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SubjectRe: [PATCH 1/9] io-throttle documentation
KAMEZAWA Hiroyuki wrote:
> On Fri, 17 Apr 2009 15:34:53 +0800
> Gui Jianfeng <guijianfeng@cn.fujitsu.com> wrote:
>
>> KAMEZAWA Hiroyuki wrote:
>>> On Tue, 14 Apr 2009 22:21:12 +0200
>>> Andrea Righi <righi.andrea@gmail.com> wrote:
>>>
>>>> +Example:
>>>> +* Create an association between an io-throttle group and a bio-cgroup group
>>>> + with "bio" and "blockio" subsystems mounted in different mount points:
>>>> + # mount -t cgroup -o bio bio-cgroup /mnt/bio-cgroup/
>>>> + # cd /mnt/bio-cgroup/
>>>> + # mkdir bio-grp
>>>> + # cat bio-grp/bio.id
>>>> + 1
>>>> + # mount -t cgroup -o blockio blockio /mnt/io-throttle
>>>> + # cd /mnt/io-throttle
>>>> + # mkdir foo
>>>> + # echo 1 > foo/blockio.bio_id
>>> Why do we need multiple cgroups at once to track I/O ?
>>> Seems complicated to me.
>> Hi Kamezawa-san,
>>
>> The original thought to implement this function is for sharing a bio-cgroup
>> with other subsystems, such as dm-ioband. If the bio-cgroup is already mounted,
>> and used by dm-ioband or others, we just need to create a association between
>> io-throttle and bio-cgroup by echo a bio-cgroup id, just like what dm-ioband does.
>>
>
> - Why we need multiple I/O controller ?
> - Why bio-cgroup cannot be a _pure_ infrastructe as page_cgroup ?
> - Why we need extra mount ?
>
> I have no answer but, IMHO,
> - only one I/O controller should be enabled at once.
> - bio cgroup should be tightly coupled with I/O controller and should work as
> infrastructure i.e. naming/tagging I/O should be automatically done by
> I/O controller. not by the user's hand.

It seems dm-ioband has to make use of bio-cgroup by the user's hand. Because dm-ioband
is not cgroup based. :(

Is that possible that another subsystem(not cgroup based, and not an IO Controller) also
would like to use bio-cgroup in the future? There's no such case at least now, so i don't
object to get rid of this part. :)

>
> Thanks,
> -Kame
>
>
>
>
>

--
Regards
Gui Jianfeng



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