Re: slow guest performance with build load, looking for ideas

[Avi Kivity <avi@redhat.com>]

On 07/02/2009 08:48 AM, Avi Kivity wrote:
>> HOST time (make -j12&&   make -j12 modules) with no guest running
>> ----------------------------------------------------------------
>> real    6m50.936s
>> user    29m12.051s
>> sys    5m50.867s
>>
>
> 35 minutes cpu run on 7 minutes real time, so scaling 1:7.  User time 
> almost the same, system time different but not enough to account for 
> the large difference in run time.
>
> I'm due to get my own Nehalem next week, I'll try to reproduce your 
> results here.
>

I reproduced this on a 2x4 barcelona, I get 6.6x scaling on the guest 
compared to your 7.2x on the host.  This is with a kvm.git host kernel.  
Once thing that changed is an improvement in cfq with multiple threads; 
try setting the host io scheduler for /dev/sdb to deadline (together 
with dropping -usbdevice tablet).


-- 
error compiling committee.c: too many arguments to function