1 /*
2 * Copyright (c) 2018, 2020, 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 "precompiled.hpp"
27 #include "gc/g1/g1Arguments.hpp"
28 #include "gc/g1/g1CollectedHeap.inline.hpp"
29 #include "gc/g1/g1HeapVerifier.hpp"
30 #include "gc/g1/heapRegion.hpp"
31 #include "gc/g1/heapRegionRemSet.hpp"
32 #include "gc/shared/cardTableRS.hpp"
33 #include "gc/shared/gcArguments.hpp"
34 #include "gc/shared/workerPolicy.hpp"
35 #include "runtime/globals.hpp"
36
37 static const double MaxRamFractionForYoung = 0.8;
38 size_t G1Arguments::MaxMemoryForYoung;
39
40 static size_t calculate_heap_alignment(size_t space_alignment) {
41 size_t card_table_alignment = CardTableRS::ct_max_alignment_constraint();
42 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
43 return MAX3(card_table_alignment, space_alignment, page_size);
44 }
45
46 void G1Arguments::initialize_alignments() {
47 // Set up the region size and associated fields.
48 //
49 // There is a circular dependency here. We base the region size on the heap
50 // size, but the heap size should be aligned with the region size. To get
51 // around this we use the unaligned values for the heap.
52 HeapRegion::setup_heap_region_size(MaxHeapSize);
53 HeapRegionRemSet::setup_remset_size();
54
55 SpaceAlignment = HeapRegion::GrainBytes;
56 HeapAlignment = calculate_heap_alignment(SpaceAlignment);
57 }
58
59 size_t G1Arguments::conservative_max_heap_alignment() {
60 return HeapRegion::max_region_size();
61 }
62
63 void G1Arguments::initialize_verification_types() {
64 if (strlen(VerifyGCType) > 0) {
65 const char delimiter[] = " ,\n";
66 size_t length = strlen(VerifyGCType);
67 char* type_list = NEW_C_HEAP_ARRAY(char, length + 1, mtInternal);
68 strncpy(type_list, VerifyGCType, length + 1);
69 char* save_ptr;
70
71 char* token = strtok_r(type_list, delimiter, &save_ptr);
72 while (token != NULL) {
73 parse_verification_type(token);
74 token = strtok_r(NULL, delimiter, &save_ptr);
75 }
76 FREE_C_HEAP_ARRAY(char, type_list);
77 }
78 }
79
80 void G1Arguments::parse_verification_type(const char* type) {
81 if (strcmp(type, "young-normal") == 0) {
82 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyYoungNormal);
83 } else if (strcmp(type, "concurrent-start") == 0) {
84 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyConcurrentStart);
85 } else if (strcmp(type, "mixed") == 0) {
86 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyMixed);
87 } else if (strcmp(type, "remark") == 0) {
88 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyRemark);
89 } else if (strcmp(type, "cleanup") == 0) {
90 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyCleanup);
91 } else if (strcmp(type, "full") == 0) {
92 G1HeapVerifier::enable_verification_type(G1HeapVerifier::G1VerifyFull);
93 } else {
94 log_warning(gc, verify)("VerifyGCType: '%s' is unknown. Available types are: "
95 "young-normal, concurrent-start, mixed, remark, cleanup and full", type);
96 }
97 }
98
99 // Returns the maximum number of workers to be used in a concurrent
100 // phase based on the number of GC workers being used in a STW
101 // phase.
102 static uint scale_concurrent_worker_threads(uint num_gc_workers) {
103 return MAX2((num_gc_workers + 2) / 4, 1U);
104 }
105
106 void G1Arguments::initialize_mark_stack_size() {
107 if (FLAG_IS_DEFAULT(MarkStackSize)) {
108 size_t mark_stack_size = MIN2(MarkStackSizeMax,
109 MAX2(MarkStackSize, (size_t)ConcGCThreads * TASKQUEUE_SIZE));
110 FLAG_SET_ERGO(MarkStackSize, mark_stack_size);
111 }
112
113 log_trace(gc)("MarkStackSize: %uk MarkStackSizeMax: %uk", (uint)(MarkStackSize / K), (uint)(MarkStackSizeMax / K));
114 }
115
116 void G1Arguments::initialize() {
117 GCArguments::initialize();
118 assert(UseG1GC, "Error");
119 FLAG_SET_DEFAULT(ParallelGCThreads, WorkerPolicy::parallel_worker_threads());
120 if (ParallelGCThreads == 0) {
121 assert(!FLAG_IS_DEFAULT(ParallelGCThreads), "The default value for ParallelGCThreads should not be 0.");
122 vm_exit_during_initialization("The flag -XX:+UseG1GC can not be combined with -XX:ParallelGCThreads=0", NULL);
123 }
124
125 // When dumping the CDS archive we want to reduce fragmentation by
126 // triggering a full collection. To get as low fragmentation as
127 // possible we only use one worker thread.
128 if (DumpSharedSpaces) {
129 FLAG_SET_ERGO(ParallelGCThreads, 1);
130 }
131
132 if (FLAG_IS_DEFAULT(G1ConcRefinementThreads)) {
133 FLAG_SET_ERGO(G1ConcRefinementThreads, ParallelGCThreads);
134 }
135
136 if (FLAG_IS_DEFAULT(ConcGCThreads) || ConcGCThreads == 0) {
137 // Calculate the number of concurrent worker threads by scaling
138 // the number of parallel GC threads.
139 uint marking_thread_num = scale_concurrent_worker_threads(ParallelGCThreads);
140 FLAG_SET_ERGO(ConcGCThreads, marking_thread_num);
141 }
142
143 if (FLAG_IS_DEFAULT(GCTimeRatio) || GCTimeRatio == 0) {
144 // In G1, we want the default GC overhead goal to be higher than
145 // it is for PS, or the heap might be expanded too aggressively.
