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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.

  *

  * 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.

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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"

 class CollectionSetChooser: public CHeapObj<mtGC> {

   GrowableArray<HeapRegion*> _regions;

   // Unfortunately, GrowableArray uses ints for length and indexes. To

   // avoid excessive casting in the rest of the class the following

   // wrapper methods are provided that use uints.

   uint regions_length()          { return (uint) _regions.length(); }

   HeapRegion* regions_at(uint i) { return _regions.at((int) i);     }

   void regions_at_put(uint i, HeapRegion* hr) {

     _regions.at_put((int) i, hr);

   }

   void regions_at_put_grow(uint i, HeapRegion* hr) {

     _regions.at_put_grow((int) i, hr);

   }

   void regions_trunc_to(uint i)  { _regions.trunc_to((uint) i); }

   // The index of the next candidate old region to be considered for

   // addition to the CSet.

   uint _curr_index;

   // The number of candidate old regions added to the CSet chooser.

   // Note: this is not updated when removing a region using

   // remove_and_move_to_next() below.

   uint _length;

   // Keeps track of the start of the next array chunk to be claimed by

   // parallel GC workers.

   uint _first_par_unreserved_idx;

   // If a region has more live bytes than this threshold, it will not

   // be added to the CSet chooser and will not be a candidate for

   // collection.

   size_t _region_live_threshold_bytes;

   // The sum of reclaimable bytes over all the regions in the CSet chooser.

   size_t _remaining_reclaimable_bytes;

 public:

   // Return the current candidate region to be considered for

   // collection without removing it from the CSet chooser.

   HeapRegion* peek() {

     HeapRegion* res = NULL;

     if (_curr_index < _length) {

       res = regions_at(_curr_index);

       assert(res != NULL,

              err_msg("Unexpected NULL hr in _regions at index %u",

                      _curr_index));

     }

     return res;

   }

   // Remove the given region from the CSet chooser and move to the

   // next one. The given region should be the current candidate region

   // in the CSet chooser.

   void remove_and_move_to_next(HeapRegion* hr) {

     assert(hr != NULL, "pre-condition");

     assert(_curr_index < _length, "pre-condition");

     assert(regions_at(_curr_index) == hr, "pre-condition");

     regions_at_put(_curr_index, NULL);

     assert(hr->reclaimable_bytes() <= _remaining_reclaimable_bytes,

            err_msg("remaining reclaimable bytes inconsistent "

                    "from region: "SIZE_FORMAT" remaining: "SIZE_FORMAT,

                    hr->reclaimable_bytes(), _remaining_reclaimable_bytes));

     _remaining_reclaimable_bytes -= hr->reclaimable_bytes();

     _curr_index += 1;

   }

   CollectionSetChooser();

   void sort_regions();

   // Determine whether to add the given region to the CSet chooser or

   // not. Currently, we skip humongous regions (we never add them to

   // the CSet, we only reclaim them during cleanup) and regions whose

   // live bytes are over the threshold.

   bool should_add(HeapRegion* hr) {

     assert(hr->is_marked(), "pre-condition");

     assert(!hr->is_young(), "should never consider young regions");

     return !hr->isHumongous() &&

             hr->live_bytes() < _region_live_threshold_bytes;

   }

   // Returns the number candidate old regions added

   uint length() { return _length; }

   // Serial version.

   void add_region(HeapRegion *hr);

   // Must be called before calls to claim_array_chunk().

   // n_regions is the number of regions, chunk_size the chunk size.

   void prepare_for_par_region_addition(uint n_regions, uint chunk_size);

   // Returns the first index in a contiguous chunk of chunk_size indexes

   // that the calling thread has reserved.  These must be set by the

   // calling thread using set_region() (to NULL if necessary).

   uint claim_array_chunk(uint chunk_size);

   // Set the marked array entry at index to hr.  Careful to claim the index

   // first if in parallel.

   void set_region(uint index, HeapRegion* hr);

   // Atomically increment the number of added regions by region_num

   // and the amount of reclaimable bytes by reclaimable_bytes.

   void update_totals(uint region_num, size_t reclaimable_bytes);

   void clear();

   // Return the number of candidate regions that remain to be collected.

   uint remaining_regions() { return _length - _curr_index; }

   // Determine whether the CSet chooser has more candidate regions or not.

   bool is_empty() { return remaining_regions() == 0; }

   // Return the reclaimable bytes that remain to be collected on

   // all the candidate regions in the CSet chooser.

   size_t remaining_reclaimable_bytes() { return _remaining_reclaimable_bytes; }

   // Returns true if the used portion of "_regions" is properly

   // sorted, otherwise asserts false.

   void verify() PRODUCT_RETURN;

 };

 class CSetChooserParUpdater : public StackObj {

 private:

   CollectionSetChooser* _chooser;

   bool _parallel;

   uint _chunk_size;

   uint _cur_chunk_idx;

   uint _cur_chunk_end;

   uint _regions_added;

   size_t _reclaimable_bytes_added;

 public:

   CSetChooserParUpdater(CollectionSetChooser* chooser,

                         bool parallel, uint chunk_size) :

     _chooser(chooser), _parallel(parallel), _chunk_size(chunk_size),

     _cur_chunk_idx(0), _cur_chunk_end(0),

     _regions_added(0), _reclaimable_bytes_added(0) { }

   ~CSetChooserParUpdater() {

     if (_parallel && _regions_added > 0) {

       _chooser->update_totals(_regions_added, _reclaimable_bytes_added);

     }

   }

   void add_region(HeapRegion* hr) {

     if (_parallel) {

       if (_cur_chunk_idx == _cur_chunk_end) {

         _cur_chunk_idx = _chooser->claim_array_chunk(_chunk_size);

         _cur_chunk_end = _cur_chunk_idx + _chunk_size;

       }

       assert(_cur_chunk_idx < _cur_chunk_end, "invariant");

       _chooser->set_region(_cur_chunk_idx, hr);

       _cur_chunk_idx += 1;

     } else {

       _chooser->add_region(hr);

     }

     _regions_added += 1;

     _reclaimable_bytes_added += hr->reclaimable_bytes();

   }

   bool should_add(HeapRegion* hr) { return _chooser->should_add(hr); }

 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP