changeset 11278:16098172056c

8153117: Back out JDK-8142935 until JDK-8152723 fixed Summary: JDK-8142935 fix can lead to avoidable Full GCs Reviewed-by: jwilhelm, tschatzl Contributed-by: tom.benson@oracle.com
author tbenson
date Tue, 05 Apr 2016 11:17:50 -0400
parents aff43ebb503f
children 691c69fa726c bf308b2affed
files src/share/vm/gc/g1/g1CollectionSet.cpp src/share/vm/gc/g1/g1CollectionSet.hpp src/share/vm/gc/g1/g1CollectorPolicy.cpp src/share/vm/gc/g1/g1CollectorPolicy.hpp
diffstat 4 files changed, 6 insertions(+), 50 deletions(-) [+]
line wrap: on
line diff
--- a/src/share/vm/gc/g1/g1CollectionSet.cpp	Tue Apr 05 09:42:27 2016 -0400
+++ b/src/share/vm/gc/g1/g1CollectionSet.cpp	Tue Apr 05 11:17:50 2016 -0400
@@ -59,14 +59,12 @@
 
   _head(NULL),
   _bytes_used_before(0),
-  _bytes_live_before(0),
   _recorded_rs_lengths(0),
   // Incremental CSet attributes
   _inc_build_state(Inactive),
   _inc_head(NULL),
   _inc_tail(NULL),
   _inc_bytes_used_before(0),
-  _inc_bytes_live_before(0),
   _inc_recorded_rs_lengths(0),
   _inc_recorded_rs_lengths_diffs(0),
   _inc_predicted_elapsed_time_ms(0.0),
@@ -97,7 +95,6 @@
   hr->set_next_in_collection_set(_head);
   _head = hr;
   _bytes_used_before += hr->used();
-  _bytes_live_before += hr->live_bytes();
   size_t rs_length = hr->rem_set()->occupied();
   _recorded_rs_lengths += rs_length;
   _old_region_length += 1;
@@ -110,7 +107,6 @@
   _inc_head = NULL;
   _inc_tail = NULL;
   _inc_bytes_used_before = 0;
-  _inc_bytes_live_before = 0;
 
   _inc_recorded_rs_lengths = 0;
   _inc_recorded_rs_lengths_diffs = 0;
@@ -213,7 +209,6 @@
   _inc_recorded_rs_lengths += rs_length;
   _inc_predicted_elapsed_time_ms += region_elapsed_time_ms;
   _inc_bytes_used_before += used_bytes;
-  _inc_bytes_live_before += hr->live_bytes();
 
   assert(!hr->in_collection_set(), "invariant");
   _g1->register_young_region_with_cset(hr);
@@ -316,7 +311,6 @@
 
   _head = _inc_head;
   _bytes_used_before = _inc_bytes_used_before;
-  _bytes_live_before = _inc_bytes_live_before;
   time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0);
 
   log_trace(gc, ergo, cset)("Add young regions to CSet. eden: %u regions, survivors: %u regions, predicted young region time: %1.2fms, target pause time: %1.2fms",
@@ -340,7 +334,6 @@
     cset_chooser()->verify();
     const uint min_old_cset_length = _policy->calc_min_old_cset_length();
     const uint max_old_cset_length = _policy->calc_max_old_cset_length();
-    const size_t estimated_available_bytes = _policy->available_bytes_estimate();
 
     uint expensive_region_num = 0;
     bool check_time_remaining = _policy->adaptive_young_list_length();
@@ -369,13 +362,6 @@
         break;
       }
 
-      // Stop adding regions if the live bytes (according to the last marking)
-      // added so far would exceed the estimated free bytes.
-      if ((_bytes_live_before + hr->live_bytes()) > estimated_available_bytes) {
-        log_debug(gc, ergo, cset)("Finish adding old regions to CSet (reached estimated free space limit)");
-        break;
-      }
-
       double predicted_time_ms = predict_region_elapsed_time_ms(hr);
       if (check_time_remaining) {
         if (predicted_time_ms > time_remaining_ms) {
--- a/src/share/vm/gc/g1/g1CollectionSet.hpp	Tue Apr 05 09:42:27 2016 -0400
+++ b/src/share/vm/gc/g1/g1CollectionSet.hpp	Tue Apr 05 11:17:50 2016 -0400
@@ -57,9 +57,6 @@
   // (if any) to the collection set.
   size_t _bytes_used_before;
 
