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

[Avi Kivity]

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.

What's your block device model?  virtio or ide?

What does cpu usage look like on guest or host?

--
Do not meddle in the internals of kernels, for they are subtle and quick to 
panic.