linux-kernel - Re: [PATCH] IO-Controller: clear ioq wait flag if a request goes into that ioq

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Date:	Fri, 21 Aug 2009 08:57:27 +0800
From:	Gui Jianfeng <guijianfeng@...fujitsu.com>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, dm-devel@...hat.com,
	jens.axboe@...cle.com, ryov@...inux.co.jp,
	balbir@...ux.vnet.ibm.com, righi.andrea@...il.com,
	nauman@...gle.com, dpshah@...gle.com, lizf@...fujitsu.com,
	mikew@...gle.com, fchecconi@...il.com, paolo.valente@...more.it,
	fernando@....ntt.co.jp, s-uchida@...jp.nec.com, taka@...inux.co.jp,
	jmoyer@...hat.com, dhaval@...ux.vnet.ibm.com,
	m-ikeda@...jp.nec.com, agk@...hat.com, akpm@...ux-foundation.org,
	peterz@...radead.org, jmarchan@...hat.com
Subject: Re: [PATCH] IO-Controller: clear ioq wait flag if a request goes
 into that ioq

Vivek Goyal wrote:
> On Thu, Aug 20, 2009 at 09:46:10AM +0800, Gui Jianfeng wrote:
>> Vivek Goyal wrote:
>> ...
>>>  		/*
>>>  		 * Remember that we saw a request from this process, but
>>> @@ -1940,7 +2013,7 @@ void elv_ioq_request_add(struct request_queue *q, struct request *rq)
>>>  		 * has other work pending, don't risk delaying until the
>>>  		 * idle timer unplug to continue working.
>>>  		 */
>>> -		if (elv_ioq_wait_request(ioq)) {
>>> +		if (group_wait || elv_ioq_wait_request(ioq)) {
>> Hi Vivek,
>>
>> I guess we need to clear ioq_wait_request flags if there are requests to 
>> go in this ioq. Otherwise, once waitting request on ioq, it will go into
>> this path every time when a request is enqueued.
>>
>> Signed-off-by: Gui Jianfeng <guijianfeng@...fujitsu.com>
> 
> Hi Gui,
> 
> It does sound like that we need to clear ioq wait_request flag here. In
> fact upstream CFQ code is also not clearing this flag. Looking at the
> code, can't think why it should not be cleared here.
> 
> Can you please also generate a patch for CFQ and post to lkml.
> 

Sure, will do.

-- 
Regards
Gui Jianfeng

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