linux-kernel - Re: [PATCH]cfq-iosched: don't take requests with long distence as close

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Message-ID: <x494omnp2xd.fsf@segfault.boston.devel.redhat.com>
Date:	Fri, 15 Jan 2010 14:45:50 -0500
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Corrado Zoccolo <czoccolo@...il.com>
Cc:	"Zhang\, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Shaohua Li <shaohua.li@...el.com>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	"jens.axboe\@oracle.com" <jens.axboe@...cle.com>,
	"Zhang\, Yanmin" <yanmin.zhang@...el.com>
Subject: Re: [PATCH]cfq-iosched: don't take requests with long distence as  close

Corrado Zoccolo <czoccolo@...il.com> writes:

> Hi Jeff,
> I think this patch has the same flaw as Shaohua's.
> The seekiness check that you introduce in cfq_rq_close is already
> present in its caller, cfq_close_cooperator, so it is not effective.

I don't think so.  There are two queues, here.  One queue is checked by
the caller, and that is the cur_cfqq.  The __cfqq needs to also be
checked.

> Up to now, the only patch that improves this situation is the one that
> changes the unmerge policy to unmerge after a single time slice.

Yes, I definitely agree with that, and I think that patch should go in.

Cheers,
Jeff
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