linux-kernel - Re: [PATCHSET block/for-4.2/writeback] block, cgroup: make cfq charge async IOs to the appropriate blkcgs

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Message-ID: <x491thmhtej.fsf@segfault.boston.devel.redhat.com>
Date:	Mon, 08 Jun 2015 15:49:56 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	axboe@...nel.dk, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org, vgoyal@...hat.com,
	avanzini.arianna@...il.com
Subject: Re: [PATCHSET block/for-4.2/writeback] block, cgroup: make cfq charge async IOs to the appropriate blkcgs

Tejun Heo <tj@...nel.org> writes:

> Hello,
>
> cfq has always charged all async IOs to the root cgroup.  It didn't
> have much choice as writeback didn't know about cgroups and there was
> no way to tell who to blame for a given writeback IO.  writeback
> finally grew support for cgroups and now tags each writeback IO with
> the appropriate cgroup to charge it against.
>
> This patchset updates cfq so that it follows the blkcg each bio is
> tagged with.  Async cfq_queues are now shared across cfq_group, which
> is per-cgroup, instead of per-request_queue cfq_data.  This makes all
> IOs follow the weight based IO resource distribution implemented by
> cfq.
>
> This patchset contains the following 8 patches.
>
>  0001-cfq-iosched-simplify-control-flow-in-cfq_get_queue.patch
>  0002-cfq-iosched-fix-async-oom-queue-handling.patch
>  0003-cfq-iosched-fix-oom-cfq_queue-ref-leak-in-cfq_set_re.patch
>  0004-cfq-iosched-minor-cleanups.patch
>  0005-cfq-iosched-remove-gfp_mask-from-cfq_find_alloc_queu.patch
>  0006-cfq-iosched-move-cfq_group-determination-from-cfq_fi.patch
>  0007-cfq-iosched-fold-cfq_find_alloc_queue-into-cfq_get_q.patch
>  0008-cfq-iosched-charge-async-IOs-to-the-appropriate-blkc.patch

Hi, Tejun,

Assuming you're ok with dropping patch 5, I'll review patches 6-8 once
they've been reworked to account for that.  I took a look at them, and
they look OK to me.  But, if they are going to change, I'd rather wait
to ack the final versions.

Cheers,
Jeff
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