linux-kernel - Re: [PATCH]cfq-iosched: don't stop async queue with async requests pending

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Message-ID: <20100119223356.GC4992@redhat.com>
Date:	Tue, 19 Jan 2010 17:33:56 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	"Li, Shaohua" <shaohua.li@...el.com>
Cc:	Gui Jianfeng <guijianfeng@...fujitsu.com>,
	Corrado Zoccolo <czoccolo@...il.com>,
	"jens.axboe@...cle.com" <jens.axboe@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jmoyer@...hat.com" <jmoyer@...hat.com>,
	"yanmin_zhang@...ux.intel.com" <yanmin_zhang@...ux.intel.com>
Subject: Re: [PATCH]cfq-iosched: don't stop async queue with async requests
	pending

On Tue, Jan 19, 2010 at 08:52:01AM +0800, Li, Shaohua wrote:

[..]
> >Yes cfq_should_idle() can check for async queue and return false.
> >
> >Regarding group loosing fair share, currently all async queues are in root
> >group and not in individual groups, so this particular change should not
> >affect a lot. We will continue to idle on sync-idle and sync-noidle
> >service tree. Only async service tree is the exception.
> >
> >Once we introduce per group async queue in future, we shall have to come
> >up with something else, if need be.
> >
> >So keep this as a separate patch. I think in the presence of mixed
> >workload, (readers and buffered writers), it might give little performance
> >boost. We need to test it though.
> Ok, if you thought this method doesn't break group, here is the updated
> patch. I'm sorry to send the attached patch, my mailbox has trouble.

Hi Shaohua,

I did some testing on cfq group functionality and I did not see any
significant impact of this patch.

I am yet to write some test cases for mixed workload testing and see the
impact of this patch. Will get back to you soon.

Thanks
Vivek
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