9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_GC_G1_COLLECTIONSETCHOOSER_HPP
26 #define SHARE_GC_G1_COLLECTIONSETCHOOSER_HPP
27
28 #include "gc/g1/heapRegion.hpp"
29 #include "utilities/growableArray.hpp"
30
31 class CollectionSetChooser: public CHeapObj<mtGC> {
32
33 GrowableArray<HeapRegion*> _regions;
34
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.
38
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); }
48
49 // The index of the next candidate old region to be considered for
50 // addition to the CSet.
51 uint _front;
52
53 // The index of the last candidate old region
54 uint _end;
55
56 // Keeps track of the start of the next array chunk to be claimed by
57 // parallel GC workers.
58 uint _first_par_unreserved_idx;
59
60 // If a region has more live bytes than this threshold, it will not
61 // be added to the CSet chooser and will not be a candidate for
62 // collection.
63 size_t _region_live_threshold_bytes;
64
65 // The sum of reclaimable bytes over all the regions in the CSet chooser.
66 size_t _remaining_reclaimable_bytes;
67
68 // Calculate and return chunk size (in number of regions) for parallel
69 // addition of regions
70 uint calculate_parallel_work_chunk_size(uint n_workers, uint n_regions) const;
71 public:
72
73 // Return the current candidate region to be considered for
74 // collection without removing it from the CSet chooser.
75 HeapRegion* peek() {
76 HeapRegion* res = NULL;
77 if (_front < _end) {
78 res = regions_at(_front);
79 assert(res != NULL, "Unexpected NULL hr in _regions at index %u", _front);
80 }
81 return res;
82 }
83
84 // Remove the given region from the CSet chooser and move to the
85 // next one.
86 HeapRegion* pop() {
87 HeapRegion* hr = regions_at(_front);
88 assert(hr != NULL, "pre-condition");
89 assert(_front < _end, "pre-condition");
90 regions_at_put(_front, NULL);
91 assert(hr->reclaimable_bytes() <= _remaining_reclaimable_bytes,
92 "remaining reclaimable bytes inconsistent "
93 "from region: " SIZE_FORMAT " remaining: " SIZE_FORMAT,
94 hr->reclaimable_bytes(), _remaining_reclaimable_bytes);
95 _remaining_reclaimable_bytes -= hr->reclaimable_bytes();
96 _front += 1;
97 return hr;
98 }
99
100 void push(HeapRegion* hr);
101
102 CollectionSetChooser();
103
104 static size_t mixed_gc_live_threshold_bytes() {
105 return HeapRegion::GrainBytes * (size_t) G1MixedGCLiveThresholdPercent / 100;
106 }
107
108 static bool region_occupancy_low_enough_for_evac(size_t live_bytes);
109
110 void sort_regions();
111
112 // Determine whether to add the given region to the CSet chooser or
113 // not. Currently, we skip pinned regions and regions whose live
114 // bytes are over the threshold. Humongous regions may be reclaimed during cleanup.
115 // Regions also need a complete remembered set to be a candidate.
116 bool should_add(HeapRegion* hr) const;
117
118 // Returns the number candidate old regions added
119 uint length() { return _end; }
120
121 // Serial version.
122 void add_region(HeapRegion *hr);
123
124 // Must be called before calls to claim_array_chunk().
125 // n_regions is the number of regions, chunk_size the chunk size.
126 void prepare_for_par_region_addition(uint n_threads, uint n_regions, uint chunk_size);
127 // Returns the first index in a contiguous chunk of chunk_size indexes
128 // that the calling thread has reserved. These must be set by the
129 // calling thread using set_region() (to NULL if necessary).
130 uint claim_array_chunk(uint chunk_size);
131 // Set the marked array entry at index to hr. Careful to claim the index
132 // first if in parallel.
133 void set_region(uint index, HeapRegion* hr);
134 // Atomically increment the number of added regions by region_num
135 // and the amount of reclaimable bytes by reclaimable_bytes.
136 void update_totals(uint region_num, size_t reclaimable_bytes);
137
138 // Iterate over all collection set candidate regions.
