src/hotspot/share/gc/g1/g1FullCollector.cpp

@@ -38,10 +38,11 @@
  #include "gc/g1/g1RegionMarkStatsCache.inline.hpp"
  #include "gc/shared/gcTraceTime.inline.hpp"
  #include "gc/shared/preservedMarks.inline.hpp"
  #include "gc/shared/classUnloadingContext.hpp"
  #include "gc/shared/referenceProcessor.hpp"
+ #include "gc/shared/slidingForwarding.hpp"
  #include "gc/shared/verifyOption.hpp"
  #include "gc/shared/weakProcessor.inline.hpp"
  #include "gc/shared/workerPolicy.hpp"
  #include "logging/log.hpp"
  #include "runtime/handles.inline.hpp"

@@ -207,10 +208,12 @@
    verify_after_marking();
  
    // Don't add any more derived pointers during later phases
    deactivate_derived_pointers();
  
+   SlidingForwarding::begin();
+ 
    phase2_prepare_compaction();
  
    if (has_compaction_targets()) {
      phase3_adjust_pointers();
  

@@ -219,10 +222,12 @@
      // All regions have a high live ratio thus will not be compacted.
      // The live ratio is only considered if do_maximal_compaction is false.
      log_info(gc, phases) ("No Regions selected for compaction. Skipping Phase 3: Adjust pointers and Phase 4: Compact heap");
    }
  
+   SlidingForwarding::end();
+ 
    phase5_reset_metadata();
  
    G1CollectedHeap::finish_codecache_marking_cycle();
  }
  

@@ -387,11 +392,12 @@
      }
    }
    return lowest_current;
  }
  
- void G1FullCollector::phase2c_prepare_serial_compaction() {
+ template <bool ALT_FWD>
+ void G1FullCollector::phase2c_prepare_serial_compaction_impl() {
    GCTraceTime(Debug, gc, phases) debug("Phase 2: Prepare serial compaction", scope()->timer());
    // At this point, we know that after parallel compaction there will be regions that
    // are partially compacted into. Thus, the last compaction region of all
    // compaction queues still have space in them. We try to re-compact these regions
    // in serial to avoid a premature OOM when the mutator wants to allocate the first

@@ -412,11 +418,11 @@
    HeapRegion* start_hr = _heap->region_at(start_serial);
    serial_cp->add(start_hr);
    serial_cp->initialize(start_hr);
  
    HeapWord* dense_prefix_top = compaction_top(start_hr);
-   G1SerialRePrepareClosure re_prepare(serial_cp, dense_prefix_top);
+   G1SerialRePrepareClosure<ALT_FWD> re_prepare(serial_cp, dense_prefix_top);
  
    for (uint i = start_serial + 1; i < _heap->max_reserved_regions(); i++) {
      if (is_compaction_target(i)) {
        HeapRegion* current = _heap->region_at(i);
        set_compaction_top(current, current->bottom());

@@ -425,11 +431,20 @@
      }
    }
    serial_cp->update();
  }
  
- void G1FullCollector::phase2d_prepare_humongous_compaction() {
+ void G1FullCollector::phase2c_prepare_serial_compaction() {
+   if (UseAltGCForwarding) {
+     phase2c_prepare_serial_compaction_impl<true>();
+   } else {
+     phase2c_prepare_serial_compaction_impl<false>();
+   }
+ }
+ 
+ template <bool ALT_FWD>
+ void G1FullCollector::phase2d_prepare_humongous_compaction_impl() {
    GCTraceTime(Debug, gc, phases) debug("Phase 2: Prepare humongous compaction", scope()->timer());
    G1FullGCCompactionPoint* serial_cp = serial_compaction_point();
    assert(serial_cp->has_regions(), "Sanity!" );
  
    uint last_serial_target = serial_cp->current_region()->hrm_index();

@@ -443,21 +458,29 @@
  
      if (hr == nullptr) {
        region_index++;
        continue;
      } else if (hr->is_starts_humongous()) {
-       uint num_regions = humongous_cp->forward_humongous(hr);
+       uint num_regions = humongous_cp->forward_humongous<ALT_FWD>(hr);
        region_index += num_regions; // Skip over the continues humongous regions.
        continue;
      } else if (is_compaction_target(region_index)) {
        // Add the region to the humongous compaction point.
        humongous_cp->add(hr);
      }
      region_index++;
    }
  }
  
+ void G1FullCollector::phase2d_prepare_humongous_compaction() {
+   if (UseAltGCForwarding) {
+     phase2d_prepare_humongous_compaction_impl<true>();
+   } else {
+     phase2d_prepare_humongous_compaction_impl<false>();
+   }
+ }
+ 
  void G1FullCollector::phase3_adjust_pointers() {
    // Adjust the pointers to reflect the new locations
    GCTraceTime(Info, gc, phases) info("Phase 3: Adjust pointers", scope()->timer());
  
    G1FullGCAdjustTask task(this);