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

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

Academically, this may not be a bug, but I think its
fair to argue that domain0 should be a special case
for using "slack" CPU time, at least by default.

Indeed, an argument could/should be made that the
whole concept of an idle domain should go away
entirely.

Dan 

> -----Original Message-----
> From: Bin Ren [mailto:bin.ren@xxxxxxxxx] 
> Sent: Friday, July 08, 2005 1:07 PM
> To: Andrew Theurer
> Cc: Magenheimer, Dan (HP Labs Fort Collins); 
> xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Re: IDLE domain is scheduled more than dom0
> 
> 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 2.6.11.12, domU sees significant drop in network throughputs
> (~40% less!) I'm interested in whether other people encounter similar
> situations, especially on SMP machines.
> 
> Cheers,
> Bin
> 
> 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
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> >
> 

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