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/gcArguments.hpp"
37 #include "gc/shared/workerPolicy.hpp"
38 #include "runtime/globals.hpp"
39 #include "runtime/globals_extension.hpp"
40 #include "runtime/java.hpp"
41
42 static size_t calculate_heap_alignment(size_t space_alignment) {
43 size_t card_table_alignment = CardTable::ct_max_alignment_constraint();
44 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
45 return MAX3(card_table_alignment, space_alignment, page_size);
46 }
47
48 void G1Arguments::initialize_alignments() {
49 // Initialize card size before initializing alignments
50 CardTable::initialize_card_size();
51
52 // Set up the region size and associated fields.
53 //
54 // There is a circular dependency here. We base the region size on the heap
55 // size, but the heap size should be aligned with the region size. To get
56 // around this we use the unaligned values for the heap.
57 G1HeapRegion::setup_heap_region_size(MaxHeapSize);
58
59 SpaceAlignment = G1HeapRegion::GrainBytes;
60 HeapAlignment = calculate_heap_alignment(SpaceAlignment);
61
62 // We need to initialize card set configuration as soon as heap region size is
63 // known as it depends on it and is used really early.
64 initialize_card_set_configuration();
65 // Needs remembered set initialization as the ergonomics are based
66 // on it.
67 if (FLAG_IS_DEFAULT(G1EagerReclaimRemSetThreshold)) {
68 FLAG_SET_ERGO(G1EagerReclaimRemSetThreshold, G1RemSetArrayOfCardsEntries);
69 }
70 // G1 prefers to use conditional card marking to avoid overwriting cards that
71 // have already been found to contain a to-collection set reference. This reduces
72 // refinement effort.
73 if (FLAG_IS_DEFAULT(UseCondCardMark)) {
74 FLAG_SET_ERGO(UseCondCardMark, true);
75 }
76 }
77
78 size_t G1Arguments::conservative_max_heap_alignment() {
79 if (FLAG_IS_DEFAULT(G1HeapRegionSize)) {
80 return G1HeapRegion::max_ergonomics_size();
81 }
82 return G1HeapRegion::max_region_size();
83 }
84
85 void G1Arguments::initialize_verification_types() {
86 if (strlen(VerifyGCType) > 0) {
87 const char delimiter[] = " ,\n";
88 size_t length = strlen(VerifyGCType);
89 char* type_list = NEW_C_HEAP_ARRAY(char, length + 1, mtInternal);
90 strncpy(type_list, VerifyGCType, length + 1);
91 char* save_ptr;
92
93 char* token = strtok_r(type_list, delimiter, &save_ptr);
94 while (token != nullptr) {
95 parse_verification_type(token);
96 token = strtok_r(nullptr, delimiter, &save_ptr);
97 }
98 FREE_C_HEAP_ARRAY(char, type_list);
99 }
100 }
101
102 void G1Arguments::parse_verification_type(const char* type) {
103 if (strcmp(type, "young-normal") == 0) {
104 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyYoungNormal);
105 } else if (strcmp(type, "concurrent-start") == 0) {
106 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyConcurrentStart);
107 } else if (strcmp(type, "mixed") == 0) {
108 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyMixed);
109 } else if (strcmp(type, "young-evac-fail") == 0) {
110 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyYoungEvacFail);
111 } else if (strcmp(type, "remark") == 0) {
112 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyRemark);
113 } else if (strcmp(type, "cleanup") == 0) {
114 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyCleanup);
115 } else if (strcmp(type, "full") == 0) {
116 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyFull);
117 } else {
118 log_warning(gc, verify)("VerifyGCType: '%s' is unknown. Available types are: "
119 "young-normal, young-evac-fail, concurrent-start, mixed, remark, cleanup and full", type);
120 }
121 }
122
123 // Returns the maximum number of workers to be used in a concurrent
124 // phase based on the number of GC workers being used in a STW
125 // phase.
126 static uint scale_concurrent_worker_threads(uint num_gc_workers) {
127 return MAX2((num_gc_workers + 2) / 4, 1U);
128 }
129
130 void G1Arguments::initialize_mark_stack_size() {
131 if (FLAG_IS_DEFAULT(MarkStackSize)) {
132 size_t mark_stack_size = MIN2(MarkStackSizeMax,
133 MAX2(MarkStackSize, (size_t)ConcGCThreads * TASKQUEUE_SIZE));
134 FLAG_SET_ERGO(MarkStackSize, mark_stack_size);
135 }
136 }
137
138 void G1Arguments::initialize_card_set_configuration() {
139 assert(G1HeapRegion::LogOfHRGrainBytes != 0, "not initialized");
140 // Array of Cards card set container globals.
141 const uint LOG_M = 20;
142 assert(log2i_exact(G1HeapRegionBounds::min_size()) == LOG_M, "inv");
143 assert(G1HeapRegion::LogOfHRGrainBytes >= LOG_M, "from the above");
144 uint region_size_log_mb = G1HeapRegion::LogOfHRGrainBytes - LOG_M;
145
146 if (FLAG_IS_DEFAULT(G1RemSetArrayOfCardsEntries)) {
147 uint max_cards_in_inline_ptr = G1CardSetConfiguration::max_cards_in_inline_ptr(G1HeapRegion::LogCardsPerRegion);
148 FLAG_SET_ERGO(G1RemSetArrayOfCardsEntries, MAX2(max_cards_in_inline_ptr * 2,
149 G1RemSetArrayOfCardsEntriesBase << region_size_log_mb));
150 }
151
152 // Howl card set container globals.
153 if (FLAG_IS_DEFAULT(G1RemSetHowlNumBuckets)) {
154 FLAG_SET_ERGO(G1RemSetHowlNumBuckets, G1CardSetHowl::num_buckets(G1HeapRegion::CardsPerRegion,
155 G1RemSetArrayOfCardsEntries,
156 G1RemSetHowlMaxNumBuckets));
157 }
158
159 if (FLAG_IS_DEFAULT(G1RemSetHowlMaxNumBuckets)) {
160 FLAG_SET_ERGO(G1RemSetHowlMaxNumBuckets, MAX2(G1RemSetHowlMaxNumBuckets, G1RemSetHowlNumBuckets));
161 } else if (G1RemSetHowlMaxNumBuckets < G1RemSetHowlNumBuckets) {
162 FormatBuffer<> buf("Maximum Howl card set container bucket size %u smaller than requested bucket size %u",
163 G1RemSetHowlMaxNumBuckets, G1RemSetHowlNumBuckets);
164 vm_exit_during_initialization(buf);
165 }
166 }
167
168 void G1Arguments::initialize() {
169 GCArguments::initialize();
170 assert(UseG1GC, "Error");
171 FLAG_SET_DEFAULT(ParallelGCThreads, WorkerPolicy::parallel_worker_threads());
172 if (ParallelGCThreads == 0) {
173 assert(!FLAG_IS_DEFAULT(ParallelGCThreads), "The default value for ParallelGCThreads should not be 0.");
174 vm_exit_during_initialization("The flag -XX:+UseG1GC can not be combined with -XX:ParallelGCThreads=0", nullptr);
175 }
176
177 // When dumping the CDS heap we want to reduce fragmentation by
178 // triggering a full collection. To get as low fragmentation as
179 // possible we only use one worker thread.
180 if (CDSConfig::is_dumping_heap()) {
181 FLAG_SET_ERGO(ParallelGCThreads, 1);
182 }
183
184 if (!G1UseConcRefinement) {
185 if (!FLAG_IS_DEFAULT(G1ConcRefinementThreads)) {
186 log_warning(gc, ergo)("Ignoring -XX:G1ConcRefinementThreads "
187 "because of -XX:-G1UseConcRefinement");
188 }
189 FLAG_SET_DEFAULT(G1ConcRefinementThreads, 0);
190 } else if (FLAG_IS_DEFAULT(G1ConcRefinementThreads)) {
191 FLAG_SET_ERGO(G1ConcRefinementThreads, ParallelGCThreads);
192 }
193
194 if (FLAG_IS_DEFAULT(ConcGCThreads) || ConcGCThreads == 0) {
195 // Calculate the number of concurrent worker threads by scaling
196 // the number of parallel GC threads.
197 uint marking_thread_num = scale_concurrent_worker_threads(ParallelGCThreads);
198 FLAG_SET_ERGO(ConcGCThreads, marking_thread_num);
199 }
200
201 if (FLAG_IS_DEFAULT(GCTimeRatio) || GCTimeRatio == 0) {
202 // In G1, we want the default GC overhead goal to be higher than
203 // it is for PS, or the heap might be expanded too aggressively.
204 // We set it here to 4%.
205 FLAG_SET_DEFAULT(GCTimeRatio, 24);
206 }
207
208 // Below, we might need to calculate the pause time interval based on
209 // the pause target. When we do so we are going to give G1 maximum
210 // flexibility and allow it to do pauses when it needs to. So, we'll
211 // arrange that the pause interval to be pause time target + 1 to
212 // ensure that a) the pause time target is maximized with respect to
213 // the pause interval and b) we maintain the invariant that pause
214 // time target < pause interval. If the user does not want this
215 // maximum flexibility, they will have to set the pause interval
216 // explicitly.
217
218 if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
219 // The default pause time target in G1 is 200ms
220 FLAG_SET_DEFAULT(MaxGCPauseMillis, 200);
221 }
222
223 // Then, if the interval parameter was not set, set it according to
224 // the pause time target (this will also deal with the case when the
225 // pause time target is the default value).
226 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
227 FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
228 }
229
230 if (FLAG_IS_DEFAULT(ParallelRefProcEnabled) && ParallelGCThreads > 1) {
231 FLAG_SET_DEFAULT(ParallelRefProcEnabled, true);
232 }
233
234 #ifdef COMPILER2
235 // Enable loop strip mining to offer better pause time guarantees
236 if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) {
237 FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true);
238 if (FLAG_IS_DEFAULT(LoopStripMiningIter)) {
239 FLAG_SET_DEFAULT(LoopStripMiningIter, 1000);
240 }
241 }
242 #endif
243
244 initialize_mark_stack_size();
245 initialize_verification_types();
246
247 // Verify that the maximum parallelism isn't too high to eventually overflow
248 // the refcount in G1CardSetContainer.
249 uint const divisor = 3; // Safe divisor; we increment by 2 for each claim, but there is a small initial value.
250 if (G1ConcRefinementThreads > UINT_MAX / divisor) {
251 vm_exit_during_initialization("Too large parallelism for remembered sets.");
252 }
253 }
254
255 CollectedHeap* G1Arguments::create_heap() {
256 return new G1CollectedHeap();
257 }
258
259 size_t G1Arguments::heap_reserved_size_bytes() {
260 return MaxHeapSize;
261 }