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

Hi back with some testing results. So here's what I did and found out: The host system has 2 12 core CPUs and 128 GB of Ram. I have 8 test VMs named kernel1 to kernel8. Each VM has 4 VCPUs, 2 GB of RAm and one disk, which is an lv on the host. Cache mode is "none": for vm in kernel1 kernel2 kernel3 kernel4 kernel5 kernel6 kernel7 kernel8; do virsh dumpxml $vm|grep cache; done <driver name='qemu' type='raw' cache='none'/> <driver name='qemu' type='raw' cache='none'/> <driver name='qemu' type='raw' cache='none'/> <driver name='qemu' type='raw' cache='none'/> <driver name='qemu' type='raw' cache='none'/> <driver name='qemu' type='raw' cache='none'/> <driver name='qemu' type='raw' cache='none'/> <driver name='qemu' type='raw' cache='none'/> My goal is to give more I/O time to kernel1 and kernel2 than to the rest of the VMs. mount -t cgroup -o blkio none /mnt cd /mnt mkdir important mkdir notimportant echo 1000 > important/blkio.weight echo 100 > notimportant/blkio.weight for vm in kernel3 kernel4 kernel5 kernel6 kernel7 kernel8; do cd /proc/$(pgrep -f "qemu-kvm.*$vm")/task for task in *; do /bin/echo $task > /mnt/notimportant/tasks done done for vm in kernel1 kernel2; do cd /proc/$(pgrep -f "qemu-kvm.*$vm")/task for task in *; do /bin/echo $task > /mnt/important/tasks done done Then I used cssh to connect to all 8 VMs and execute dd if=/dev/zero of=testfile bs=1M count=1500 in all VMs simultaneously. Results are: kernel1: 47.5593 s, 33.1 MB/s kernel2: 60.1464 s, 26.2 MB/s kernel3: 74.204 s, 21.2 MB/s kernel4: 77.0759 s, 20.4 MB/s kernel5: 65.6309 s, 24.0 MB/s kernel6: 81.1402 s, 19.4 MB/s kernel7: 70.3881 s, 22.3 MB/s kernel8: 77.4475 s, 20.3 MB/s Results vary a little bit from run to run, but it is nothing spectacular, as weights of 1000 vs. 100 would suggest. So I went and tried to throttle I/O of kernel3-8 to 10MB/s instead of weighing I/O. First I rebooted everything so that no old configuration of cgroup was left in place and then setup everything except the 100 and 1000 weight configuration. quote from blkio.txt: ------------ - blkio.throttle.write_bps_device - Specifies upper limit on WRITE rate to the device. IO rate is specified in bytes per second. Rules are per deivce. Following is the format. echo "<major>:<minor> <rate_bytes_per_second>" > /cgrp/blkio.write_bps_device ------------- for vm in kernel1 kernel2 kernel3 kernel4 kernel5 kernel6 kernel7 kernel8; do ls -lH /dev/vdisks/$vm; done brw-rw---- 1 root root 254, 23 Feb 18 13:45 /dev/vdisks/kernel1 brw-rw---- 1 root root 254, 24 Feb 18 13:45 /dev/vdisks/kernel2 brw-rw---- 1 root root 254, 25 Feb 18 13:45 /dev/vdisks/kernel3 brw-rw---- 1 root root 254, 26 Feb 18 13:45 /dev/vdisks/kernel4 brw-rw---- 1 root root 254, 27 Feb 18 13:45 /dev/vdisks/kernel5 brw-rw---- 1 root root 254, 28 Feb 18 13:45 /dev/vdisks/kernel6 brw-rw---- 1 root root 254, 29 Feb 18 13:45 /dev/vdisks/kernel7 brw-rw---- 1 root root 254, 30 Feb 18 13:45 /dev/vdisks/kernel8 /bin/echo 254:25 10000000 > /mnt/notimportant/blkio.throttle.write_bps_device /bin/echo 254:26 10000000 > /mnt/notimportant/blkio.throttle.write_bps_device /bin/echo 254:27 10000000 > /mnt/notimportant/blkio.throttle.write_bps_device /bin/echo 254:28 10000000 > /mnt/notimportant/blkio.throttle.write_bps_device /bin/echo 254:29 10000000 > /mnt/notimportant/blkio.throttle.write_bps_device /bin/echo 254:30 10000000 > /mnt/notimportant/blkio.throttle.write_bps_device /bin/echo 254:30 10000000 > /mnt/notimportant/blkio.throttle.write_bps_device Then I ran the previous test again. This resulted in an ever increasing load (last I checked was ~ 300) on the host system. (This is perfectly reproducible). uptime Fri Feb 18 14:42:17 2011 14:42:17 up 12 min, 9 users, load average: 286.51, 142.22, 56.71 So, at least in my case, it does not seem to work too well (yet). Regards Dominik