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

[Bin Ren <bin.ren@xxxxxxxxx>]

Default SEDF settings. I have never changed any SEDF parameters. It's
uniprocessor. With some netback driver instrumentation, I find out
that SEDF preempts a lot more aggresive even than BVT. For example,
when dom1 is sending data to an external host, during each context
switch the number of pages dom0 takes off the Tx ring and delivers to
the NIC always (yes, 100% of the time) fall between 1-8. With BVT, 70%
of batch-sizes fall between 1-8 with the rest scattered around 20-40.
In short, there are too frequent preemption/context switches with SEDF
on uniprocessors.

- Bin

On 7/9/05, Stephan Diestelhorst <sd386@xxxxxxxxx> wrote:
> >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.
> >
> >
> >
> >
> Mhmhm, this is interesting, what are the timing parameters for your domains?
> 
> Thanks,
>    Stephan
> 
> >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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> >>
> >>
> >>
> >
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> >
> >
> 
>

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