[Xen-users] xen scheduling

[Gyimesi Ákos <gyimesi.akos@xxxxxxxxxxxxx>]

Hi all,

I have xen 3.0.2 installed on our server with 5+1 domains running. The 
CPU load is usually below 1 on all domains, but while 2 of them runs 
very well (including dom0), all others have extermely poor performance. 
After some research I found that these domains simply don't receive 
enough CPU time - I wrote a small script which does some calculations 
and the results speak for themselves:
root@sql:~# time perl proba.pl
real    0m4.762s
user    0m4.724s
sys     0m0.000s

root@mail:~# time perl proba.pl
real    0m21.299s
user    0m0.168s
sys     0m0.004s
(I sent a Ctrl-C to 21 seconds)

I also found out that if I shutdown sql and then I start mail, mail will 
be the fast domain, so timing only depends on the sequence I start the 
domains (all domains have the same kernel).
I assumed that this should be a scheduling problem, so I tried to adjust 
the sched-sedf parameters. But no matter what I pass to xm sched-sedf, 
parameters remain the same:
root@evermind:/var/log# xm sched-sedf
Name                              ID Period(ms) Slice(ms) Lat(ms) Extra 
Weight
Domain-0                           0      20.0      15.0     0.0      
1      0
devel                             19     100.0       0.0     0.0      
1      0
mail                              16     100.0       0.0     0.0      
1      0
privateweb                        17     100.0       0.0     0.0      
1      0
publicweb                          5     100.0       0.0     0.0      
1      0
sql                               18     100.0       0.0     0.0      
1      0
I even tried to assign 2 vcpus to the slow host (I have a dual-core 
Opteron), but that didn't help either.
Any ideas?

I'm using xen-hypervisor-3.0-i386-pae 3.0.2+hg9697-0bpo1 from the 
backports.org package with kernel 2.6.16.24, and of course, xen-utils 
with the same version.
Thanks,
gyim


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