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 /*

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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  * This code is free software; you can redistribute it and/or modify it

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  * published by the Free Software Foundation.

  *

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  * 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.

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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP

 #include "gc_implementation/g1/heapRegion.hpp"

 #include "utilities/growableArray.hpp"

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

 // This sorting is currently done in two "stages". An initial sort is

 // done following a cleanup pause as soon as all of the marked but

 // non-empty regions have been identified and the completely empty

 // ones reclaimed.

 // This gives us a global sort on a GC efficiency metric

 // based on predictive data available at that time. However,

 // any of these regions that are collected will only be collected

 // during a future GC pause, by which time it is possible that newer

 // data might allow us to revise and/or refine the earlier

 // pause predictions, leading to changes in expected gc efficiency

 // order. To somewhat mitigate this obsolescence, more so in the

 // case of regions towards the end of the list, which will be

 // picked later, these pre-sorted regions from the _markedRegions

 // array are not used as is, but a small prefix thereof is

 // insertion-sorted again into a small cache, based on more

 // recent remembered set information. Regions are then drawn

 // from this cache to construct the collection set at each

 // incremental GC.

 // This scheme and/or its implementation may be subject to

 // revision in the future.

 class CSetChooserCache VALUE_OBJ_CLASS_SPEC {

 private:

   enum {

     CacheLength = 16

   } PrivateConstants;

   HeapRegion*  _cache[CacheLength];

   int          _occupancy; // number of regions in cache

   int          _first;     // (index of) "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;

   }

 public:

   CSetChooserCache(void);

   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);

   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;

 public:

   HeapRegion* getNextMarkedRegion(double time_so_far, double avg_prediction);

   CollectionSetChooser();

   void sortMarkedHeapRegions();

   void fillCache();

   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();

   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 && _markedRegions.at(si) == r) ||

       (si < -1 && _cache.region_in_cache(r));

   }

 #endif

 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP