Re: Lost of performance over AMD-V with KVM?

[Victor fernandez <Victormanuel.fernandez@usc.es>]

Hi Gleb,

     you were right, we update the qemu-kvm to 1.0 and now
     the S.L. instance start with new cpu flags (for instance: 
3dnowext,3dnow).

     But we have bad performance still, around 17% of lost in
     our AMD processors. Let me explain better, we are running
     three different hight energy physic softwares. And in 2 of them
     we don't have any problem with the performances, 4-5% of lost.
     But in the other one (GAUSS, LHCb software), and only in
     AMD-V virtualization we have arount 17%-33% lost performance
     depending on the processor number. But Gauss software in
     Intel processor are running with an acceptable performance.

     And we suspected that could be due to cpu flags, but now we are not
     sure about that because now 3dnowext,3dnow are included
     and the performances are still bad. But these flags are not yet 
included
     with qemu-kvm_1.0.

 > ht > rdtscp > constant_tsc > nopl > nonstop_tsc > amd_dcm > monitor > 
extapic > ibs > skinit > wdt > nodeid_msr > hw_pstate > lbrv > svm_lock 
 > pausefilter

     - Do you think that these flags could be the problem?
     - Do you have any idea what could it be?

     Thanks in advance Gleb,
         Víctor Fdez.


El 09/07/13 18:08, Gleb Natapov escribió:
> On Tue, Jul 09, 2013 at 05:30:26PM +0200, Victor fernandez wrote:
>> Hi Gleb,
>>
>>      root@vfalbor-desktop:~# uname -a
>> *Linux vfalbor-desktop 2.6.32-24-generic *#43-Ubuntu SMP Thu Sep 16
>> 14:58:24 UTC 2010 x86_64 GNU/Linux
>>
>>      root@vfalbor-desktop:~# dpkg --list | grep qemu
>>      ii  qemu-common *0.12.3+noroms-0ubuntu9.21 * qemu common
>> functionality (bios, documentati
>>      ri  qemu-kvm *0.12.3+noroms-0ubuntu9.21*
>> Full virtualization on i386 and amd64 hardwa
>>
> Ugh, those are ancient and vendor packages. I thought you were running
> Scientific Linux 6 as a host too which also has vendor specific
> packages, but at least something that I can easily look into :)
> Can you reproduce with upstream kernel/qemu? If it works on upstream you
> can open bug in Ubuntu.
>
>>      One of the things that we did, we try to update libvirt to the
>> last versions
>>      because we are using for our cloud the version of ubuntu 10.04 and the
>>      last stable version of libvirt was 0.7.5-5ubuntu27.23, but when
>> we try to
>>      get the capabilities, we get the following:
> This is definitely not libvirt fault. This is either kernel or qemu.
> Looking into git history 3dnow/3dnowext support was introduce into the
> kernel kvm component before 2.6.32 though.
>
>>      root@vfalbor-desktop:~/# virsh capabilities | grep 3dnow
>>        <feature name='*3dnowprefetch*'/>
>>      root@vfalbor-desktop:~/#
>>
>>      but in the cpu_map.xml file we find the 3dnow and 3dnowext for
>> our architecture:
>>
>>      root@vfalbor-desktop:~/# cat /usr/share/libvirt/cpu_map.xml |
>> grep 3dnow
>>              <feature name='*3dnowext*'> <!-- CPUID_EXT2_3DNOWEXT -->
>>              <feature name='3dnow'> <!-- CPUID_EXT2_3DNOW -->
>>              <feature name='3dnowprefetch'> <!--
>> CPUID_EXT3_3DNOWPREFETCH -->
>>
>>      Thanks Gleb,
>>          Víctor Fdez.
>>
>> El 09/07/13 17:16, Gleb Natapov escribió:
>>> On Tue, Jul 09, 2013 at 05:07:57PM +0200, Victor fernandez wrote:
>>>> Yep,
>>>>
>>>>      -> this is for the host:
>>>>
>>>>      root@vfalbor-desktop:~# cat /proc/cpuinfo | grep flags | uniq
>>>>      flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr
>>>> pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx
>>>> mmxext fxsr_opt pdpe1gb rdtscp lm 3dnowext 3dnow constant_tsc
>>>> rep_good nonstop_tsc extd_apicid amd_dcm pni monitor cx16 popcnt
>>>> lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse
>>>> 3dnowprefetch osvw ibs skinit wdt nodeid_msr
>>>>
>>>>      -> this is for the VM:
>>>>      [root@sl6 ~]# cat /proc/cpuinfo | grep flags | uniq
>>>>      flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr
>>>> pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext
>>>> fxsr_opt pdpe1gb lm rep_good extd_apicid pni cx16 popcnt lahf_lm
>>>> cmp_legacy cr8_legacy abm sse4a misalignsse 3dnowprefetch
>>>>
>>> Hmm, what is your kernel and qemu versions?
>>>
>>>> El 09/07/13 17:00, Gleb Natapov escribió:
>>>>> On Tue, Jul 09, 2013 at 04:57:13PM +0200, Victor fernandez wrote:
>>>>>>      2.- with the "-cpu host" parameter:
>>>>>>
>>>>>> /usr/bin/kvm *-cpu host* -m 2048 -smp 1 -name i-2-11-VM -monitor
>>>>>> telnet:127.0.0.1:9941,server,nowait -boot c /mnt/b07f7f29-7b9b-3d4b-b170-77876d10e7b1/134bc689-1207-487c-ae95-6c0dc2e0f285
>>>>>> -parallel none -usb -usbdevice tablet -vnc :0 -vga cirrus -net
>>>>>> nic,macaddr=06:00:90:00:00:08,vlan=0,model=e1000,name=e1000.0 -net
>>>>>> tap,script=/usr/bin/qemu-ifup,vlan=0,name=tap.0
>>>>>>
>>>>> With this command line can you provide output of /proc/cpuinfo on the
>>>>> host and the guest?
>>>>>
>>>>> --
>>>>> 			Gleb.
>>>>> --
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>>> --
>>> 			Gleb.
> --
> 			Gleb.