Re: [rvm-research] Scheduling a new Garbage Collection Phase

Robin,

       Ah, I get it, so it schedules it after _every_ CLOSURE. That my
problem; what I really want to do is schedule it after all the CLOSURE
phases are complete, and all reachable objects are marked. So I think I
want to schedule after refTypeClosurePhase?

      --Nathan




On Mon, Jul 8, 2013 at 8:58 PM, Robin Garner <[email protected]> wrote:

> On 09/07/13 09:48, Nathan Ricci wrote:
> >     I'm implementing a garbage collector, called (for now) the
> > "Control Collector". I've based it on the mark sweep collector, and
> > the classes are called "GCControl", GCControlCollector, etc.
> >
> >     As part of this, I'm trying to add a new collection phase, and I
> > want to divide some of the work between multiple threads. I seem to
> > have misunderstood how to do this, however, since in the
> > GCControlCollector#collectionPhase, I see the same worker ordinal
> > enter the new phase multiple times in a garbage collection.
> >
> >      Do I even have the right idea? Is it the case that in a
> > Collector, I should only see a given phaseID once per worker ordinal
> > (as returned by ParallelCollector#parallelWorkerOrdinal()), and the
> > worker ordinals have a one-to-one correspondence to threads?
> You have the right idea - this is the intention.
>
> Bear in mind that the phase CLOSURE is invoked 3 times in a Simple
> collection, so you should see your control closure invoked 3 times per
> GC thread.
>
> What do you see at GC verbosity level 7 with 1 GC thread ?  Two threads ?
>
> The logic for scheduling phases is in org.mmtk.plan.Phase - it might be
> helpful to write a pretty-printer for complex phases so that you can
> statically check the resulting structure after your modification.  Some
> if the login in the Phase class is pretty byzantine, but
> processPhaseStack is where most of it happens, and this is fairly
> straightforward.
>
> Hope this helps,
> Robin
> >
> >      Some code is below. Thanks for any help.
> >
> >            --Nathan Ricci
> >               Tufts University
> >
> > I create and schedule the phase in the plan:
> >
> > public class GCControl extends MS {
> > ...
> >   public static final short CONTROL_CLOSURE =
> > Phase.createSimple("GCControl.control_closure");
> >   protected static final short controlClosurePhase =
> > Phase.createComplex("GCControl.control_closure_complex",
> >
> >     null,
> >
> >     Phase.scheduleGlobal(CONTROL_CLOSURE),
> >
> >     Phase.scheduleCollector(CONTROL_CLOSURE));
> >
> > public GCControl() {
> >     super();
> >   this.insertPhaseAfter(Phase.scheduleCollector(PREPARE),
> >    i                         Phase.scheduleComplex(controlPhase));
> >
> >     this.insertPhaseAfter(Phase.scheduleCollector(CLOSURE),
> > Phase.scheduleComplex(controlClosurePhase));
> >
> >        ...
> > }
> >
> > Here is the collectionPhase method from the GCControlCollector:
> >
> > public void collectionPhase(short phaseId, boolean primary) {
> >
> >  if (phaseId == GCControl.CONTROL_CLOSURE) {
> >    Log.write("GCControlCollector: collectionPhase: CONTROL_CLOSURE
> > phase: ordinal ");
> >    Log.write(parallelWorkerOrdinal());
> >   ...
> >    return;
> >  }
> >   ...
> >  super.collectionPhase(phaseId, primary);
> >   }
> >
> >
> > I end up seeing from those log messages that the CONTROL_CLOSURE phase
> > comes up multiple times with the same worker ordinal, even within a
> > garbage collection.
> >
> >
> >
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