1 /*
2 * Copyright (c) 2018, 2025, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2017, Red Hat, Inc. and/or its affiliates.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "cds/cdsConfig.hpp"
27 #include "gc/g1/g1Arguments.hpp"
28 #include "gc/g1/g1CardSet.hpp"
29 #include "gc/g1/g1CardSetContainers.inline.hpp"
30 #include "gc/g1/g1CollectedHeap.inline.hpp"
31 #include "gc/g1/g1HeapRegion.hpp"
32 #include "gc/g1/g1HeapRegionBounds.inline.hpp"
33 #include "gc/g1/g1HeapRegionRemSet.hpp"
34 #include "gc/g1/g1HeapVerifier.hpp"
35 #include "gc/shared/cardTable.hpp"
36 #include "gc/shared/fullGCForwarding.hpp"
37 #include "gc/shared/gcArguments.hpp"
38 #include "gc/shared/workerPolicy.hpp"
39 #include "runtime/globals.hpp"
40 #include "runtime/globals_extension.hpp"
41 #include "runtime/java.hpp"
42
43 static size_t calculate_heap_alignment(size_t space_alignment) {
44 size_t card_table_alignment = CardTable::ct_max_alignment_constraint();
45 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
46 return MAX3(card_table_alignment, space_alignment, page_size);
47 }
48
49 void G1Arguments::initialize_alignments() {
50 // Initialize card size before initializing alignments
51 CardTable::initialize_card_size();
52
53 // Set up the region size and associated fields.
54 //
55 // There is a circular dependency here. We base the region size on the heap
56 // size, but the heap size should be aligned with the region size. To get
57 // around this we use the unaligned values for the heap.
58 G1HeapRegion::setup_heap_region_size(MaxHeapSize);
59
60 SpaceAlignment = G1HeapRegion::GrainBytes;
61 HeapAlignment = calculate_heap_alignment(SpaceAlignment);
62
63 // We need to initialize card set configuration as soon as heap region size is
64 // known as it depends on it and is used really early.
65 initialize_card_set_configuration();
66 // Needs remembered set initialization as the ergonomics are based
67 // on it.
68 if (FLAG_IS_DEFAULT(G1EagerReclaimRemSetThreshold)) {
69 FLAG_SET_ERGO(G1EagerReclaimRemSetThreshold, G1RemSetArrayOfCardsEntries);
70 }
71 // G1 prefers to use conditional card marking to avoid overwriting cards that
72 // have already been found to contain a to-collection set reference. This reduces
73 // refinement effort.
74 if (FLAG_IS_DEFAULT(UseCondCardMark)) {
75 FLAG_SET_ERGO(UseCondCardMark, true);
76 }
77 }
78
79 size_t G1Arguments::conservative_max_heap_alignment() {
80 if (FLAG_IS_DEFAULT(G1HeapRegionSize)) {
81 return G1HeapRegion::max_ergonomics_size();
82 }
83 return G1HeapRegion::max_region_size();
84 }
85
86 void G1Arguments::initialize_verification_types() {
87 if (strlen(VerifyGCType) > 0) {
88 const char delimiter[] = " ,\n";
89 size_t length = strlen(VerifyGCType);
90 char* type_list = NEW_C_HEAP_ARRAY(char, length + 1, mtInternal);
91 strncpy(type_list, VerifyGCType, length + 1);
92 char* save_ptr;
93
94 char* token = strtok_r(type_list, delimiter, &save_ptr);
95 while (token != nullptr) {
96 parse_verification_type(token);
97 token = strtok_r(nullptr, delimiter, &save_ptr);
98 }
99 FREE_C_HEAP_ARRAY(char, type_list);
100 }
101 }
102
103 void G1Arguments::parse_verification_type(const char* type) {
104 if (strcmp(type, "young-normal") == 0) {
105 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyYoungNormal);
106 } else if (strcmp(type, "concurrent-start") == 0) {
107 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyConcurrentStart);
108 } else if (strcmp(type, "mixed") == 0) {
109 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyMixed);
110 } else if (strcmp(type, "young-evac-fail") == 0) {
111 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyYoungEvacFail);
112 } else if (strcmp(type, "remark") == 0) {
113 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyRemark);
114 } else if (strcmp(type, "cleanup") == 0) {
115 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyCleanup);
116 } else if (strcmp(type, "full") == 0) {
117 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyFull);
118 } else {
119 log_warning(gc, verify)("VerifyGCType: '%s' is unknown. Available types are: "
120 "young-normal, young-evac-fail, concurrent-start, mixed, remark, cleanup and full", type);
121 }
122 }
123
124 // Returns the maximum number of workers to be used in a concurrent
125 // phase based on the number of GC workers being used in a STW
126 // phase.
