1 /*
2 * Copyright (c) 2001, 2023, 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 #include "precompiled.hpp"
26 #include "gc/parallel/mutableSpace.hpp"
27 #include "gc/shared/pretouchTask.hpp"
28 #include "memory/iterator.inline.hpp"
29 #include "memory/universe.hpp"
30 #include "oops/oop.inline.hpp"
31 #include "runtime/atomic.hpp"
32 #include "runtime/javaThread.hpp"
33 #include "runtime/safepoint.hpp"
34 #include "utilities/align.hpp"
35 #include "utilities/macros.hpp"
36
37 MutableSpace::MutableSpace(size_t alignment) :
38 _last_setup_region(),
39 _alignment(alignment),
40 _bottom(nullptr),
41 _top(nullptr),
42 _end(nullptr)
43 {
44 assert(MutableSpace::alignment() % os::vm_page_size() == 0,
45 "Space should be aligned");
46 }
47
48 void MutableSpace::numa_setup_pages(MemRegion mr, size_t page_size, bool clear_space) {
49 if (!mr.is_empty()) {
50 HeapWord *start = align_up(mr.start(), page_size);
51 HeapWord *end = align_down(mr.end(), page_size);
52 if (end > start) {
53 size_t size = pointer_delta(end, start, sizeof(char));
54 if (clear_space) {
55 // Prefer page reallocation to migration.
56 os::free_memory((char*)start, size, page_size);
57 }
58 os::numa_make_global((char*)start, size);
59 }
60 }
61 }
62
63 void MutableSpace::initialize(MemRegion mr,
64 bool clear_space,
65 bool mangle_space,
66 bool setup_pages,
67 WorkerThreads* pretouch_workers) {
68
69 assert(Universe::on_page_boundary(mr.start()) && Universe::on_page_boundary(mr.end()),
70 "invalid space boundaries");
71
72 if (setup_pages && (UseNUMA || AlwaysPreTouch)) {
73 // The space may move left and right or expand/shrink.
74 // We'd like to enforce the desired page placement.
75 MemRegion head, tail;
76 if (last_setup_region().is_empty()) {
77 // If it's the first initialization don't limit the amount of work.
78 head = mr;
79 tail = MemRegion(mr.end(), mr.end());
80 } else {
81 // Is there an intersection with the address space?
82 MemRegion intersection = last_setup_region().intersection(mr);
83 if (intersection.is_empty()) {
84 intersection = MemRegion(mr.end(), mr.end());
85 }
86 // All the sizes below are in words.
87 size_t head_size = 0, tail_size = 0;
88 if (mr.start() <= intersection.start()) {
89 head_size = pointer_delta(intersection.start(), mr.start());
90 }
91 if(intersection.end() <= mr.end()) {
92 tail_size = pointer_delta(mr.end(), intersection.end());
93 }
94 // Limit the amount of page manipulation if necessary.
95 if (NUMASpaceResizeRate > 0 && !AlwaysPreTouch) {
96 const size_t change_size = head_size + tail_size;
97 const float setup_rate_words = NUMASpaceResizeRate >> LogBytesPerWord;
98 head_size = MIN2((size_t)(setup_rate_words * head_size / change_size),
99 head_size);
100 tail_size = MIN2((size_t)(setup_rate_words * tail_size / change_size),
101 tail_size);
102 }
103 head = MemRegion(intersection.start() - head_size, intersection.start());
104 tail = MemRegion(intersection.end(), intersection.end() + tail_size);
105 }
106 assert(mr.contains(head) && mr.contains(tail), "Sanity");
107
108 size_t page_size = alignment();
109
110 if (UseNUMA) {
111 numa_setup_pages(head, page_size, clear_space);
112 numa_setup_pages(tail, page_size, clear_space);
113 }
114
115 if (AlwaysPreTouch) {
116 size_t pretouch_page_size = UseLargePages ? page_size : os::vm_page_size();
117 PretouchTask::pretouch("ParallelGC PreTouch head", (char*)head.start(), (char*)head.end(),
118 pretouch_page_size, pretouch_workers);
119
120 PretouchTask::pretouch("ParallelGC PreTouch tail", (char*)tail.start(), (char*)tail.end(),
121 pretouch_page_size, pretouch_workers);
122 }
123
124 // Remember where we stopped so that we can continue later.
125 set_last_setup_region(MemRegion(head.start(), tail.end()));
126 }
127
128 set_bottom(mr.start());
129 // When expanding concurrently with callers of cas_allocate, setting end
130 // makes the new space available for allocation by other threads. So this
131 // assignment must follow all other configuration and initialization that
132 // might be done for expansion.
