Re: [libvirt] cgroup limits only affect kvm guest under certain conditions

Hi I am playing with cgroups and try to limit block io for guests. The proof of concept is: # mkdir /dev/cgroup/blkio # mount -t cgroup -o blkio blkio /dev/cgroup/blkio/ # cd blkio/ # mkdir test # cd test/ # ls -l /dev/vdisks/kirk lrwxrwxrwx 1 root root 7 2011-01-06 13:46 /dev/vdisks/kirk -> ../dm-5 # ls -l /dev/dm-5 brw-rw---- 1 root disk 253, 5 2011-01-06 13:36 /dev/dm-5 # echo "253:5 1048576" > blkio.throttle.write_bps_device # echo $$ > tasks # dd if=/dev/zero of=/dev/dm-5 bs=1M count=20 20+0 records in 20+0 records out 20971520 bytes (21 MB) copied, 20.0223 s, 1.0 MB/s So limit applies to the dd child of my shell. Now I assign /dev/dm-5 (/dev/vdisks/kirk) to a vm and echo the qemu-kvm pid into tasks. Limits are not applied, the guest can happily use max io bandwidth.