Re: [PATCH 1/4] cfq-iosced: Remove the check for same cfq group fromallow_merge

From: Gui Jianfeng
Date: Thu Dec 17 2009 - 04:30:40 EST

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@xxxxxxxxxx>

Reviewed-by: Gui Jianfeng <guijianfeng@xxxxxxxxxxxxxx>

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