Re: [Xen-devel] xm speed

[Mike Wray <mike.wray@xxxxxxxxxx>]

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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