139 void iterate(HeapRegionClosure* cl);
140
141 void clear();
142
143 void rebuild(WorkGang* workers, uint n_regions);
144
145 // Return the number of candidate regions that remain to be collected.
146 uint remaining_regions() { return _end - _front; }
147
148 // Determine whether the CSet chooser has more candidate regions or not.
149 bool is_empty() { return remaining_regions() == 0; }
150
151 // Return the reclaimable bytes that remain to be collected on
152 // all the candidate regions in the CSet chooser.
153 size_t remaining_reclaimable_bytes() { return _remaining_reclaimable_bytes; }
154
155 // Returns true if the used portion of "_regions" is properly
156 // sorted, otherwise asserts false.
157 void verify() PRODUCT_RETURN;
158 };
159
160 class CSetChooserParUpdater : public StackObj {
161 private:
162 CollectionSetChooser* _chooser;
163 bool _parallel;
164 uint _chunk_size;
165 uint _cur_chunk_idx;
166 uint _cur_chunk_end;
167 uint _regions_added;
168 size_t _reclaimable_bytes_added;
169
170 public:
171 CSetChooserParUpdater(CollectionSetChooser* chooser,
172 bool parallel, uint chunk_size) :
173 _chooser(chooser), _parallel(parallel), _chunk_size(chunk_size),
174 _cur_chunk_idx(0), _cur_chunk_end(0),
175 _regions_added(0), _reclaimable_bytes_added(0) { }
176
177 ~CSetChooserParUpdater() {
178 if (_parallel && _regions_added > 0) {
179 _chooser->update_totals(_regions_added, _reclaimable_bytes_added);
180 }
181 }
182
183 void add_region(HeapRegion* hr) {
184 if (_parallel) {
185 if (_cur_chunk_idx == _cur_chunk_end) {
186 _cur_chunk_idx = _chooser->claim_array_chunk(_chunk_size);
187 _cur_chunk_end = _cur_chunk_idx + _chunk_size;
188 }
189 assert(_cur_chunk_idx < _cur_chunk_end, "invariant");
190 _chooser->set_region(_cur_chunk_idx, hr);
191 _cur_chunk_idx += 1;
192 } else {
193 _chooser->add_region(hr);
194 }
195 _regions_added += 1;
196 _reclaimable_bytes_added += hr->reclaimable_bytes();
197 }
198
199 bool should_add(HeapRegion* hr) { return _chooser->should_add(hr); }
200 };
201
202 #endif // SHARE_GC_G1_COLLECTIONSETCHOOSER_HPP
|
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_GC_G1_COLLECTIONSETCHOOSER_HPP
26 #define SHARE_GC_G1_COLLECTIONSETCHOOSER_HPP
27
28 #include "gc/g1/heapRegion.hpp"
29 #include "memory/allocation.hpp"
30 #include "runtime/globals.hpp"
31
32 class G1CollectionSetCandidates;
33 class WorkGang;
34
35 // Helper class to calculate collection set candidates, and containing some related
36 // methods.
37 class CollectionSetChooser : public AllStatic {
38 static uint calculate_work_chunk_size(uint num_workers, uint num_regions);
39 public:
40 CollectionSetChooser();
41
42 static size_t mixed_gc_live_threshold_bytes() {
43 return HeapRegion::GrainBytes * (size_t) G1MixedGCLiveThresholdPercent / 100;
44 }
45
46 static bool region_occupancy_low_enough_for_evac(size_t live_bytes) {
47 return live_bytes < mixed_gc_live_threshold_bytes();
48 }
49
50 // Determine whether to add the given region to the collection set candidates or
51 // not. Currently, we skip pinned regions and regions whose live
52 // bytes are over the threshold. Humongous regions may be reclaimed during cleanup.
53 // Regions also need a complete remembered set to be a candidate.
54 static bool should_add(HeapRegion* hr);
55
56 // Build and return set of collection set candidates sorted by decreasing gc
57 // efficiency.
58 static G1CollectionSetCandidates* build(WorkGang* workers, uint max_num_regions);
59 };
60
61 #endif // SHARE_GC_G1_COLLECTIONSETCHOOSER_HPP
|