Mon, 08 Dec 2014 18:57:33 +0100
8067655: Clean up G1 remembered set oop iteration
Summary: Pass on the static type G1ParPushHeapRSClosure to allow oop_iterate devirtualization
Reviewed-by: jmasa, kbarrett
1 /*
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25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP
28 #include "gc_implementation/g1/heapRegion.hpp"
29 #include "utilities/growableArray.hpp"
31 class CollectionSetChooser: public CHeapObj<mtGC> {
33 GrowableArray<HeapRegion*> _regions;
35 // Unfortunately, GrowableArray uses ints for length and indexes. To
36 // avoid excessive casting in the rest of the class the following
37 // wrapper methods are provided that use uints.
39 uint regions_length() { return (uint) _regions.length(); }
40 HeapRegion* regions_at(uint i) { return _regions.at((int) i); }
41 void regions_at_put(uint i, HeapRegion* hr) {
42 _regions.at_put((int) i, hr);
43 }
44 void regions_at_put_grow(uint i, HeapRegion* hr) {
45 _regions.at_put_grow((int) i, hr);
46 }
47 void regions_trunc_to(uint i) { _regions.trunc_to((uint) i); }
49 // The index of the next candidate old region to be considered for
50 // addition to the CSet.
51 uint _curr_index;
53 // The number of candidate old regions added to the CSet chooser.
54 // Note: this is not updated when removing a region using
55 // remove_and_move_to_next() below.
56 uint _length;
58 // Keeps track of the start of the next array chunk to be claimed by
59 // parallel GC workers.
60 uint _first_par_unreserved_idx;
62 // If a region has more live bytes than this threshold, it will not
63 // be added to the CSet chooser and will not be a candidate for
64 // collection.
65 size_t _region_live_threshold_bytes;
67 // The sum of reclaimable bytes over all the regions in the CSet chooser.
68 size_t _remaining_reclaimable_bytes;
70 public:
72 // Return the current candidate region to be considered for
73 // collection without removing it from the CSet chooser.
74 HeapRegion* peek() {
75 HeapRegion* res = NULL;
76 if (_curr_index < _length) {
77 res = regions_at(_curr_index);
78 assert(res != NULL,
79 err_msg("Unexpected NULL hr in _regions at index %u",
80 _curr_index));
81 }
82 return res;
83 }
85 // Remove the given region from the CSet chooser and move to the
86 // next one. The given region should be the current candidate region
87 // in the CSet chooser.
88 void remove_and_move_to_next(HeapRegion* hr) {
89 assert(hr != NULL, "pre-condition");
90 assert(_curr_index < _length, "pre-condition");
91 assert(regions_at(_curr_index) == hr, "pre-condition");
92 regions_at_put(_curr_index, NULL);
93 assert(hr->reclaimable_bytes() <= _remaining_reclaimable_bytes,
94 err_msg("remaining reclaimable bytes inconsistent "
95 "from region: "SIZE_FORMAT" remaining: "SIZE_FORMAT,
96 hr->reclaimable_bytes(), _remaining_reclaimable_bytes));
97 _remaining_reclaimable_bytes -= hr->reclaimable_bytes();
98 _curr_index += 1;
99 }
101 CollectionSetChooser();
103 void sort_regions();
105 // Determine whether to add the given region to the CSet chooser or
106 // not. Currently, we skip humongous regions (we never add them to
107 // the CSet, we only reclaim them during cleanup) and regions whose
108 // live bytes are over the threshold.
109 bool should_add(HeapRegion* hr) {
110 assert(hr->is_marked(), "pre-condition");
111 assert(!hr->is_young(), "should never consider young regions");
112 return !hr->isHumongous() &&
113 hr->live_bytes() < _region_live_threshold_bytes;
114 }
116 // Returns the number candidate old regions added
117 uint length() { return _length; }
119 // Serial version.
120 void add_region(HeapRegion *hr);
122 // Must be called before calls to claim_array_chunk().
123 // n_regions is the number of regions, chunk_size the chunk size.
124 void prepare_for_par_region_addition(uint n_regions, uint chunk_size);
125 // Returns the first index in a contiguous chunk of chunk_size indexes
126 // that the calling thread has reserved. These must be set by the
127 // calling thread using set_region() (to NULL if necessary).
128 uint claim_array_chunk(uint chunk_size);
129 // Set the marked array entry at index to hr. Careful to claim the index
130 // first if in parallel.
131 void set_region(uint index, HeapRegion* hr);
132 // Atomically increment the number of added regions by region_num
133 // and the amount of reclaimable bytes by reclaimable_bytes.
134 void update_totals(uint region_num, size_t reclaimable_bytes);
136 void clear();
138 // Return the number of candidate regions that remain to be collected.
139 uint remaining_regions() { return _length - _curr_index; }
141 // Determine whether the CSet chooser has more candidate regions or not.
142 bool is_empty() { return remaining_regions() == 0; }
144 // Return the reclaimable bytes that remain to be collected on
145 // all the candidate regions in the CSet chooser.
146 size_t remaining_reclaimable_bytes() { return _remaining_reclaimable_bytes; }
148 // Returns true if the used portion of "_regions" is properly
149 // sorted, otherwise asserts false.
150 void verify() PRODUCT_RETURN;
151 };
153 class CSetChooserParUpdater : public StackObj {
154 private:
155 CollectionSetChooser* _chooser;
156 bool _parallel;
157 uint _chunk_size;
158 uint _cur_chunk_idx;
159 uint _cur_chunk_end;
160 uint _regions_added;
161 size_t _reclaimable_bytes_added;
163 public:
164 CSetChooserParUpdater(CollectionSetChooser* chooser,
165 bool parallel, uint chunk_size) :
166 _chooser(chooser), _parallel(parallel), _chunk_size(chunk_size),
167 _cur_chunk_idx(0), _cur_chunk_end(0),
168 _regions_added(0), _reclaimable_bytes_added(0) { }
170 ~CSetChooserParUpdater() {
171 if (_parallel && _regions_added > 0) {
172 _chooser->update_totals(_regions_added, _reclaimable_bytes_added);
173 }
174 }
176 void add_region(HeapRegion* hr) {
177 if (_parallel) {
178 if (_cur_chunk_idx == _cur_chunk_end) {
179 _cur_chunk_idx = _chooser->claim_array_chunk(_chunk_size);
180 _cur_chunk_end = _cur_chunk_idx + _chunk_size;
181 }
182 assert(_cur_chunk_idx < _cur_chunk_end, "invariant");
183 _chooser->set_region(_cur_chunk_idx, hr);
184 _cur_chunk_idx += 1;
185 } else {
186 _chooser->add_region(hr);
187 }
188 _regions_added += 1;
189 _reclaimable_bytes_added += hr->reclaimable_bytes();
190 }
192 bool should_add(HeapRegion* hr) { return _chooser->should_add(hr); }
193 };
195 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP