C++ GenCollectedHeap::gen_policy方法代码示例

void ASParNewGeneration::compute_new_size() {
  GenCollectedHeap* gch = GenCollectedHeap::heap();
  assert(gch->kind() == CollectedHeap::GenCollectedHeap,
    "not a CMS generational heap");


  CMSAdaptiveSizePolicy* size_policy =
    (CMSAdaptiveSizePolicy*)gch->gen_policy()->size_policy();
  assert(size_policy->is_gc_cms_adaptive_size_policy(),
    "Wrong type of size policy");

  size_t survived = from()->used();
  if (!survivor_overflow()) {
    // Keep running averages on how much survived
    size_policy->avg_survived()->sample(survived);
  } else {
    size_t promoted =
      (size_t) next_gen()->gc_stats()->avg_promoted()->last_sample();
    assert(promoted < gch->capacity(), "Conversion problem?");
    size_t survived_guess = survived + promoted;
    size_policy->avg_survived()->sample(survived_guess);
  }

  size_t survivor_limit = max_survivor_size();
  _tenuring_threshold =
    size_policy->compute_survivor_space_size_and_threshold(
                                                     _survivor_overflow,
                                                     _tenuring_threshold,
                                                     survivor_limit);
  size_policy->avg_young_live()->sample(used());
  size_policy->avg_eden_live()->sample(eden()->used());

  size_policy->compute_young_generation_free_space(eden()->capacity(),
                                                   max_gen_size());

  resize(size_policy->calculated_eden_size_in_bytes(),
         size_policy->calculated_survivor_size_in_bytes());

  if (UsePerfData) {
    CMSGCAdaptivePolicyCounters* counters =
      (CMSGCAdaptivePolicyCounters*) gch->collector_policy()->counters();
    assert(counters->kind() ==
           GCPolicyCounters::CMSGCAdaptivePolicyCountersKind,
      "Wrong kind of counters");
    counters->update_tenuring_threshold(_tenuring_threshold);
    counters->update_survivor_overflowed(_survivor_overflow);
    counters->update_young_capacity(capacity());
  }
}

//.........这里部分代码省略.........
                                                  &fsc_with_no_gc_barrier,
                                                  &fsc_with_gc_barrier);

  assert(gch->no_allocs_since_save_marks(0),
         "save marks have not been newly set.");

  int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;

  gch->gen_process_strong_roots(_level,
                                true,  // Process younger gens, if any,
                                       // as strong roots.
                                true,  // activate StrongRootsScope
                                true,  // is scavenging
                                SharedHeap::ScanningOption(so),
                                &fsc_with_no_gc_barrier,
                                true,   // walk *all* scavengable nmethods
                                &fsc_with_gc_barrier,
                                &klass_scan_closure);

  // "evacuate followers".
  evacuate_followers.do_void();

  FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
  ReferenceProcessor* rp = ref_processor();
  rp->setup_policy(clear_all_soft_refs);
  const ReferenceProcessorStats& stats =
  rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
                                    NULL, _gc_timer);
  gc_tracer.report_gc_reference_stats(stats);

  if (!_promotion_failed) {
    // Swap the survivor spaces.
    eden()->clear(SpaceDecorator::Mangle);
    from()->clear(SpaceDecorator::Mangle);
    if (ZapUnusedHeapArea) {
      // This is now done here because of the piece-meal mangling which
      // can check for valid mangling at intermediate points in the
      // collection(s).  When a minor collection fails to collect
      // sufficient space resizing of the young generation can occur
      // an redistribute the spaces in the young generation.  Mangle
      // here so that unzapped regions don't get distributed to
      // other spaces.
      to()->mangle_unused_area();
    }
    swap_spaces();

    assert(to()->is_empty(), "to space should be empty now");

    adjust_desired_tenuring_threshold();

    // A successful scavenge should restart the GC time limit count which is
    // for full GC's.
    AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
    size_policy->reset_gc_overhead_limit_count();
    if (PrintGC && !PrintGCDetails) {
      gch->print_heap_change(gch_prev_used);
    }
    assert(!gch->incremental_collection_failed(), "Should be clear");
  } else {
    assert(_promo_failure_scan_stack.is_empty(), "post condition");
    _promo_failure_scan_stack.clear(true); // Clear cached segments.

    remove_forwarding_pointers();
    if (PrintGCDetails) {
      gclog_or_tty->print(" (promotion failed) ");
    }
    // Add to-space to the list of space to compact
    // when a promotion failure has occurred.  In that
    // case there can be live objects in to-space
    // as a result of a partial evacuation of eden
    // and from-space.
    swap_spaces();   // For uniformity wrt ParNewGeneration.
    from()->set_next_compaction_space(to());
    gch->set_incremental_collection_failed();

    // Inform the next generation that a promotion failure occurred.
    _next_gen->promotion_failure_occurred();
    gc_tracer.report_promotion_failed(_promotion_failed_info);

    // Reset the PromotionFailureALot counters.
    NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
  }
  // set new iteration safe limit for the survivor spaces
  from()->set_concurrent_iteration_safe_limit(from()->top());
  to()->set_concurrent_iteration_safe_limit(to()->top());
  SpecializationStats::print();

  // We need to use a monotonically non-decreasing time in ms
  // or we will see time-warp warnings and os::javaTimeMillis()
  // does not guarantee monotonicity.
  jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
  update_time_of_last_gc(now);

  gch->trace_heap_after_gc(&gc_tracer);
  gc_tracer.report_tenuring_threshold(tenuring_threshold());

  _gc_timer->register_gc_end();

  gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
}