1.1 --- a/src/share/vm/gc_implementation/parallelScavenge/psTasks.hpp Tue Nov 22 04:47:10 2011 -0500
1.2 +++ b/src/share/vm/gc_implementation/parallelScavenge/psTasks.hpp Tue Aug 09 10:16:01 2011 -0700
1.3 @@ -135,16 +135,63 @@
1.4 // OldToYoungRootsTask
1.5 //
1.6 // This task is used to scan old to young roots in parallel
1.7 +//
1.8 +// A GC thread executing this tasks divides the generation (old gen)
1.9 +// into slices and takes a stripe in the slice as its part of the
1.10 +// work.
1.11 +//
1.12 +// +===============+ slice 0
1.13 +// | stripe 0 |
1.14 +// +---------------+
1.15 +// | stripe 1 |
1.16 +// +---------------+
1.17 +// | stripe 2 |
1.18 +// +---------------+
1.19 +// | stripe 3 |
1.20 +// +===============+ slice 1
1.21 +// | stripe 0 |
1.22 +// +---------------+
1.23 +// | stripe 1 |
1.24 +// +---------------+
1.25 +// | stripe 2 |
1.26 +// +---------------+
1.27 +// | stripe 3 |
1.28 +// +===============+ slice 2
1.29 +// ...
1.30 +//
1.31 +// A task is created for each stripe. In this case there are 4 tasks
1.32 +// created. A GC thread first works on its stripe within slice 0
1.33 +// and then moves to its stripe in the next slice until all stripes
1.34 +// exceed the top of the generation. Note that having fewer GC threads
1.35 +// than stripes works because all the tasks are executed so all stripes
1.36 +// will be covered. In this example if 4 tasks have been created to cover
1.37 +// all the stripes and there are only 3 threads, one of the threads will
1.38 +// get the tasks with the 4th stripe. However, there is a dependence in
1.39 +// CardTableExtension::scavenge_contents_parallel() on the number
1.40 +// of tasks created. In scavenge_contents_parallel the distance
1.41 +// to the next stripe is calculated based on the number of tasks.
1.42 +// If the stripe width is ssize, a task's next stripe is at
1.43 +// ssize * number_of_tasks (= slice_stride). In this case after
1.44 +// finishing stripe 0 in slice 0, the thread finds the stripe 0 in slice1
1.45 +// by adding slice_stride to the start of stripe 0 in slice 0 to get
1.46 +// to the start of stride 0 in slice 1.
1.47
1.48 class OldToYoungRootsTask : public GCTask {
1.49 private:
1.50 PSOldGen* _gen;
1.51 HeapWord* _gen_top;
1.52 uint _stripe_number;
1.53 + uint _stripe_total;
1.54
1.55 public:
1.56 - OldToYoungRootsTask(PSOldGen *gen, HeapWord* gen_top, uint stripe_number) :
1.57 - _gen(gen), _gen_top(gen_top), _stripe_number(stripe_number) { }
1.58 + OldToYoungRootsTask(PSOldGen *gen,
1.59 + HeapWord* gen_top,
1.60 + uint stripe_number,
1.61 + uint stripe_total) :
1.62 + _gen(gen),
1.63 + _gen_top(gen_top),
1.64 + _stripe_number(stripe_number),
1.65 + _stripe_total(stripe_total) { }
1.66
1.67 char* name() { return (char *)"old-to-young-roots-task"; }
1.68
