On Fri, Mar 04, 2016 at 11:14:44AM -0500, Lars Kellogg-Stedman wrote:
I was interested in using 'virsh vol-upload' and 'virsh vol-download', rather than mucking about directly with the filesystem. But while simply copying the image is relatively quick:
# ls -l /var/lib/libvirt/images/centos-7-cloud.qcow2 -rw-r--r--. 1 qemu qemu 1004994560 Apr 15 2015 centos-7-cloud.qcow2 # time cp /var/lib/libvirt/images/centos-7-cloud.qcow2 /tmp/myimage.qcow2 real 0m10.829s user 0m0.024s sys 0m1.668s
Trying to do the same thing with `virsh vol-download` is glacial:
# time virsh vol-download --pool default centos-7-cloud.qcow2 /tmp/myimage.qcow2
I killed it after 10 minutes:
real 10m20.775s user 10m19.451s sys 0m1.887s
After which is was about halfway through:
# ls -l /tmp/myimage.qcow2 -rw-r--r--. 1 root root 564920248 Mar 4 11:11 /tmp/myimage.qcow2
What is up with that?
What version of libvirt ? We had an unfortunate implementation mistake which caused us to waste tonnes of time in memmove(). versions since 1.2.19 have a fix that addresses it commit d9c9e138f22c48626f719f880920e04c639e0177 Author: Ossi Herrala <oherrala@gmail.com> Date: Mon Jul 20 12:44:32 2015 +0000 rpc: Fix slow volume download (virsh vol-download) Use I/O vector (iovec) instead of one huge memory buffer as suggested in https://bugzilla.redhat.com/show_bug.cgi?id=1026137#c7. This avoids doing memmove() to big buffers and performance doesn't degrade if source (virNetClientStreamQueuePacket()) is faster than sink (virNetClientStreamRecvPacket()). Resolves: http://bugzilla.redhat.com/1026137 Signed-off-by: Martin Kletzander <mkletzan@redhat.com> Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|