-  // The sum of live bytes in the collection set, set as described above.
-  size_t _bytes_live_before;
-
   size_t _recorded_rs_lengths;
 
   // The associated information that is maintained while the incremental
@@ -84,9 +81,6 @@
   // an evacuation pause.
   size_t _inc_bytes_used_before;
 
-  // The number of live bytes in the incrementally built collection set.
-  size_t _inc_bytes_live_before;
-
   // The RSet lengths recorded for regions in the CSet. It is updated
   // by the thread that adds a new region to the CSet. We assume that
   // only one thread can be allocating a new CSet region (currently,
@@ -179,10 +173,6 @@
     _bytes_used_before = 0;
   }
 
-  void reset_bytes_live_before() {
-    _bytes_live_before = 0;
-  }
-
   // Choose a new collection set.  Marks the chosen regions as being
   // "in_collection_set", and links them together.  The head and number of
   // the collection set are available via access methods.
--- a/src/share/vm/gc/g1/g1CollectorPolicy.cpp	Tue Apr 05 09:42:27 2016 -0400
+++ b/src/share/vm/gc/g1/g1CollectorPolicy.cpp	Tue Apr 05 11:17:50 2016 -0400
@@ -221,7 +221,12 @@
   // When copying, we will likely need more bytes free than is live in the region.
   // Add some safety margin to factor in the confidence of our guess, and the
   // natural expected waste.
-  size_t expected_bytes_to_copy = (size_t)(bytes_to_copy * safety_factor());
+  // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
+  // of the calculation: the lower the confidence, the more headroom.
+  // (100 + TargetPLABWastePct) represents the increase in expected bytes during
+  // copying due to anticipated waste in the PLABs.
+  double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
+  size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
 
   if (expected_bytes_to_copy > free_bytes) {
     // end condition 3: out-of-space
@@ -587,7 +592,6 @@
   _pending_cards = _g1->pending_card_num();
 
   _collection_set->reset_bytes_used_before();
-  _collection_set->reset_bytes_live_before();
   _bytes_copied_during_gc = 0;
 
   collector_state()->set_last_gc_was_young(false);
@@ -1262,15 +1266,6 @@
   return (uint) result;
 }
 
-size_t G1CollectorPolicy::available_bytes_estimate() {
-  size_t estimated_available_bytes = 0;
-  if (_free_regions_at_end_of_collection > _reserve_regions) {
-    uint available_regions = _free_regions_at_end_of_collection - _reserve_regions;
-    estimated_available_bytes = (size_t)((available_regions * HeapRegion::GrainBytes) / safety_factor());
-  }
-  return estimated_available_bytes;
-}
-
 void G1CollectorPolicy::finalize_collection_set(double target_pause_time_ms) {
   double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms);
   _collection_set->finalize_old_part(time_remaining_ms);
--- a/src/share/vm/gc/g1/g1CollectorPolicy.hpp	Tue Apr 05 09:42:27 2016 -0400
+++ b/src/share/vm/gc/g1/g1CollectorPolicy.hpp	Tue Apr 05 11:17:50 2016 -0400
@@ -169,21 +169,6 @@
 
   double accum_yg_surv_rate_pred(int age) const;
 
-  // When copying, we will likely need more bytes free than is live in the region.
-  // Add some safety margin to factor in the confidence of our guess, and the
-  // natural expected waste.
-  // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
-  // of the calculation: the lower the confidence, the more headroom.
-  // (100 + TargetPLABWastePct) represents the increase in expected bytes during
-  // copying due to anticipated waste in the PLABs.
-  double safety_factor() const {
-    return (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
-  }
-
-  // Returns an estimate of the available bytes at end of collection, adjusted by
-  // the safety factor.
-  size_t available_bytes_estimate();
-
 protected:
   G1CollectionSet* _collection_set;
   virtual double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;