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

Igor Serebryany wrote: > On Fri, Feb 18, 2011 at 04:12:28PM +0800, Gui Jianfeng wrote: >> "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. > I'm still a bit confused. The "weight" controls the 'percentage' of > resources the VM gets compared to other VMs (or other processes > participating in the cgroup)? If I have 5 processes running on the > system, and 4 of them are VMs using cgroups, then the VMs get 4/5s of > all CPU time for IO tasks, and each VM gets an amount of that 4/5th > proportional to it's weight? Yes? Yes, if all weight are the same.

> 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 > 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. There's no way to set this limit by libvirt. But, I think you can set the limit by hand in cgroup directory. ;) Thanks, Gui > --Igor