Re: [Qemu-devel] [PATCH] migration: use XBZRLE only after bulk stage

[Peter Lieven]

On 01.03.2013 15:23, Eric Blake wrote:
> On 03/01/2013 07:13 AM, Peter Lieven wrote:
> > On 01.03.2013 15:08, Eric Blake wrote:
> > > On 03/01/2013 07:06 AM, Peter Lieven wrote:
> > > > > Do you have any benchmark numbers?  At any rate, the explanation seems
> > > > > sound, so a benchmark should show this.
> > > >
> > > > Do you have a particular test pattern in mind? If there is nothing
> > > > going on
> > > > in the VM XBZRLE will not be better than normal copy at all.
> > > >
> > > > Otherwise you will have N xbzrle misses and 0 xbzrle pages without the
> > > > patch
> > > > and 0 xbzrle misses and 0 xbzrle pages with the patch.
> > >
> > > How about a migration of a guest running the synthetic r/w load
> > > generator in docs/xbzrle.txt?
> > Good idea. I will leave max downtime and bandwidth at default values.
> >
> > Would you be happy with 1GB vRAM and 256MB page cache?
>
> Sure - just any run that you can do that shows before and after numbers,
> and that is described well enough to be a reproducible test.  Final
> statistics on the migration (pages transferred, cache hits and misses,
> etc) and time spent on the migration will hopefully show an improvement,
> but most important is that they do not show a regression.

just a quick test on my desktop:

~/git/qemu$ x86_64-softmmu/qemu-system-x86_64 -k de -enable-kvm -m 1024 -drive 
if=virtio,file=iscsi://172.21.200.31/iqn.2001-05.com.equallogic:0-8a0906-16470e107-713001aa6de511e0-001-test/0
 -vnc :1 -boot dc -monitor stdio

using ubuntu 12.04.1 desktop and the example from docs/xbzrle.txt

a) with the patch

(qemu) info migrate
capabilities: xbzrle: on
Migration status: completed
total time: 22185 milliseconds
downtime: 29 milliseconds
transferred ram: 706034 kbytes
remaining ram: 0 kbytes
total ram: 1057216 kbytes
duplicate: 108556 pages
normal: 175146 pages
normal bytes: 700584 kbytes
cache size: 67108864 bytes
xbzrle transferred: 3127 kbytes
xbzrle pages: 117811 pages
xbzrle cache miss: 18750
xbzrle overflow : 0

b) without the patch

(qemu) info migrate
capabilities: xbzrle: on
Migration status: completed
total time: 22410 milliseconds
downtime: 21 milliseconds
transferred ram: 721318 kbytes
remaining ram: 0 kbytes
total ram: 1057216 kbytes
duplicate: 105553 pages
normal: 179589 pages
normal bytes: 718356 kbytes
cache size: 67108864 bytes
xbzrle transferred: 630 kbytes
xbzrle pages: 21527 pages
xbzrle cache miss: 179589
xbzrle overflow : 0