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

[Erik Jacobson <erikj@sgi.com>]

Hello.  I'll top-post since the quoted text is just for reference.

Sorry the follow-up testing took so long.  We're very low on 5500/Nehalem
resources at the moment and I had to track down lots of stuff before
getting to the test.

I ran some tests on a 2-socket, 8-core system.  I wasn't pleased with the
results for a couple reasons.  One, the issue of it being twice as slow
as the host with no guest was still present.

However, in trying to make use of this system using Fedora 11, I ran in to
several issues not directly related to virtualization.  So these test runs
have that grain of salt.  Example issues...
 * Node ordering is not sequential (Ie /sys/devices/sysstem/node/node0 and
   node2, but no node 1).  This caused tools based on libvirt and friends
   to be unhappy.  I worked around this by using qemu-kvm by hand directly.
   we found an LKML posting to address this issue; I didn't check if it made
   it in yet.
 * All cores show up as being associated with the first node (node0) even
   though half should be associated with the 2nd node (still researching that
   some).
 * In some of the timing runs on this system, the "real time" reported by
   the time command was off by 10 to 11 times.  Issues were found in
   the messages file that seemed to relate to this including HUGE time
   adjustments by NTP and kernel hrtimer 'interrupt too slow' messages.
   This specific problem seems to be intermittent.
 * None of the above problems were observed in 8-core/2-socket non-5500/
   Nehalem systems.  Of course, 2-socket non-Nehalem systems do not have
   multiple nodes listed under /sys.
 * I lose access to the resource today but can try to beg and plead again
   some time next week if folks have ideas to try.  Let me know.

So those are the grains of salt.  I've found that, when doing the timing by
hand instead of using the time command, the build time seems to be around
10 to 12 minutes.  I'm not sure how trustworthy the output from the time
command are in these trials.  In any event, that's still more than double
for host alone with no guests.

System:
SGI XE270, 8-core, Xeon X5570 (Nehalem), Hyperthreading turned off
Supermicro model: X8DTN
Disk1: root disk 147GB ST3146855SS 15K 16MB cache SAS
Disk2: work area disk 500GB HDS725050KLA360  7200rpm 16MB cache SATA
Distro: Everything Fedora11+released updates
Memory: 8 gb in 2048 DDR3 1066 MHZ 18JSF25672PY-1G1D1 DIMMs

Only Fedora11 was used (host and guest where applicable).
The first timing weirdness was done on a F11 guest with no updates
applied.  I later applied the updates and the timings seemed to get
worse, although I don't trust the values any more.

F11+released updates has these versions:
kernel-2.6.29.4-167.fc11.x86_64
qemu-kvm-0.10.5-2.fc11.x86_64


Test, as before, was simply this for a kernel build.  The .config file has
plenty of modules configured.
time (make -j12 && make -j12 modules)



host only, no guest, baseline
-----------------------------
trial 1:
real	5m44.823s
user	28m45.725s
sys	5m46.633s

trial 2:
real	5m34.438s
user	28m14.347s
sys	5m41.597s


guest, 8 vcpu, 4096 mem, virtio, no cache param, disk device supplied in full
-----------------------------------------------------------------------------
trial 1:
real	125m5.995s
user	31m23.790s
sys	9m17.602s


trial 2 (changed to 7168 mb memory for the guest):
real	120m48.431s
user	14m38.967s
sys	6m12.437s


That's real strange...  The 'time' command is showing whacked out results.

I then watched a run by hand and counted it at about 10 minutes.  However,
this third run had the proper time!  So whatever the weirdness is, it doesn't
happen every time:

real	9m49.802s
user	24m46.009s
sys	8m10.349s

I decided this could be related to ntp running as I saw this in messages:
Jun 18 16:34:23 localhost ntpd[1916]: time reset -0.229209 s
Jun 18 16:34:23 localhost ntpd[1916]: kernel time sync status change 0001
Jun 18 16:40:17 localhost ntpd[1916]: synchronized to 128.162.244.1, stratum 2

and earlier:

Jun 18 16:19:09 localhost ntpd[1916]: synchronized to 128.162.244.1, stratum 2
Jun 18 16:19:09 localhost ntpd[1916]: time reset +6609.851122 s
Jun 18 16:23:39 localhost ntpd[1916]: synchronized to 128.162.244.1, stratum 2
Jun 18 16:24:04 localhost kernel: hrtimer: interrupt too slow, forcing clock min delta to 62725995 ns


I then installed all F11 updates in the guest and tried again (host had
updates all along).  I got these strange results, strange because of the
timing difference.  I didn't "watch a non-computer clock" for these.

Timing from that was:
trial 1:
real	16m10.337s
user	28m27.604s
sys	9m12.772s

trial 2:
real	11m45.934s
user	25m4.432s
sys	8m2.189s


Here is the qemu-kvm command line used.  The -m was for the first run was
4096, and it was 7168 for the other runs.

# /usr/bin/qemu-kvm -M pc -m 4096 -smp 8 -name f11-test -uuid b7b4b7e4-9c07-22aa-0c95-d5c8a24176c5 -monitor pty -pidfile /var/run/libvirt/qemu//f11-test.pid -drive file=/foo/f11/Fedora-11-x86_64-DVD.iso,if=virtio,media=cdrom,index=2 -drive file=/var/lib/libvirt/images/f11-test.img,if=virtio,index=0,boot=on -drive file=/dev/sdb,if=virtio,index=1 -net nic,macaddr=54:52:00:46:48:0e,model=virtio -net user -serial pty -parallel none -usb -usbdevice tablet -vnc cct201:1 -soundhw es1370 -redir tcp:5555::22


/proc/cpuinfo is pasted after the test results.




