1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
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
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23 */
24
25 #ifndef SHARE_VM_GC_G1_COLLECTIONSETCHOOSER_HPP
26 #define SHARE_VM_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 _curr_index;
52
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;
57
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;
61
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;
66
67 // The sum of reclaimable bytes over all the regions in the CSet chooser.
68 size_t _remaining_reclaimable_bytes;
69
70 public:
71
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 }
84
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 }
100
101 CollectionSetChooser();
102
103 void sort_regions();
104
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 archive regions,
108 // which are both "pinned", and regions whose live bytes are over the
109 // threshold.
110 bool should_add(HeapRegion* hr) {
111 assert(hr->is_marked(), "pre-condition");
112 assert(!hr->is_young(), "should never consider young regions");
113 return !hr->is_pinned() &&
114 hr->live_bytes() < _region_live_threshold_bytes;
115 }
116
117 // Returns the number candidate old regions added
118 uint length() { return _length; }
119
120 // Serial version.
121 void add_region(HeapRegion *hr);
122
123 // Must be called before calls to claim_array_chunk().
124 // n_regions is the number of regions, chunk_size the chunk size.
125 void prepare_for_par_region_addition(uint n_threads, uint n_regions, uint chunk_size);
126 // Returns the first index in a contiguous chunk of chunk_size indexes
127 // that the calling thread has reserved. These must be set by the
128 // calling thread using set_region() (to NULL if necessary).
129 uint claim_array_chunk(uint chunk_size);
130 // Set the marked array entry at index to hr. Careful to claim the index
131 // first if in parallel.
132 void set_region(uint index, HeapRegion* hr);
133 // Atomically increment the number of added regions by region_num
134 // and the amount of reclaimable bytes by reclaimable_bytes.
135 void update_totals(uint region_num, size_t reclaimable_bytes);
136
137 void clear();
138
139 // Return the number of candidate regions that remain to be collected.
140 uint remaining_regions() { return _length - _curr_index; }
141
142 // Determine whether the CSet chooser has more candidate regions or not.
143 bool is_empty() { return remaining_regions() == 0; }
144
145 // Return the reclaimable bytes that remain to be collected on
146 // all the candidate regions in the CSet chooser.
147 size_t remaining_reclaimable_bytes() { return _remaining_reclaimable_bytes; }
148
149 // Returns true if the used portion of "_regions" is properly
150 // sorted, otherwise asserts false.
151 void verify() PRODUCT_RETURN;
152 };
153
154 class CSetChooserParUpdater : public StackObj {
155 private:
156 CollectionSetChooser* _chooser;
157 bool _parallel;
158 uint _chunk_size;
159 uint _cur_chunk_idx;
160 uint _cur_chunk_end;
161 uint _regions_added;
162 size_t _reclaimable_bytes_added;
163
164 public:
165 CSetChooserParUpdater(CollectionSetChooser* chooser,
166 bool parallel, uint chunk_size) :
167 _chooser(chooser), _parallel(parallel), _chunk_size(chunk_size),
168 _cur_chunk_idx(0), _cur_chunk_end(0),
169 _regions_added(0), _reclaimable_bytes_added(0) { }
170
171 ~CSetChooserParUpdater() {
172 if (_parallel && _regions_added > 0) {
173 _chooser->update_totals(_regions_added, _reclaimable_bytes_added);
174 }
175 }
176
177 void add_region(HeapRegion* hr) {
178 if (_parallel) {
179 if (_cur_chunk_idx == _cur_chunk_end) {
180 _cur_chunk_idx = _chooser->claim_array_chunk(_chunk_size);
181 _cur_chunk_end = _cur_chunk_idx + _chunk_size;
182 }
183 assert(_cur_chunk_idx < _cur_chunk_end, "invariant");
184 _chooser->set_region(_cur_chunk_idx, hr);
185 _cur_chunk_idx += 1;
186 } else {
187 _chooser->add_region(hr);
188 }
189 _regions_added += 1;
190 _reclaimable_bytes_added += hr->reclaimable_bytes();
191 }
192
193 bool should_add(HeapRegion* hr) { return _chooser->should_add(hr); }
194 };
195
196 #endif // SHARE_VM_GC_G1_COLLECTIONSETCHOOSER_HPP
197