127 static uint scale_concurrent_worker_threads(uint num_gc_workers) {
128 return MAX2((num_gc_workers + 2) / 4, 1U);
129 }
130
131 void G1Arguments::initialize_mark_stack_size() {
132 if (FLAG_IS_DEFAULT(MarkStackSize)) {
133 size_t mark_stack_size = MIN2(MarkStackSizeMax,
134 MAX2(MarkStackSize, (size_t)ConcGCThreads * TASKQUEUE_SIZE));
135 FLAG_SET_ERGO(MarkStackSize, mark_stack_size);
136 }
137 }
138
139 void G1Arguments::initialize_card_set_configuration() {
140 assert(G1HeapRegion::LogOfHRGrainBytes != 0, "not initialized");
141 // Array of Cards card set container globals.
142 const uint LOG_M = 20;
143 assert(log2i_exact(G1HeapRegionBounds::min_size()) == LOG_M, "inv");
144 assert(G1HeapRegion::LogOfHRGrainBytes >= LOG_M, "from the above");
145 uint region_size_log_mb = G1HeapRegion::LogOfHRGrainBytes - LOG_M;
146
147 if (FLAG_IS_DEFAULT(G1RemSetArrayOfCardsEntries)) {
148 uint max_cards_in_inline_ptr = G1CardSetConfiguration::max_cards_in_inline_ptr(G1HeapRegion::LogCardsPerRegion);
149 FLAG_SET_ERGO(G1RemSetArrayOfCardsEntries, MAX2(max_cards_in_inline_ptr * 2,
150 G1RemSetArrayOfCardsEntriesBase << region_size_log_mb));
151 }
152
153 // Howl card set container globals.
154 if (FLAG_IS_DEFAULT(G1RemSetHowlNumBuckets)) {
155 FLAG_SET_ERGO(G1RemSetHowlNumBuckets, G1CardSetHowl::num_buckets(G1HeapRegion::CardsPerRegion,
156 G1RemSetArrayOfCardsEntries,
157 G1RemSetHowlMaxNumBuckets));
158 }
159
160 if (FLAG_IS_DEFAULT(G1RemSetHowlMaxNumBuckets)) {
161 FLAG_SET_ERGO(G1RemSetHowlMaxNumBuckets, MAX2(G1RemSetHowlMaxNumBuckets, G1RemSetHowlNumBuckets));
162 } else if (G1RemSetHowlMaxNumBuckets < G1RemSetHowlNumBuckets) {
163 FormatBuffer<> buf("Maximum Howl card set container bucket size %u smaller than requested bucket size %u",
164 G1RemSetHowlMaxNumBuckets, G1RemSetHowlNumBuckets);
165 vm_exit_during_initialization(buf);
166 }
167 }
168
169 void G1Arguments::initialize() {
170 GCArguments::initialize();
171 assert(UseG1GC, "Error");
172 FLAG_SET_DEFAULT(ParallelGCThreads, WorkerPolicy::parallel_worker_threads());
173 if (ParallelGCThreads == 0) {
174 assert(!FLAG_IS_DEFAULT(ParallelGCThreads), "The default value for ParallelGCThreads should not be 0.");
175 vm_exit_during_initialization("The flag -XX:+UseG1GC can not be combined with -XX:ParallelGCThreads=0", nullptr);
176 }
177
178 // When dumping the CDS heap we want to reduce fragmentation by
179 // triggering a full collection. To get as low fragmentation as
180 // possible we only use one worker thread.
