Subject: Re: Do not overload dispatch queue (Was: Re: IO scheduler based IO
 controller V10)
From: Mike Galbraith <efault@gmx.de>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <jens.axboe@oracle.com>, Ingo Molnar <mingo@elte.hu>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Ulrich Lukas <stellplatz-nr.13a@datenparkplatz.de>,
       linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org,
       dm-devel@redhat.com, nauman@google.com, dpshah@google.com,
       lizf@cn.fujitsu.com, mikew@google.com, fchecconi@gmail.com,
       paolo.valente@unimore.it, ryov@valinux.co.jp, fernando@oss.ntt.co.jp,
       jmoyer@redhat.com, dhaval@linux.vnet.ibm.com, balbir@linux.vnet.ibm.com,
       righi.andrea@gmail.com, m-ikeda@ds.jp.nec.com, agk@redhat.com,
       akpm@linux-foundation.org, peterz@infradead.org, jmarchan@redhat.com,
       riel@redhat.com
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Date: Sat, 03 Oct 2009 16:02:33 +0200
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On Sat, 2009-10-03 at 09:56 -0400, Vivek Goyal wrote:

> I have kept the overload delay period as "cfq_slice_sync" same as Mike had
> done. We shall have to experiment what is a good waiting perioed. Is 100ms
> too long if we are waiting for a request from same process which recently
> finished IO and we did not enable idle on it.
> 
> I guess we can tweak the delay period as we move along.

I kept the delay period very short to minimize possible damage. Without
the idle thing, it wasn't enough, but with, worked a treat, as does your
patch.

	-Mike

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