diff src/share/vm/gc_implementation/g1/g1RemSet.cpp @ 20504:6948da6d7c13

8052172: Evacuation failure handling in G1 does not evacuate all objects if -XX:-G1DeferredRSUpdate is set Summary: Remove -XX:-G1DeferredRSUpdate functionality as it is racy. During evacuation failure handling, threads where evacuation failure handling occurred may try to add remembered sets to regions which remembered sets are currently being scanned. The iterator to handle the remembered set scan does not support addition of entries during scan and so may skip valid references. Reviewed-by: iveresov, brutisso, mgerdin
author tschatzl
date Tue, 30 Sep 2014 09:44:36 +0200
parents 7baf47cb97cb
children 7848fc12602b 80ac3ee51955 b554c7fa9478
line wrap: on
line diff
--- a/src/share/vm/gc_implementation/g1/g1RemSet.cpp	Wed Sep 10 11:55:33 2014 +0200
+++ b/src/share/vm/gc_implementation/g1/g1RemSet.cpp	Tue Sep 30 09:44:36 2014 +0200
@@ -338,12 +338,8 @@
   // are just discarded (there's no need to update the RSets of regions
   // that were in the collection set - after the pause these regions
   // are wholly 'free' of live objects. In the event of an evacuation
-  // failure the cards/buffers in this queue set are:
-  // * passed to the DirtyCardQueueSet that is used to manage deferred
-  //   RSet updates, or
-  // * scanned for references that point into the collection set
-  //   and the RSet of the corresponding region in the collection set
-  //   is updated immediately.
+  // failure the cards/buffers in this queue set are passed to the
+  // DirtyCardQueueSet that is used to manage RSet updates
   DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());
 
   assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");
@@ -372,7 +368,6 @@
 
 void G1RemSet::prepare_for_oops_into_collection_set_do() {
   cleanupHRRS();
-  ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();
   _g1->set_refine_cte_cl_concurrency(false);
   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
   dcqs.concatenate_logs();
@@ -385,66 +380,6 @@
   _total_cards_scanned = 0;
 }
 
-
-// This closure, applied to a DirtyCardQueueSet, is used to immediately
-// update the RSets for the regions in the CSet. For each card it iterates
-// through the oops which coincide with that card. It scans the reference
-// fields in each oop; when it finds an oop that points into the collection
-// set, the RSet for the region containing the referenced object is updated.
-class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {
-  G1CollectedHeap* _g1;
-  CardTableModRefBS* _ct_bs;
-public:
-  UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,
-                                          CardTableModRefBS* bs):
-    _g1(g1), _ct_bs(bs)
-  { }
-
-  bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
-    // Construct the region representing the card.
-    HeapWord* start = _ct_bs->addr_for(card_ptr);
-    // And find the region containing it.
-    HeapRegion* r = _g1->heap_region_containing(start);
-
-    // Scan oops in the card looking for references into the collection set
-    // Don't use addr_for(card_ptr + 1) which can ask for
-    // a card beyond the heap.  This is not safe without a perm
-    // gen.
-    HeapWord* end   = start + CardTableModRefBS::card_size_in_words;
-    MemRegion scanRegion(start, end);
-
-    UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());
-    FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);
-    FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);
-
-    // We can pass false as the "filter_young" parameter here as:
-    // * we should be in a STW pause,
-    // * the DCQS to which this closure is applied is used to hold
-    //   references that point into the collection set from the prior
-    //   RSet updating,
-    // * the post-write barrier shouldn't be logging updates to young
-    //   regions (but there is a situation where this can happen - see
-    //   the comment in G1RemSet::refine_card() below -
-    //   that should not be applicable here), and
-    // * during actual RSet updating, the filtering of cards in young
-    //   regions in HeapRegion::oops_on_card_seq_iterate_careful is
-    //   employed.
-    // As a result, when this closure is applied to "refs into cset"
-    // DCQS, we shouldn't see any cards in young regions.
-    update_rs_cl.set_region(r);
-    HeapWord* stop_point =
-      r->oops_on_card_seq_iterate_careful(scanRegion,
-                                          &filter_then_update_rs_cset_oop_cl,
-                                          false /* filter_young */,
-                                          NULL  /* card_ptr */);
-
-    // Since this is performed in the event of an evacuation failure, we
-    // we shouldn't see a non-null stop point
-    assert(stop_point == NULL, "saw an unallocated region");
-    return true;
-  }
-};
-
 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
   guarantee( _cards_scanned != NULL, "invariant" );
   _total_cards_scanned = 0;
@@ -465,25 +400,10 @@
     double restore_remembered_set_start = os::elapsedTime();
 
     // Restore remembered sets for the regions pointing into the collection set.
-    if (G1DeferredRSUpdate) {
-      // If deferred RS updates are enabled then we just need to transfer
-      // the completed buffers from (a) the DirtyCardQueueSet used to hold
-      // cards that contain references that point into the collection set
-      // to (b) the DCQS used to hold the deferred RS updates
-      _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
-    } else {
-
-      CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set();
-      UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs);
-
-      int n_completed_buffers = 0;
-      while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate,
-                                                    0, 0, true)) {
-        n_completed_buffers++;
-      }
-      assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers");
-    }
-
+    // We just need to transfer the completed buffers from the DirtyCardQueueSet
+    // used to hold cards that contain references that point into the collection set
+    // to the DCQS used to hold the deferred RS updates.
+    _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
     _g1->g1_policy()->phase_times()->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0);
   }