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

  • To: "Stephan Diestelhorst" <sd386@xxxxxxxxx>
  • From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
  • Date: Mon, 11 Jul 2005 21:19:09 +0800
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Mon, 11 Jul 2005 13:18:01 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcWGC1vFYdHeNuQWQR2mDV16ph5V2wADBOcA
  • Thread-topic: IDLE domain is scheduled more than dom0

>From: sd386@xxxxxxxxxxxxxxxx [mailto:sd386@xxxxxxxxxxxxxxxx] On
>Behalf Of Stephan Diestelhorst
>Sent: Monday, July 11, 2005 7:26 PM
>> Not sure whether that strange coming from the fact that IDLE is also
>> initialized with period as WEIGHT_PERIOD(100ms)?
>This will not matter, and in fact add_domain will not get called for
the idle

Ah, yes, slice of IDLE is always 0, which means arbitration will take
effect on every tick when current is IDLE.

>> >b) set inf->slice = MILLIESECS(20);
>Okay, thanks for your investigation!
>The thing is that the idle domain IS the lowest prioritised domain in
>system! So if you set the EXTRA_AWARE flag, it should almost never get
>scheduled. The only case when this will happen is when dom0 does I/O,
>is treated differently whether it occurs in EDF-time or in extra-time.
I will
>have a closer look at this, as this behaviuor is not acceptable.

And one thing I'd like you to know is, my test environment is with
XEN/VTI domain0, which is whole unmodified one without any explicit
request to do_block. So actually within this model, you can consider
Dom0 as always runable... Not sure this different behavior as xen0 will
cause any issue in sedf scheduler which, however can be considered as an
extreme example for IDLE never to be scheduled. ;-)


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