Re: Windows Server 2008R2 KVM guest performance issues

[Brian Rak <brak@gameservers.com>]

On 8/27/2013 3:18 AM, Paolo Bonzini wrote:
> Il 26/08/2013 21:15, Brian Rak ha scritto:
>> Samples: 62M of event 'cycles', Event count (approx.): 642019289177
>>   64.69%  [kernel]                    [k] _raw_spin_lock
>>    2.59%  qemu-system-x86_64          [.] 0x00000000001e688d
>>    1.90%  [kernel]                    [k] native_write_msr_safe
>>    0.84%  [kvm]                       [k] vcpu_enter_guest
>>    0.80%  [kernel]                    [k] __schedule
>>    0.77%  [kvm_intel]                 [k] vmx_vcpu_run
>>    0.68%  [kernel]                    [k] effective_load
>>    0.65%  [kernel]                    [k] update_cfs_shares
>>    0.62%  [kernel]                    [k] _raw_spin_lock_irq
>>    0.61%  [kernel]                    [k] native_read_msr_safe
>>    0.56%  [kernel]                    [k] enqueue_entity
> Can you capture the call graphs, too (perf record -g)?

Sure.  I'm not entire certain how to use perf effectively.  I've used 
`perf record`, then manually expanded the call stacks in `perf report`.  
If this isn't what you wanted, please let me know.

https://gist.github.com/devicenull/7961f23e6756b647a86a/raw/a04718db2c26b31e50fb7f521d47d911610383d8/gistfile1.txt

>> I've captured 20,000 lines of kvm trace output.  This can be found
>> https://gist.github.com/devicenull/fa8f49d4366060029ee4/raw/fb89720d34b43920be22e3e9a1d88962bf305da8/trace
> The guest is doing quite a lot of exits per second, mostly to (a) access
> the ACPI timer (b) service NMIs.  In fact, every NMI is reading the
> timer too and causing an exit to QEMU.
>
> So it is also possible that you have to debug this inside the guest, to
> see if these exits are expected or not.
Do you have any suggestions for how I would do this?  Given that the 
guest is Windows, I'm not certain how I could even begin to debug this.


Also, for that patch set I found, do I also need a patch for qemu to 
actually enable the new enlightenment? I haven't been able to find 
anything for qemu that matches that patch.  I did find 
http://www.mail-archive.com/kvm@vger.kernel.org/msg82495.html , but 
that's from significantly before the patchset, so I can't tell if that's 
still related.