133 Atomic::release_store(end_addr(), mr.end());
134
135 if (clear_space) {
136 clear(mangle_space);
137 }
138 }
139
140 void MutableSpace::clear(bool mangle_space) {
141 set_top(bottom());
142 if (ZapUnusedHeapArea && mangle_space) {
143 mangle_unused_area();
144 }
145 }
146
147 #ifndef PRODUCT
148
149 void MutableSpace::mangle_unused_area() {
150 mangle_region(MemRegion(_top, _end));
151 }
152
153 void MutableSpace::mangle_region(MemRegion mr) {
154 SpaceMangler::mangle_region(mr);
155 }
156
157 #endif
158
159 HeapWord* MutableSpace::cas_allocate(size_t size) {
160 do {
161 // Read top before end, else the range check may pass when it shouldn't.
162 // If end is read first, other threads may advance end and top such that
163 // current top > old end and current top + size > current end. Then
164 // pointer_delta underflows, allowing installation of top > current end.
165 HeapWord* obj = Atomic::load_acquire(top_addr());
166 if (pointer_delta(end(), obj) >= size) {
167 HeapWord* new_top = obj + size;
168 HeapWord* result = Atomic::cmpxchg(top_addr(), obj, new_top);
169 // result can be one of two:
170 // the old top value: the exchange succeeded
171 // otherwise: the new value of the top is returned.
172 if (result != obj) {
173 continue; // another thread beat us to the allocation, try again
174 }
175 assert(is_object_aligned(obj) && is_object_aligned(new_top),
176 "checking alignment");
177 return obj;
178 } else {
179 return nullptr;
180 }
181 } while (true);
182 }
183
184 // Try to deallocate previous allocation. Returns true upon success.
185 bool MutableSpace::cas_deallocate(HeapWord *obj, size_t size) {
186 HeapWord* expected_top = obj + size;
187 return Atomic::cmpxchg(top_addr(), expected_top, obj) == expected_top;
188 }
189
190 // Only used by oldgen allocation.
191 bool MutableSpace::needs_expand(size_t word_size) const {
192 assert_lock_strong(PSOldGenExpand_lock);
193 // Holding the lock means end is stable. So while top may be advancing
194 // via concurrent allocations, there is no need to order the reads of top
195 // and end here, unlike in cas_allocate.
196 return pointer_delta(end(), top()) < word_size;
197 }
198
199 void MutableSpace::oop_iterate(OopIterateClosure* cl) {
200 HeapWord* obj_addr = bottom();
201 HeapWord* t = top();
202 // Could call objects iterate, but this is easier.
203 while (obj_addr < t) {
204 obj_addr += cast_to_oop(obj_addr)->oop_iterate_size(cl);
205 }
206 }
207
208 template<bool COMPACT_HEADERS>
209 void MutableSpace::object_iterate_impl(ObjectClosure* cl) {
210 HeapWord* p = bottom();
211 while (p < top()) {
212 oop obj = cast_to_oop(p);
213 // When promotion-failure occurs during Young GC, eden/from space is not cleared,
214 // so we can encounter objects with "forwarded" markword.
215 // They are essentially dead, so skipping them
216 if (!obj->is_forwarded()) {
217 cl->do_object(obj);
218 p += obj->size();
219 } else {
220 assert(obj->forwardee() != obj, "must not be self-forwarded");
221 if (COMPACT_HEADERS) {
222 // It is safe to use the forwardee here. Parallel GC only uses
223 // header-based forwarding during promotion. Full GC doesn't
224 // use the object header for forwarding at all.
225 p += obj->forwardee()->size();
226 } else {
227 p += obj->size();
228 }
229 }
230 }
231 }
232
233 void MutableSpace::object_iterate(ObjectClosure* cl) {
234 if (UseCompactObjectHeaders) {
235 object_iterate_impl<true>(cl);
236 } else {
237 object_iterate_impl<false>(cl);
238 }
239 }
240
241 void MutableSpace::print_short() const { print_short_on(tty); }
242 void MutableSpace::print_short_on( outputStream* st) const {
243 st->print(" space " SIZE_FORMAT "K, %d%% used", capacity_in_bytes() / K,
244 (int) ((double) used_in_bytes() * 100 / capacity_in_bytes()));
245 }
246
247 void MutableSpace::print() const { print_on(tty); }
248 void MutableSpace::print_on(outputStream* st) const {
249 MutableSpace::print_short_on(st);
250 st->print_cr(" [" PTR_FORMAT "," PTR_FORMAT "," PTR_FORMAT ")",
251 p2i(bottom()), p2i(top()), p2i(end()));
252 }
253
254 void MutableSpace::verify() {
255 HeapWord* p = bottom();
256 HeapWord* t = top();
257 while (p < t) {
258 oopDesc::verify(cast_to_oop(p));
259 p += cast_to_oop(p)->size();
260 }
261 guarantee(p == top(), "end of last object must match end of space");
262 }