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Re: [Xen-devel] Re: IDLE domain is scheduled more than dom0

To: Andrew Theurer <habanero@xxxxxxxxxx>
Subject: Re: [Xen-devel] Re: IDLE domain is scheduled more than dom0
From: Bin Ren <bin.ren@xxxxxxxxx>
Date: Fri, 8 Jul 2005 20:06:41 +0100
Cc: Dan Magenheimer <dan.magenheimer@xxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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I think it's quite likely that by default SEDF doesn't allow  domains
to use slack CPU time, i.e. non  work-conserving. Each domain is given
an absolute percentage of the total CPU time. Try use command "xm sedf
dom-id 0 0 0 1 0" to give a domain access to slack CPU time. Hopefully
this could restore the performance.

BTW, on my uniprocessor test machine with latest xen-unstable,
xenlinux, domU sees significant drop in network throughputs
(~40% less!) I'm interested in whether other people encounter similar
situations, especially on SMP machines.


On 7/8/05, Andrew Theurer <habanero@xxxxxxxxxx> wrote:
> On Friday 08 July 2005 11:33, Andrew Theurer wrote:
> > On Friday 08 July 2005 09:53, Dan Magenheimer wrote:
> > > >   Shouldn't IDLE domain not be scheduled for most time? Because
> > > > idle task will call into PAL for power save on XEN/IA64, the
> > > > performance is really, really bad to boot Dom0. The net effect is
> > > > about ten times slower. After adding "sched=bvt", everything back
> > > > to normal.
> > >
> > > If the sedf scheduler is scheduling the idle domain when
> > > domain0 is runnable, surely this is affecting performance
> > > on x86 also and is a bug that should be fixed?
> > >
> > > Has anyone done any performance testing (on x86) since
> > > sedf was checked in as the default?
> >
> > Just tried launching some cpu bound tasks in dom0, and I get only 75%
> > cpu util for dom0.  I'll try the other domain scheduler and see if it
> > clears it up.
> OK, just confirmed bvt works as expected in ia32.
> -Andrew
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