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Re: [libvirt] [PATCH 0/6 v3] Add blkio cgroup support

Dominik Klein wrote:
>> Hmm.. "blkio.weight" is used to control the Minimal Maximal Bandwidth. If you'd like
>> to control Max bandwidth to let your guests become I/O hungery. "blkio.throttle.*"
>> should helps. But these tunables aren't supported by blkiotune for the time being.
>> I'm considering to implement them in the future.
> Hm, maybe I was not clear then. Let me try to rephrase.
> As far as I understand, and as far as I saw during my tests, the blkio
> controller only works for sync I/O requests (eg dd with oflag=direct).
> Buffered I/O is not part of the control.

Yes, you are right.

> And since a VM's I/O is most likely buffered in some fashion, this does
> not have any effect. That's what my tests showed.

how about the start Guest with option "cache=none" to bypass pagecache?
This should help i think.

> Did your tests show something different? Maybe I did things wrong then.

I think blkio cgroup should work if "cache=none" is set. But I didn't try it,
Will try it later.


> Regards
> Dominik

Gui Jianfeng

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