146 // We set it here to ~8%.
147 FLAG_SET_DEFAULT(GCTimeRatio, 12);
148 }
149
150 // Below, we might need to calculate the pause time interval based on
151 // the pause target. When we do so we are going to give G1 maximum
152 // flexibility and allow it to do pauses when it needs to. So, we'll
153 // arrange that the pause interval to be pause time target + 1 to
154 // ensure that a) the pause time target is maximized with respect to
155 // the pause interval and b) we maintain the invariant that pause
156 // time target < pause interval. If the user does not want this
157 // maximum flexibility, they will have to set the pause interval
158 // explicitly.
159
160 if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
161 // The default pause time target in G1 is 200ms
162 FLAG_SET_DEFAULT(MaxGCPauseMillis, 200);
163 }
164
165 // Then, if the interval parameter was not set, set it according to
166 // the pause time target (this will also deal with the case when the
167 // pause time target is the default value).
168 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
169 FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
170 }
171
172 if (FLAG_IS_DEFAULT(ParallelRefProcEnabled) && ParallelGCThreads > 1) {
173 FLAG_SET_DEFAULT(ParallelRefProcEnabled, true);
174 }
175
176 // By default do not let the target stack size to be more than 1/4 of the entries
177 if (FLAG_IS_DEFAULT(GCDrainStackTargetSize)) {
178 FLAG_SET_ERGO(GCDrainStackTargetSize, MIN2(GCDrainStackTargetSize, (uintx)TASKQUEUE_SIZE / 4));
179 }
180
181 #ifdef COMPILER2
182 // Enable loop strip mining to offer better pause time guarantees
183 if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) {
184 FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true);
185 if (FLAG_IS_DEFAULT(LoopStripMiningIter)) {
186 FLAG_SET_DEFAULT(LoopStripMiningIter, 1000);
187 }
188 }
189 #endif
190
191 initialize_mark_stack_size();
192 initialize_verification_types();
193 }
194
195 static size_t calculate_reasonable_max_memory_for_young(FormatBuffer<100> &calc_str, double max_ram_fraction_for_young) {
196 julong phys_mem;
197 // If MaxRam is specified, we use that as maximum physical memory available.
198 if (FLAG_IS_DEFAULT(MaxRAM)) {
199 phys_mem = os::physical_memory();
200 calc_str.append("Physical_Memory");
201 } else {
202 phys_mem = (julong)MaxRAM;
203 calc_str.append("MaxRAM");
204 }
205
206 julong reasonable_max = phys_mem;
207
208 // If either MaxRAMFraction or MaxRAMPercentage is specified, we use them to calculate
209 // reasonable max size of young generation.
210 if (!FLAG_IS_DEFAULT(MaxRAMFraction)) {
211 reasonable_max = (julong)(phys_mem / MaxRAMFraction);
212 calc_str.append(" / MaxRAMFraction");
213 } else if (!FLAG_IS_DEFAULT(MaxRAMPercentage)) {
214 reasonable_max = (julong)((phys_mem * MaxRAMPercentage) / 100);
215 calc_str.append(" * MaxRAMPercentage / 100");
216 } else {
217 // We use our own fraction to calculate max size of young generation.
218 reasonable_max = phys_mem * max_ram_fraction_for_young;
219 calc_str.append(" * %0.2f", max_ram_fraction_for_young);
220 }
221
222 return (size_t)reasonable_max;
223 }
224
225 void G1Arguments::initialize_heap_flags_and_sizes() {
226 if (AllocateOldGenAt != NULL) {
227 initialize_heterogeneous();
228 }
229
230 GCArguments::initialize_heap_flags_and_sizes();
231 }
232
233 void G1Arguments::initialize_heterogeneous() {
234 FormatBuffer<100> calc_str("");
235
236 MaxMemoryForYoung = calculate_reasonable_max_memory_for_young(calc_str, MaxRamFractionForYoung);
237
238 if (MaxNewSize > MaxMemoryForYoung) {
239 if (FLAG_IS_CMDLINE(MaxNewSize)) {
240 log_warning(gc, ergo)("Setting MaxNewSize to " SIZE_FORMAT " based on dram available (calculation = align(%s))",
241 MaxMemoryForYoung, calc_str.buffer());
242 } else {
243 log_info(gc, ergo)("Setting MaxNewSize to " SIZE_FORMAT " based on dram available (calculation = align(%s)). "
244 "Dram usage can be lowered by setting MaxNewSize to a lower value", MaxMemoryForYoung, calc_str.buffer());
245 }
246 MaxNewSize = MaxMemoryForYoung;
247 }
248 if (NewSize > MaxMemoryForYoung) {
249 if (FLAG_IS_CMDLINE(NewSize)) {
250 log_warning(gc, ergo)("Setting NewSize to " SIZE_FORMAT " based on dram available (calculation = align(%s))",
251 MaxMemoryForYoung, calc_str.buffer());
252 }
253 NewSize = MaxMemoryForYoung;
254 }
255
256 }
257
258 CollectedHeap* G1Arguments::create_heap() {
259 return new G1CollectedHeap();
260 }
261
262 bool G1Arguments::is_heterogeneous_heap() {
263 return AllocateOldGenAt != NULL;
264 }
265
266 size_t G1Arguments::reasonable_max_memory_for_young() {
267 return MaxMemoryForYoung;
268 }
269
270 size_t G1Arguments::heap_reserved_size_bytes() {
271 return (is_heterogeneous_heap() ? 2 : 1) * MaxHeapSize;
272 }
273
274 size_t G1Arguments::heap_max_size_bytes() {
275 return MaxHeapSize;
276 }