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Message-ID: <4B29F92B.2040602@cn.fujitsu.com>
Date: Thu, 17 Dec 2009 17:26:03 +0800
From: Gui Jianfeng <guijianfeng@...fujitsu.com>
To: Vivek Goyal <vgoyal@...hat.com>
CC: linux-kernel@...r.kernel.org, jens.axboe@...cle.com,
nauman@...gle.com, lizf@...fujitsu.com, ryov@...inux.co.jp,
fernando@....ntt.co.jp, taka@...inux.co.jp, jmoyer@...hat.com,
m-ikeda@...jp.nec.com, czoccolo@...il.com, Alan.Brunelle@...com
Subject: Re: [PATCH 1/4] cfq-iosced: Remove the check for same cfq group from
allow_merge
Vivek Goyal wrote:
> o allow_merge() already checks if submitting task is pointing to same cfqq
> as rq has been queued in. If everything is fine, we should not be having
> a task in one cgroup and having a pointer to cfqq in other cgroup.
>
> Well I guess in some situations it can happen and that is, when a random
> IO queue has been moved into root cgroup for group_isolation=0. In
> this case, tasks's cgroup/group is different from where actually cfqq is,
> but this is intentional and in this case merging should be allowed.
>
> The second situation is where due to close cooperator patches, multiple
> processes can be sharing a cfqq. If everything implemented right, we should
> not end up in a situation where tasks from different processes in different
> groups are sharing the same cfqq as we allow merging of cooperating queues
> only if they are in same group.
>
> Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
Reviewed-by: Gui Jianfeng <guijianfeng@...fujitsu.com>
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