1 /*
2 * Copyright (c) 2001, 2012, 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
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP
27
28 #include "gc_implementation/g1/heapRegion.hpp"
29 #include "utilities/growableArray.hpp"
30
31 class CollectionSetChooser: public CHeapObj {
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 uint _length;
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 public:
69
70 // Return the current candidate region to be considered for
71 // collection without removing it from the CSet chooser.
72 HeapRegion* peek() {
73 HeapRegion* res = NULL;
74 if (_curr_index < _length) {
75 res = regions_at(_curr_index);
76 assert(res != NULL,
77 err_msg("Unexpected NULL hr in _regions at index %u",
78 _curr_index));
79 }
80 return res;
81 }
82
83 // Remove the given region from the CSet chooser and move to the
84 // next one. The given region should be the current candidate region
85 // in the CSet chooser.
86 void remove_and_move_to_next(HeapRegion* hr) {
87 assert(hr != NULL, "pre-condition");
88 assert(_curr_index < _length, "pre-condition");
89 assert(regions_at(_curr_index) == hr, "pre-condition");
90 regions_at_put(_curr_index, NULL);
91 assert(hr->reclaimable_bytes() <= _remaining_reclaimable_bytes,
92 err_msg("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 _curr_index += 1;
97 }
98
99 CollectionSetChooser();
100
101 void sort_regions();
102
103 // Determine whether to add the given region to the CSet chooser or
104 // not. Currently, we skip humongous regions (we never add them to
105 // the CSet, we only reclaim them during cleanup) and regions whose
106 // live bytes are over the threshold.
107 bool should_add(HeapRegion* hr) {
108 assert(hr->is_marked(), "pre-condition");
109 assert(!hr->is_young(), "should never consider young regions");
110 return !hr->isHumongous() &&
111 hr->live_bytes() < _region_live_threshold_bytes;
112 }
113
114 // Calculate the minimum number of old regions we'll add to the CSet
115 // during a mixed GC.
116 uint calc_min_old_cset_length();
117
118 // Calculate the maximum number of old regions we'll add to the CSet
119 // during a mixed GC.
120 uint calc_max_old_cset_length();
121
122 // Serial version.
123 void add_region(HeapRegion *hr);
124
125 // Must be called before calls to claim_array_chunk().
126 // n_regions is the number of regions, chunk_size the chunk size.
127 void prepare_for_par_region_addition(uint n_regions, uint chunk_size);
128 // Returns the first index in a contiguous chunk of chunk_size indexes
129 // that the calling thread has reserved. These must be set by the
130 // calling thread using set_region() (to NULL if necessary).
131 uint claim_array_chunk(uint chunk_size);
132 // Set the marked array entry at index to hr. Careful to claim the index
133 // first if in parallel.
134 void set_region(uint index, HeapRegion* hr);
135 // Atomically increment the number of added regions by region_num
136 // and the amount of reclaimable bytes by reclaimable_bytes.
137 void update_totals(uint region_num, size_t reclaimable_bytes);
138
139 void clear();
140
141 // Return the number of candidate regions that remain to be collected.
142 uint remaining_regions() { return _length - _curr_index; }
143
144 // Determine whether the CSet chooser has more candidate regions or not.
145 bool is_empty() { return remaining_regions() == 0; }
146
147 // Return the reclaimable bytes that remain to be collected on
148 // all the candidate regions in the CSet chooser.
149 size_t remaining_reclaimable_bytes() { return _remaining_reclaimable_bytes; }
150
151 // Returns true if the used portion of "_regions" is properly
152 // sorted, otherwise asserts false.
153 void verify() PRODUCT_RETURN;
154 };
155
156 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP