1 /*
2 * Copyright (c) 2016, 2018, Red Hat, Inc. All rights reserved.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This code is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
11 * version 2 for more details (a copy is included in the LICENSE file that
12 * accompanied this code).
13 *
14 * You should have received a copy of the GNU General Public License version
15 * 2 along with this work; if not, write to the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17 *
18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19 * or visit www.oracle.com if you need additional information or have any
20 * questions.
21 *
22 */
23
24 #include "precompiled.hpp"
25
26 #include "gc_implementation/shenandoah/shenandoahCollectionSet.hpp"
27 #include "gc_implementation/shenandoah/shenandoahHeap.inline.hpp"
28 #include "gc_implementation/shenandoah/shenandoahHeapRegion.inline.hpp"
29 #include "gc_implementation/shenandoah/shenandoahHeapRegionSet.hpp"
30 #include "gc_implementation/shenandoah/shenandoahUtils.hpp"
31 #include "runtime/atomic.hpp"
32 #include "services/memTracker.hpp"
33 #include "utilities/copy.hpp"
34
35 ShenandoahCollectionSet::ShenandoahCollectionSet(ShenandoahHeap* heap, ReservedSpace space, char* heap_base) :
36 _map_size(heap->num_regions()),
37 _region_size_bytes_shift(ShenandoahHeapRegion::region_size_bytes_shift()),
38 _map_space(space),
39 _cset_map(_map_space.base() + ((uintx)heap_base >> _region_size_bytes_shift)),
40 _biased_cset_map(_map_space.base()),
41 _heap(heap),
42 _garbage(0),
43 _used(0),
44 _region_count(0),
45 _current_index(0) {
46
47 // The collection set map is reserved to cover the entire heap *and* zero addresses.
48 // This is needed to accept in-cset checks for both heap oops and NULLs, freeing
49 // high-performance code from checking for NULL first.
50 //
51 // Since heap_base can be far away, committing the entire map would waste memory.
52 // Therefore, we only commit the parts that are needed to operate: the heap view,
53 // and the zero page.
54 //
55 // Note: we could instead commit the entire map, and piggyback on OS virtual memory
56 // subsystem for mapping not-yet-written-to pages to a single physical backing page,
57 // but this is not guaranteed, and would confuse NMT and other memory accounting tools.
58
59 MemTracker::record_virtual_memory_type(_map_space.base(), mtGC);
60
61 size_t page_size = (size_t)os::vm_page_size();
62
63 if (!_map_space.special()) {
64 // Commit entire pages that cover the heap cset map.
65 char* bot_addr = (char*)align_ptr_down(_cset_map, page_size);
66 char* top_addr = (char*)align_ptr_up(_cset_map + _map_size, page_size);
67 os::commit_memory_or_exit(bot_addr, pointer_delta(top_addr, bot_addr, 1), false,
68 "Unable to commit collection set bitmap: heap");
69
70 // Commit the zero page, if not yet covered by heap cset map.
71 if (bot_addr != _biased_cset_map) {
72 os::commit_memory_or_exit(_biased_cset_map, page_size, false,
73 "Unable to commit collection set bitmap: zero page");
74 }
75 }
76
77 Copy::zero_to_bytes(_cset_map, _map_size);
78 Copy::zero_to_bytes(_biased_cset_map, page_size);
79 }
80
81 void ShenandoahCollectionSet::add_region(ShenandoahHeapRegion* r) {
82 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
83 assert(Thread::current()->is_VM_thread(), "Must be VMThread");
84 assert(!is_in(r), "Already in collection set");
85 _cset_map[r->index()] = 1;
86 _region_count++;
87 _garbage += r->garbage();
88 _used += r->used();
89
90 // Update the region status too. State transition would be checked internally.
91 r->make_cset();
92 }
93
94 void ShenandoahCollectionSet::clear() {
95 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
96 Copy::zero_to_bytes(_cset_map, _map_size);
97
98 #ifdef ASSERT
99 for (size_t index = 0; index < _heap->num_regions(); index ++) {
100 assert (!_heap->get_region(index)->is_cset(), "should have been cleared before");
101 }
102 #endif
103
104 _garbage = 0;
105 _used = 0;
106
107 _region_count = 0;
108 _current_index = 0;
109 }
110
111 ShenandoahHeapRegion* ShenandoahCollectionSet::claim_next() {
112 size_t num_regions = _heap->num_regions();
113 if (_current_index >= (jint)num_regions) {
114 return NULL;
115 }
116
117 jint saved_current = _current_index;
118 size_t index = (size_t)saved_current;
119
120 while(index < num_regions) {
121 if (is_in(index)) {
122 jint cur = Atomic::cmpxchg((jint)(index + 1), &_current_index, saved_current);
123 assert(cur >= (jint)saved_current, "Must move forward");
124 if (cur == saved_current) {
125 assert(is_in(index), "Invariant");
126 return _heap->get_region(index);
127 } else {
128 index = (size_t)cur;
129 saved_current = cur;
130 }
131 } else {
132 index ++;
133 }
134 }
135 return NULL;
136 }
137
138 ShenandoahHeapRegion* ShenandoahCollectionSet::next() {
139 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
140 assert(Thread::current()->is_VM_thread(), "Must be VMThread");
141 size_t num_regions = _heap->num_regions();
142 for (size_t index = (size_t)_current_index; index < num_regions; index ++) {
143 if (is_in(index)) {
144 _current_index = (jint)(index + 1);
145 return _heap->get_region(index);
146 }
147 }
148
149 return NULL;
150 }
151
152 void ShenandoahCollectionSet::print_on(outputStream* out) const {
153 out->print_cr("Collection Set : " SIZE_FORMAT "", count());
154
155 debug_only(size_t regions = 0;)
156 for (size_t index = 0; index < _heap->num_regions(); index ++) {
157 if (is_in(index)) {
158 _heap->get_region(index)->print_on(out);
159 debug_only(regions ++;)
160 }
161 }
162 assert(regions == count(), "Must match");
163 }