Comment 0 for bug 1100843

Mark Petersen (mpetersen-peak6) wrote :

I have 2 physical hosts running Ubuntu Precise. With 1.0+noroms-0ubuntu14.7 and qemu-kvm 1.2.0+noroms-0ubuntu7 (source from quantal, built for Precise with pbuilder.) I attempted to build qemu-1.3.0 debs from source to test, but libvirt seems to have an issue with it that I haven't been able to track down yet.

 I'm seeing a performance degradation after live migration on Precise, but not Lucid. These hosts are managed by libvirt (tested both 0.9.8-2ubuntu17 and 1.0.0-0ubuntu4) in conjunction with OpenNebula. I don't seem to have this problem with lucid guests (running a number of standard kernels, 3.2.5 mainline and backported linux-image-3.2.0-35-generic as well.)

I first noticed this problem with phoronix doing compilation tests, and then tried lmbench where even simple calls experience performance degradation.

I've attempted to post to the kvm mailing list, but so far the only suggestion was it may be related to transparent hugepages not being used after migration, but this didn't pan out. Someone else has a similar problem here - http://thread.gmane.org/gmane.comp.emulators.kvm.devel/100592

qemu command line example: /usr/bin/kvm -name one-2 -S -M pc-1.2 -cpu Westmere -enable-kvm -m 73728 -smp 16,sockets=2,cores=8,threads=1 -uuid f89e31a4-4945-c12c-6544-149ba0746c2f -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/one-2.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew -no-kvm-pit-reinjection -no-shutdown -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive file=/var/lib/one//datastores/0/2/disk.0,if=none,id=drive-virtio-disk0,format=raw,cache=none -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -drive file=/var/lib/one//datastores/0/2/disk.1,if=none,id=drive-ide0-0-0,readonly=on,format=raw -device ide-cd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 -netdev tap,fd=23,id=hostnet0,vhost=on,vhostfd=25 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=02:00:0a:64:02:fe,bus=pci.0,addr=0x3 -vnc 0.0.0.0:2,password -vga cirrus -incoming tcp:0.0.0.0:49155 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5

Disk backend is LVM running on SAN via FC connection (using symlink from /var/lib/one/datastores/0/2/disk.0 above)

ubuntu-12.04 - first boot
==========================================
Simple syscall: 0.0527 microseconds
Simple read: 0.1143 microseconds
Simple write: 0.0953 microseconds
Simple open/close: 1.0432 microseconds

Using phoronix pts/compuational
ImageMagick - 31.54s
Linux Kernel 3.1 - 43.91s
Mplayer - 30.49s
PHP - 22.25s

ubuntu-12.04 - post live migration
==========================================
Simple syscall: 0.0621 microseconds
Simple read: 0.2485 microseconds
Simple write: 0.2252 microseconds
Simple open/close: 1.4626 microseconds

Using phoronix pts/compilation
ImageMagick - 43.29s
Linux Kernel 3.1 - 76.67s
Mplayer - 45.41s
PHP - 29.1s

I don't have phoronix results for 10.04 handy, but they were within 1% of each other...

ubuntu-10.04 - first boot
==========================================
Simple syscall: 0.0524 microseconds
Simple read: 0.1135 microseconds
Simple write: 0.0972 microseconds
Simple open/close: 1.1261 microseconds

ubuntu-10.04 - post live migration
==========================================
Simple syscall: 0.0526 microseconds
Simple read: 0.1075 microseconds
Simple write: 0.0951 microseconds
Simple open/close: 1.0413 microseconds