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Subject: Re: [PATCHSET block/for-next] IO cost model based work-conserving
 porportional controller
From:   Paolo Valente <paolo.valente@linaro.org>
In-Reply-To: <20190614175642.GA657710@devbig004.ftw2.facebook.com>
Date:   Tue, 20 Aug 2019 12:48:09 +0200
Cc:     Jens Axboe <axboe@kernel.dk>, newella@fb.com, clm@fb.com,
        Josef Bacik <josef@toxicpanda.com>, dennisz@fb.com,
        Li Zefan <lizefan@huawei.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-block <linux-block@vger.kernel.org>, kernel-team@fb.com,
        cgroups@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net,
        kafai@fb.com, songliubraving@fb.com, yhs@fb.com,
        bpf@vger.kernel.org
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Message-Id: <5A63F937-F7B5-4D09-9DB4-C73D6F571D50@linaro.org>
References: <20190614015620.1587672-1-tj@kernel.org>
 <20190614175642.GA657710@devbig004.ftw2.facebook.com>
To:     Tejun Heo <tj@kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
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> Il giorno 14 giu 2019, alle ore 19:56, Tejun Heo <tj@kernel.org> ha =
scritto:
>=20
> On Thu, Jun 13, 2019 at 06:56:10PM -0700, Tejun Heo wrote:
> ...
>> The patchset is also available in the following git branch.
>>=20
>> git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git =
review-iow
>=20
> Updated patchset available in the following branch.  Just build fixes
> and cosmetic changes for now.
>=20
>  git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git =
review-iow-v2
>=20

Hi Tejun,
I'm running the kernel in your tree above, in an Ubuntu 18.04.

After unmounting the v1 blkio controller that gets mounted at startup
I have created v2 root as follows

$ mount -t cgroup2 none /cgroup

Then I have:
$ ls /cgroup
cgroup.controllers  cgroup.max.descendants  cgroup.stat             =
cgroup.threads  io.weight.cost_model  system.slice
cgroup.max.depth    cgroup.procs            cgroup.subtree_control  =
init.scope      io.weight.qos         user.slice

But the following command gives no output:
$ cat /cgroup/io.weight.qos=20

And, above all,
$ echo 1 > /cgroup/io.weight.qos=20
bash: echo: write error: Invalid argument

No complain in the kernel log.

What am I doing wrong? How can I make the controller work?

Thanks,
Paolo

> Thanks.
>=20
> --=20
> tejun