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SubjectRe: [PATCHSET block/for-next] IO cost model based work-conserving porportional controller
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> Il giorno 20 ago 2019, alle ore 12:48, Paolo Valente <paolo.valente@linaro.org> ha scritto:
>
>
>
>> Il giorno 14 giu 2019, alle ore 19:56, Tejun Heo <tj@kernel.org> ha scritto:
>>
>> On Thu, Jun 13, 2019 at 06:56:10PM -0700, Tejun Heo wrote:
>> ...
>>> The patchset is also available in the following git branch.
>>>
>>> git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git review-iow
>>
>> Updated patchset available in the following branch. Just build fixes
>> and cosmetic changes for now.
>>
>> git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git review-iow-v2
>>
>
> 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
>
> And, above all,
> $ echo 1 > /cgroup/io.weight.qos
> bash: echo: write error: Invalid argument
>
> No complain in the kernel log.
>
> What am I doing wrong? How can I make the controller work?
>

I made it, sorry for my usual silly questions (for some reason, I
thought the controller could be enabled globally by just passing a 1).

The problem now is that the controller doesn't seem to work. I've
emulated 16 clients doing I/O on a SATA SSD. One client, the target,
does random reads, while the remaining 15 clients, the interferers, do
sequential reads.

Each client is encapsulated in a separate group, but whatever weight
is assigned to the target group, the latter gets the same, extremely
low bandwidth. I have tried with even the maximum weight ratio, i.e.,
1000 for the target and only 1 for each interferer. Here are the
results, compared with BFQ (bandwidth in MB/s):

io.weight BFQ
0.2 3.7

I ran this test with the script S/bandwidth-latency/bandwidth-latency.sh
of the S benchmark suite [1], invoked as follows:
sudo ./bandwidth-latency.sh -t randread -s none -b weight -n 15 -w 1000 -W 1

The above command simply creates groups, assigns weights as follows

echo 1 > /cgroup/InterfererGroup0/io.weight
echo 1 > /cgroup/InterfererGroup1/io.weight
...
echo 1 > /cgroup/InterfererGroup14/io.weight
echo 1000 > /cgroup/interfered/io.weight

and makes one fio instance generate I/O for each group. The bandwidth
reported above is that reported by the fio instance emulating the
target client.

Am I missing something?

Thanks,
Paolo

[1] https://github.com/Algodev-github/S


> Thanks,
> Paolo
>
>> Thanks.
>>
>> --
>> tejun
>

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