From: Jens Axboe <jens.axboe@oracle.com>
To: Divyesh Shah <dpshah@google.com>
Cc: vgoyal@redhat.com, linux-kernel@vger.kernel.org,
nauman@google.com, ctalbott@google.com
Subject: Re: [PATCH] cfq-iosched: Fix the incorrect timeslice accounting with forced_dispatch.
Date: Fri, 9 Apr 2010 09:29:16 +0200 [thread overview]
Message-ID: <20100409072915.GF10103@kernel.dk> (raw)
In-Reply-To: <20100409021054.13511.52377.stgit@austin.mtv.corp.google.com>
On Thu, Apr 08 2010, Divyesh Shah wrote:
> When CFQ dispatches requests forcefully due to a barrier or changing iosched,
> it runs through all cfqq's dispatching requests and then expires each queue.
> However, it does not activate a cfqq before flushing its IOs resulting in
> using stale values for computing slice_used.
> This patch fixes it by calling activate queue before flushing reuqests from
> each queue.
>
> This is useful mostly for barrier requests because when the iosched is changing
> it really doesnt matter if we have incorrect accounting since we're going to
> break down all structures anyway.
>
> We also now expire the current timeslice before moving on with the dispatch
> to accurately account slice used for that cfqq.
Good catch, applied for 2.6.34.
--
Jens Axboe
next prev parent reply other threads:[~2010-04-09 7:29 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-09 2:19 [PATCH] cfq-iosched: Fix the incorrect timeslice accounting with forced_dispatch Divyesh Shah
2010-04-09 7:29 ` Jens Axboe [this message]
2010-04-09 14:09 ` Vivek Goyal
2010-04-09 15:25 ` Divyesh Shah
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