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Re: [Xen-devel] xm speed



James Harper wrote:
Is it like this even when you haven't got a domain in a bad
state?


I think so, although I've never actually timed it before.


Of the 1.4s of CPU, consumed, 1.2s seems to being accounted to
'xm', so we can assume that 'xend' is consuming the other
0.2. What's odd about this is that _xend_ is the guy that's
actually doing most of the work -- xm just does an RPC to it.

Anyhow, it might be more informative to figure out where the
difference between real time and CPU time is coming
from. Presumably xm/xend is blocking on IO. I wander if running
an strace on xm and/or xend might be informative.

BTW: how are you accessing your root file system (local disk,
NFS) etc?


Root filesystem in dom0 is a local raid array, albeit a very slow one.
The disk appears to do a fair bit of chugging when I run it, although
I'm not normally near the box.

This could be your problem - xm is going to load quite a few python
classes to make the call.


After a checkout and rebuild just now, it appears to be much faster!

Name              Id  Mem(MB)  CPU  State  Time(s)  Console
Domain-0           0      123    0  r----     81.8
gaia2              1      126    0  -b---     22.0    9601

real    0m2.254s
user    0m1.100s
sys     0m0.090s
Name              Id  Mem(MB)  CPU  State  Time(s)  Console
Domain-0           0      123    0  r----     83.9
gaia2              1      126    0  -b---     22.1    9601

real    0m2.544s
user    0m1.110s
sys     0m0.100s
Name              Id  Mem(MB)  CPU  State  Time(s)  Console
Domain-0           0      123    0  r----     86.5
gaia2              1      126    0  -b---     22.2    9601

real    0m2.465s
user    0m1.060s
sys     0m0.140s
Name              Id  Mem(MB)  CPU  State  Time(s)  Console
Domain-0           0      123    0  r----     88.6
gaia2              1      126    0  -b---     22.3    9601

real    0m2.529s
user    0m1.060s
sys     0m0.150s
Name              Id  Mem(MB)  CPU  State  Time(s)  Console
Domain-0           0      123    0  r----     91.1
gaia2              1      126    0  -b---     22.4    9601

real    0m2.371s
user    0m1.080s
sys     0m0.130s
Name              Id  Mem(MB)  CPU  State  Time(s)  Console
Domain-0           0      123    0  r----     93.3
gaia2              1      126    0  -b---     22.5    9601

real    0m2.326s
user    0m1.130s
sys     0m0.130s

2 seconds is still a bit slow considering what it is actually doing, but
better than 10.

James



Anyway, here are some more data points. I ran xm list and compared it
with wget to see what the difference was. I only show the times once,
but they were consistently repoducible.

Timing of 'xm list':
mjw@wray-m-4 1028> time xm list
Name              Id  Mem(MB)  CPU  State  Time(s)  Console
Domain-0           0      123    0  r----     13.1

real    0m0.178s
user    0m0.160s
sys     0m0.000s

Timing of getting python to print hello:
mjw@wray-m-4 1034> time python -c 'print "Hello"'
Hello

real    0m0.016s
user    0m0.010s
sys     0m0.000s

So xm's real work takes about 0.16 s (160ms).

For a comparison let's try getting the domain list with wget:

mjw@wray-m-4 1009> echo $http_proxy
http://15.144.59.5:8088
mjw@wray-m-4 1010> unset http_proxy
mjw@wray-m-4 1014> time wget -q http://localhost:8000/xend/domain/

real    0m0.013s
user    0m0.010s
sys     0m0.000s

This takes 0.013s (13ms) so the time is spent in xm not xend.

mjw@wray-m-4 1042> uname -a
Linux wray-m-4.hpl.hp.com 2.4.27-xen0 #1 Tue Sep 14 12:00:35 BST 2004 i686 i686 i386 GNU/Linux
mjw@wray-m-4 1043> cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Xeon(TM) CPU 2.80GHz
stepping        : 9
cpu MHz         : 2791.039
cache size      : 512 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid
bogomips        : 5570.56

Mike Wray




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