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Re: [Xen-users] xen scheduling

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] xen scheduling
From: Gyimesi Ákos <gyimesi.akos@xxxxxxxxxxxxx>
Date: Thu, 07 Sep 2006 12:23:20 +0200
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Yesterday I rebooted the machine with option sched=bvt and now it seems to work perfectly. Did anybody else experience such issues with the sedf scheduler?


Gyimesi Ákos írta:
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, and of course, xen-utils with the same version.


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