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

[Udo Lembke <ulembke@polarzone.de>]

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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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