view src/share/vm/gc_implementation/g1/collectionSetChooser.hpp @ 2034:7e37af9d69ef

7011379: G1: overly long concurrent marking cycles Summary: This changeset introduces filtering of SATB buffers at the point when they are about to be enqueued. If this filtering clears enough entries on each buffer, the buffer can then be re-used and not enqueued. This cuts down the number of SATB buffers that need to be processed by the concurrent marking threads. Reviewed-by: johnc, ysr
author tonyp
date Wed, 19 Jan 2011 09:35:17 -0500
parents c18cbe5936b8
children 371bbc844bf1
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit if you need additional information or have any
 * questions.


#include "gc_implementation/g1/heapRegion.hpp"
#include "utilities/growableArray.hpp"

// We need to sort heap regions by collection desirability.

class CSetChooserCache VALUE_OBJ_CLASS_SPEC {
  enum {
    CacheLength = 16
  } PrivateConstants;

  HeapRegion*  _cache[CacheLength];
  int          _occupancy; // number of region in cache
  int          _first; // "first" region in the cache

  // adding CacheLength to deal with negative values
  inline int trim_index(int index) {
    return (index + CacheLength) % CacheLength;

  inline int get_sort_index(int index) {
    return -index-2;
  inline int get_index(int sort_index) {
    return -sort_index-2;


  inline int occupancy(void) { return _occupancy; }
  inline bool is_full()      { return _occupancy == CacheLength; }
  inline bool is_empty()     { return _occupancy == 0; }

  void clear(void);
  void insert(HeapRegion *hr);
  HeapRegion *remove_first(void);
  void remove (HeapRegion *hr);
  inline HeapRegion *get_first(void) {
    return _cache[_first];

#ifndef PRODUCT
  bool verify (void);
  bool region_in_cache(HeapRegion *hr) {
    int sort_index = hr->sort_index();
    if (sort_index < -1) {
      int index = get_index(sort_index);
      guarantee(index < CacheLength, "should be within bounds");
      return _cache[index] == hr;
    } else
      return 0;
#endif // PRODUCT

class CollectionSetChooser: public CHeapObj {

  GrowableArray<HeapRegion*> _markedRegions;
  int _curMarkedIndex;
  int _numMarkedRegions;
  CSetChooserCache _cache;

  // True iff last collection pause ran of out new "age 0" regions, and
  // returned an "age 1" region.
  bool _unmarked_age_1_returned_as_new;

  jint _first_par_unreserved_idx;


  HeapRegion* getNextMarkedRegion(double time_so_far, double avg_prediction);


  void printSortedHeapRegions();

  void sortMarkedHeapRegions();
  void fillCache();
  bool addRegionToCache(void);
  void addMarkedHeapRegion(HeapRegion *hr);

  // Must be called before calls to getParMarkedHeapRegionChunk.
  // "n_regions" is the number of regions, "chunkSize" the chunk size.
  void prepareForAddMarkedHeapRegionsPar(size_t n_regions, size_t chunkSize);
  // Returns the first index in a contiguous chunk of "n_regions" indexes
  // that the calling thread has reserved.  These must be set by the
  // calling thread using "setMarkedHeapRegion" (to NULL if necessary).
  jint getParMarkedHeapRegionChunk(jint n_regions);
  // Set the marked array entry at index to hr.  Careful to claim the index
  // first if in parallel.
  void setMarkedHeapRegion(jint index, HeapRegion* hr);
  // Atomically increment the number of claimed regions by "inc_by".
  void incNumMarkedHeapRegions(jint inc_by);

  void clearMarkedHeapRegions();

  void updateAfterFullCollection();

  // Ensure that "hr" is not a member of the marked region array or the cache
  void removeRegion(HeapRegion* hr);

  bool unmarked_age_1_returned_as_new() { return _unmarked_age_1_returned_as_new; }

  // Returns true if the used portion of "_markedRegions" is properly
  // sorted, otherwise asserts false.
#ifndef PRODUCT
  bool verify(void);
  bool regionProperlyOrdered(HeapRegion* r) {
    int si = r->sort_index();
    return (si == -1) ||
      (si > -1 && == r) ||
      (si < -1 && _cache.region_in_cache(r));