# cat /proc/cpuinfo
processor	: 0
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5570  @ 2.93GHz
stepping	: 5
cpu MHz		: 1600.000
cache size	: 8192 KB
physical id	: 0
siblings	: 4
core id		: 0
cpu cores	: 4
apicid		: 0
initial apicid	: 0
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 lahf_lm ida tpr_shadow vnmi flexpriority ept vpid
bogomips	: 5865.69
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management:

processor	: 1
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5570  @ 2.93GHz
stepping	: 5
cpu MHz		: 1600.000
cache size	: 8192 KB
physical id	: 0
siblings	: 4
core id		: 1
cpu cores	: 4
apicid		: 2
initial apicid	: 2
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 lahf_lm ida tpr_shadow vnmi flexpriority ept vpid
bogomips	: 5865.76
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management:

processor	: 2
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5570  @ 2.93GHz
stepping	: 5
cpu MHz		: 1600.000
cache size	: 8192 KB
physical id	: 0
siblings	: 4
core id		: 2
cpu cores	: 4
apicid		: 4
initial apicid	: 4
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 lahf_lm ida tpr_shadow vnmi flexpriority ept vpid
bogomips	: 5823.99
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management:

processor	: 3
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5570  @ 2.93GHz
stepping	: 5
cpu MHz		: 1600.000
cache size	: 8192 KB
physical id	: 0
siblings	: 4
core id		: 3
cpu cores	: 4
apicid		: 6
initial apicid	: 6
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 lahf_lm ida tpr_shadow vnmi flexpriority ept vpid
bogomips	: 5865.76
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management:

processor	: 4
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5570  @ 2.93GHz
stepping	: 5
cpu MHz		: 1600.000
cache size	: 8192 KB
physical id	: 1
siblings	: 4
core id		: 0
cpu cores	: 4
apicid		: 16
initial apicid	: 16
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 lahf_lm ida tpr_shadow vnmi flexpriority ept vpid
bogomips	: 5865.80
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management:

processor	: 5
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5570  @ 2.93GHz
stepping	: 5
cpu MHz		: 1600.000
cache size	: 8192 KB
physical id	: 1
siblings	: 4
core id		: 1
cpu cores	: 4
apicid		: 18
initial apicid	: 18
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 lahf_lm ida tpr_shadow vnmi flexpriority ept vpid
bogomips	: 5865.80
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management:

processor	: 6
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5570  @ 2.93GHz
stepping	: 5
cpu MHz		: 1600.000
cache size	: 8192 KB
physical id	: 1
siblings	: 4
core id		: 2
cpu cores	: 4
apicid		: 20
initial apicid	: 20
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 lahf_lm ida tpr_shadow vnmi flexpriority ept vpid
bogomips	: 5865.80
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management:

processor	: 7
vendor_id	: GenuineIntel
cpu family	: 6
model		: 26
model name	: Intel(R) Xeon(R) CPU           X5570  @ 2.93GHz
stepping	: 5
cpu MHz		: 1600.000
cache size	: 8192 KB
physical id	: 1
siblings	: 4
core id		: 3
cpu cores	: 4
apicid		: 22
initial apicid	: 22
fpu		: yes
fpu_exception	: yes
cpuid level	: 11
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 lahf_lm ida tpr_shadow vnmi flexpriority ept vpid
bogomips	: 5865.79
clflush size	: 64
cache_alignment	: 64
address sizes	: 40 bits physical, 48 bits virtual
power management:



On Sun, Jun 14, 2009 at 12:33:06PM +0300, Avi Kivity wrote:
> Erik Jacobson wrote:
>> We have been trying to test qemu-kvm virtual machines under an IO load.
>> The IO load is quite simple: A timed build of the linux kernel and modules.
>> I have found that virtual machines take more than twice as long to do this
>> build as the host.  It doesn't seem to matter if I use virtio or not,  Using
>> the same device and same filesystem, the host is more than twice as fast.
>>
>> We're hoping that we can get some advice on how to address this issue.  If
>> there are any options I should add for our testing, we'd appreciate it.  I'm
>> also game to try development bits to see if they make a difference.  If it
>> turns out "that is just the way it is right now", we'd like to know that
>> too.
>>
>> For these tests, I used Fedora 11 as the virtualization server.  I did this
>> because it has recent bits.  I experimented with SLES11 and Fedora11 guests.
>>
>> In general, I used virt-manager to do the setup and launching.  So the
>> qemu-kvm command lines are based on that (and this explains why they are
>> a bit long).  I then modified the qemu-kvm command line to perform other
>> variations of the test.  Example command lines can be found at the end of
>> this message.
>>
>> I performed tests on two different systems to be sure it isn't related to
>> specific hardware.
>>   
>
> What is the host cpu type?  On pre-Nehalem/Barcelona processors kvm has  
> poor scalability in mmu intensive workloads like kernel builds.
>
> -- 
> error compiling committee.c: too many arguments to function
-- 
Erik Jacobson - Linux System Software - SGI - Eagan, Minnesota