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diff src/share/vm/gc_implementation/g1/heapRegion.cpp @ 3979:4dfb2df418f2

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6484982: G1: process references during evacuation pauses Summary: G1 now uses two reference processors - one is used by concurrent marking and the other is used by STW GCs (both full and incremental evacuation pauses). In an evacuation pause, the reference processor is embedded into the closures used to scan objects. Doing so causes causes reference objects to be 'discovered' by the reference processor. At the end of the evacuation pause, these discovered reference objects are processed - preserving (and copying) referent objects (and their reachable graphs) as appropriate. Reviewed-by: ysr, jwilhelm, brutisso, stefank, tonyp
author johnc
date Thu, 22 Sep 2011 10:57:37 -0700
parents f0ecbe78fc7b
children 811ec3d0833b
line wrap: on
line diff
--- a/src/share/vm/gc_implementation/g1/heapRegion.cpp	Thu Sep 22 07:18:51 2011 -0400
+++ b/src/share/vm/gc_implementation/g1/heapRegion.cpp	Thu Sep 22 10:57:37 2011 -0700
@@ -45,7 +45,7 @@
                                  FilterKind fk) :
   ContiguousSpaceDCTOC(hr, cl, precision, NULL),
   _hr(hr), _fk(fk), _g1(g1)
-{}
+{ }
 
 FilterOutOfRegionClosure::FilterOutOfRegionClosure(HeapRegion* r,
                                                    OopClosure* oc) :
@@ -214,8 +214,37 @@
   int oop_size;
 
   OopClosure* cl2 = cl;
-  FilterIntoCSClosure intoCSFilt(this, g1h, cl);
+
+  // If we are scanning the remembered sets looking for refs
+  // into the collection set during an evacuation pause then
+  // we will want to 'discover' reference objects that point
+  // to referents in the collection set.
+  //
+  // Unfortunately it is an instance of FilterIntoCSClosure
+  // that is iterated over the reference fields of oops in
+  // mr (and not the G1ParPushHeapRSClosure - which is the
+  // cl parameter).
+  // If we set the _ref_processor field in the FilterIntoCSClosure
+  // instance, all the reference objects that are walked
+  // (regardless of whether their referent object's are in
+  // the cset) will be 'discovered'.
+  //
+  // The G1STWIsAlive closure considers a referent object that
+  // is outside the cset as alive. The G1CopyingKeepAliveClosure
+  // skips referents that are not in the cset.
+  //
+  // Therefore reference objects in mr with a referent that is
+  // outside the cset should be OK.
+
+  ReferenceProcessor* rp = _cl->_ref_processor;
+  if (rp != NULL) {
+    assert(rp == _g1->ref_processor_stw(), "should be stw");
+    assert(_fk == IntoCSFilterKind, "should be looking for refs into CS");
+  }
+
+  FilterIntoCSClosure intoCSFilt(this, g1h, cl, rp);
   FilterOutOfRegionClosure outOfRegionFilt(_hr, cl);
+
   switch (_fk) {
   case IntoCSFilterKind:      cl2 = &intoCSFilt; break;
   case OutOfRegionFilterKind: cl2 = &outOfRegionFilt; break;
@@ -239,16 +268,19 @@
     case NoFilterKind:
       bottom = walk_mem_region_loop(cl, g1h, _hr, bottom, top);
       break;
+
     case IntoCSFilterKind: {
-      FilterIntoCSClosure filt(this, g1h, cl);
+      FilterIntoCSClosure filt(this, g1h, cl, rp);
       bottom = walk_mem_region_loop(&filt, g1h, _hr, bottom, top);
       break;
     }
+
     case OutOfRegionFilterKind: {
       FilterOutOfRegionClosure filt(_hr, cl);
       bottom = walk_mem_region_loop(&filt, g1h, _hr, bottom, top);
       break;
     }
+
     default:
       ShouldNotReachHere();
     }
@@ -483,7 +515,7 @@
 HeapRegion(size_t hrs_index, G1BlockOffsetSharedArray* sharedOffsetArray,
            MemRegion mr, bool is_zeroed)
   : G1OffsetTableContigSpace(sharedOffsetArray, mr, is_zeroed),
-    _next_fk(HeapRegionDCTOC::NoFilterKind), _hrs_index(hrs_index),
+    _hrs_index(hrs_index),
     _humongous_type(NotHumongous), _humongous_start_region(NULL),
     _in_collection_set(false),
     _next_in_special_set(NULL), _orig_end(NULL),