181 if (CDSConfig::is_dumping_heap()) {
182 FLAG_SET_ERGO(ParallelGCThreads, 1);
183 }
184
185 if (!G1UseConcRefinement) {
186 if (!FLAG_IS_DEFAULT(G1ConcRefinementThreads)) {
187 log_warning(gc, ergo)("Ignoring -XX:G1ConcRefinementThreads "
188 "because of -XX:-G1UseConcRefinement");
189 }
190 FLAG_SET_DEFAULT(G1ConcRefinementThreads, 0);
191 } else if (FLAG_IS_DEFAULT(G1ConcRefinementThreads)) {
192 FLAG_SET_ERGO(G1ConcRefinementThreads, ParallelGCThreads);
193 }
194
195 if (FLAG_IS_DEFAULT(ConcGCThreads) || ConcGCThreads == 0) {
196 // Calculate the number of concurrent worker threads by scaling
197 // the number of parallel GC threads.
198 uint marking_thread_num = scale_concurrent_worker_threads(ParallelGCThreads);
199 FLAG_SET_ERGO(ConcGCThreads, marking_thread_num);
200 }
201
202 if (FLAG_IS_DEFAULT(GCTimeRatio) || GCTimeRatio == 0) {
203 // In G1, we want the default GC overhead goal to be higher than
204 // it is for PS, or the heap might be expanded too aggressively.
205 // We set it here to 4%.
206 FLAG_SET_DEFAULT(GCTimeRatio, 24);
207 }
208
209 // Below, we might need to calculate the pause time interval based on
210 // the pause target. When we do so we are going to give G1 maximum
211 // flexibility and allow it to do pauses when it needs to. So, we'll
212 // arrange that the pause interval to be pause time target + 1 to
213 // ensure that a) the pause time target is maximized with respect to
214 // the pause interval and b) we maintain the invariant that pause
215 // time target < pause interval. If the user does not want this
216 // maximum flexibility, they will have to set the pause interval
217 // explicitly.
218
219 if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
220 // The default pause time target in G1 is 200ms
221 FLAG_SET_DEFAULT(MaxGCPauseMillis, 200);
222 }
223
224 // Then, if the interval parameter was not set, set it according to
225 // the pause time target (this will also deal with the case when the
226 // pause time target is the default value).
227 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
228 FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
229 }
230
231 if (FLAG_IS_DEFAULT(ParallelRefProcEnabled) && ParallelGCThreads > 1) {
232 FLAG_SET_DEFAULT(ParallelRefProcEnabled, true);
233 }
234
235 #ifdef COMPILER2
236 // Enable loop strip mining to offer better pause time guarantees
237 if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) {
238 FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true);
239 if (FLAG_IS_DEFAULT(LoopStripMiningIter)) {
240 FLAG_SET_DEFAULT(LoopStripMiningIter, 1000);
241 }
242 }
243 #endif
244
245 initialize_mark_stack_size();
246 initialize_verification_types();
247
248 // Verify that the maximum parallelism isn't too high to eventually overflow
249 // the refcount in G1CardSetContainer.
250 uint const divisor = 3; // Safe divisor; we increment by 2 for each claim, but there is a small initial value.
251 if (G1ConcRefinementThreads > UINT_MAX / divisor) {
252 vm_exit_during_initialization("Too large parallelism for remembered sets.");
253 }
254
255 FullGCForwarding::initialize_flags(heap_reserved_size_bytes());
256 }
257
258 CollectedHeap* G1Arguments::create_heap() {
259 return new G1CollectedHeap();
260 }
261
262 size_t G1Arguments::heap_reserved_size_bytes() {
263 return MaxHeapSize;
264 }