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



Hi

I can only comment on some of your questions as I also can't say to
understand this completely.

> Then, blkio.throttle can be used to set actual hard limits on IO
> consumption -- like, no more than 10Mbps for this VM. I can already do
> this with blkio cgroups, but just not from libvirt -- yes?

Yes.

But bear in mind that this only works for sync I/O, not for buffered I/O
(read my discussion with Gui).

> Like many people using libvirt, I only use my hosts for running VMs, and
> I am most interested in limiting IO operations per host to make sure
> that no host monopolizes our SAN. Is there a way for me to just set a
> hard IO throttle limit for libvirt as a whole which would apply to all
> child VMs created by libvirt? I saw a discussion on this list regarding
> group hierarchy, but it went over my head.

I did not read the other discussion, but this comes to my mind when
thinking about your question: You could try to put the libvirtd process
into a cgroup that has certain limits configured. Every spawned child of
this process will inherit those limits.

Not sure if a VM is actually a libvirtd-child though, since at least
"ps" shows them as init's children on my systems.

If you try this, please report back what you did and how it worked.

Regards
Dominik


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