[Qemu-devel] Re: [PATCH 10/12] kvm: enable smp > 1

[Udo Lembke]

Avi Kivity schrieb:
> On 05/19/2010 11:02 PM, Udo Lembke wrote:
> > > Unrelated, what are your smp issues?
> >
> > If i use one cpu i got a good io-performance:
> > e.g. over 500MB/s at the profile "install" of the io-benchmark 
> > h2benchw.exe.
> > ( aio=threads | SAS-Raid-0 | 
> > ftp://ftp.heise.de/pub/ct/ctsi/h2benchw.zip | hwbenchw.exe -p -w 
> > iotest 0)
> > The same test but with two cpus gives results between 27 and 298 MB/s!
> >
> > Also in real life it's noticeable not only with an benchmark. I use a 
> > win-vm with two cpu for postscript-ripping and have a performance 
> > drop due to the bad io.
Hi,
> What's your block device model?  virtio or ide?
in the test described before i used virtio, but the same happens with 
ide (but of course slightly different values).
> What does cpu usage look like on guest or host?
On the guest it's looks like the io-process flap between the cpus. 
Windows show both cpus together are around 65% (less or more) , but if 
one CPU-usage rise, the other drop.
On the host:
 PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
5386 root      20   0 1160m 1.0g 1552 R  109 13.5   1:23.58 kvm

The guest is a win-xp, but the same happens in real life on a win2003.

Udo

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