E021297.4000505@fusionio.com> (raw)
In-Reply-To: <20110622150825.GE17010@redhat.com>
On 2011-06-22 17:08, Vivek Goyal wrote:
> On Wed, Jun 22, 2011 at 04:38:01PM +0200, Peter Zijlstra wrote:
>> On Wed, 2011-06-22 at 16:30 +0200, Thomas Gleixner wrote:
>>>> It is supposedly a real problem, not just an inkling. It's not about
>>>> recursing indefinitely, the plug is fairly bounded. But the IO dispatch
>>>> path can be pretty deep, and if you hit that deep inside the reclaim or
>>>> file system write path, then you get dangerously close. Dave Chinner
>>>> posted some numbers in the 2.6.39-rc1 time frame showing how close we
>>>> got.
>>>
>>> Fair enough.
>>
>>> Ok. So we move it out and keep the from_scheduler flag so that code
>>> does not go down the IO path from there.
>>
>> Won't punting the plug to a worker thread wreck all kinds of io
>> accounting due to the wrong task doing the actual io submission?
>
> I think all the accounting will the done in IO submission path and
> while IO is added to plug. This is just plug flush so should not
> have effect on accounting.
Exactly, this is just the insert operation, so no worries there. The
request are fully "formulated".
--
Jens Axboe
next prev parent reply other threads:[~2011-06-22 16:04 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-21 23:34 [RFC][PATCH 0/3] Move WQ,unplug scheduler hooks Peter Zijlstra
2011-06-21 23:34 ` [RFC][PATCH 1/3] sched, block: Move unplug Peter Zijlstra
2011-06-22 7:01 ` Jens Axboe
2011-06-22 13:53 ` Thomas Gleixner
2011-06-22 14:01 ` Jens Axboe
2011-06-22 14:30 ` Thomas Gleixner
2011-06-22 14:38 ` Peter Zijlstra
2011-06-22 15:08 ` Vivek Goyal
2011-06-22 16:04 ` Jens Axboe [this message]
2011-06-21 23:34 ` [RFC][PATCH 2/3] sched, workqueue: Move WQ-sleeper wakeup Peter Zijlstra
2011-06-22 9:24 ` Tejun Heo
2011-06-22 9:27 ` Peter Zijlstra
2011-06-22 9:37 ` Tejun Heo
2011-06-22 13:47 ` Thomas Gleixner
2011-06-21 23:34 ` [RFC][PATCH 3/3] block: Break long IRQ disabled region Peter Zijlstra
2011-06-22 7:03 ` Jens Axboe
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