1 /*
2 * Copyright (c) 2018, 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/cms/cmsArguments.hpp"
28 #include "gc/cms/cmsCollectorPolicy.hpp"
29 #include "gc/cms/cmsHeap.hpp"
30 #include "gc/cms/compactibleFreeListSpace.hpp"
31 #include "gc/shared/gcArguments.inline.hpp"
32 #include "gc/shared/genCollectedHeap.hpp"
33 #include "gc/shared/workerPolicy.hpp"
34 #include "runtime/arguments.hpp"
35 #include "runtime/globals.hpp"
36 #include "runtime/globals_extension.hpp"
37 #include "utilities/defaultStream.hpp"
38
39 size_t CMSArguments::conservative_max_heap_alignment() {
40 return GenCollectedHeap::conservative_max_heap_alignment();
41 }
42
43 void CMSArguments::set_parnew_gc_flags() {
44 assert(!UseSerialGC && !UseParallelOldGC && !UseParallelGC && !UseG1GC,
45 "control point invariant");
46 assert(UseConcMarkSweepGC, "CMS is expected to be on here");
47
48 if (FLAG_IS_DEFAULT(ParallelGCThreads)) {
49 FLAG_SET_DEFAULT(ParallelGCThreads, WorkerPolicy::parallel_worker_threads());
50 assert(ParallelGCThreads > 0, "We should always have at least one thread by default");
51 } else if (ParallelGCThreads == 0) {
52 jio_fprintf(defaultStream::error_stream(),
53 "The ParNew GC can not be combined with -XX:ParallelGCThreads=0\n");
54 vm_exit(1);
55 }
56
57 // By default YoungPLABSize and OldPLABSize are set to 4096 and 1024 respectively,
58 // these settings are default for Parallel Scavenger. For ParNew+Tenured configuration
59 // we set them to 1024 and 1024.
60 // See CR 6362902.
61 if (FLAG_IS_DEFAULT(YoungPLABSize)) {
62 FLAG_SET_DEFAULT(YoungPLABSize, (intx)1024);
63 }
64 if (FLAG_IS_DEFAULT(OldPLABSize)) {
65 FLAG_SET_DEFAULT(OldPLABSize, (intx)1024);
66 }
67
68 // When using compressed oops, we use local overflow stacks,
69 // rather than using a global overflow list chained through
70 // the klass word of the object's pre-image.
71 if (UseCompressedOops && !ParGCUseLocalOverflow) {
72 if (!FLAG_IS_DEFAULT(ParGCUseLocalOverflow)) {
73 warning("Forcing +ParGCUseLocalOverflow: needed if using compressed references");
74 }
75 FLAG_SET_DEFAULT(ParGCUseLocalOverflow, true);
76 }
77 assert(ParGCUseLocalOverflow || !UseCompressedOops, "Error");
78 }
79
80 // Adjust some sizes to suit CMS and/or ParNew needs; these work well on
81 // sparc/solaris for certain applications, but would gain from
82 // further optimization and tuning efforts, and would almost
83 // certainly gain from analysis of platform and environment.
84 void CMSArguments::initialize() {
85 GCArguments::initialize();
86
87 assert(!UseSerialGC && !UseParallelOldGC && !UseParallelGC, "Error");
88 assert(UseConcMarkSweepGC, "CMS is expected to be on here");
89
90 // CMS space iteration, which FLSVerifyAllHeapreferences entails,
91 // insists that we hold the requisite locks so that the iteration is
92 // MT-safe. For the verification at start-up and shut-down, we don't
93 // yet have a good way of acquiring and releasing these locks,
94 // which are not visible at the CollectedHeap level. We want to
95 // be able to acquire these locks and then do the iteration rather
96 // than just disable the lock verification. This will be fixed under
97 // bug 4788986.
98 if (UseConcMarkSweepGC && FLSVerifyAllHeapReferences) {
99 if (VerifyDuringStartup) {
100 warning("Heap verification at start-up disabled "
101 "(due to current incompatibility with FLSVerifyAllHeapReferences)");
102 VerifyDuringStartup = false; // Disable verification at start-up
103 }
104
105 if (VerifyBeforeExit) {
106 warning("Heap verification at shutdown disabled "
107 "(due to current incompatibility with FLSVerifyAllHeapReferences)");
108 VerifyBeforeExit = false; // Disable verification at shutdown
109 }
110 }
111
112 if (!ClassUnloading) {
113 FLAG_SET_CMDLINE(bool, CMSClassUnloadingEnabled, false);
114 }
115
116 // Set CMS global values
117 CompactibleFreeListSpace::set_cms_values();
118
119 // Turn off AdaptiveSizePolicy by default for cms until it is complete.
120 disable_adaptive_size_policy("UseConcMarkSweepGC");
121
122 set_parnew_gc_flags();
123
124 size_t max_heap = align_down(MaxHeapSize,
125 CardTableRS::ct_max_alignment_constraint());
126
127 // Now make adjustments for CMS
128 intx tenuring_default = (intx)6;
129 size_t young_gen_per_worker = CMSYoungGenPerWorker;
130
131 // Preferred young gen size for "short" pauses:
132 // upper bound depends on # of threads and NewRatio.
133 const size_t preferred_max_new_size_unaligned =
134 MIN2(max_heap/(NewRatio+1), ScaleForWordSize(young_gen_per_worker * ParallelGCThreads));
135 size_t preferred_max_new_size =
136 align_up(preferred_max_new_size_unaligned, os::vm_page_size());
137
138 // Unless explicitly requested otherwise, size young gen
139 // for "short" pauses ~ CMSYoungGenPerWorker*ParallelGCThreads
140
141 // If either MaxNewSize or NewRatio is set on the command line,
142 // assume the user is trying to set the size of the young gen.
143 if (FLAG_IS_DEFAULT(MaxNewSize) && FLAG_IS_DEFAULT(NewRatio)) {
144
145 // Set MaxNewSize to our calculated preferred_max_new_size unless
146 // NewSize was set on the command line and it is larger than
147 // preferred_max_new_size.
148 if (!FLAG_IS_DEFAULT(NewSize)) { // NewSize explicitly set at command-line
149 FLAG_SET_ERGO(size_t, MaxNewSize, MAX2(NewSize, preferred_max_new_size));
150 } else {
151 FLAG_SET_ERGO(size_t, MaxNewSize, preferred_max_new_size);
152 }
153 log_trace(gc, heap)("CMS ergo set MaxNewSize: " SIZE_FORMAT, MaxNewSize);
154
155 // Code along this path potentially sets NewSize and OldSize
156 log_trace(gc, heap)("CMS set min_heap_size: " SIZE_FORMAT " initial_heap_size: " SIZE_FORMAT " max_heap: " SIZE_FORMAT,
157 Arguments::min_heap_size(), InitialHeapSize, max_heap);
158 size_t min_new = preferred_max_new_size;
159 if (FLAG_IS_CMDLINE(NewSize)) {
160 min_new = NewSize;
161 }
162 if (max_heap > min_new && Arguments::min_heap_size() > min_new) {
163 // Unless explicitly requested otherwise, make young gen
164 // at least min_new, and at most preferred_max_new_size.
165 if (FLAG_IS_DEFAULT(NewSize)) {
166 FLAG_SET_ERGO(size_t, NewSize, MAX2(NewSize, min_new));
167 FLAG_SET_ERGO(size_t, NewSize, MIN2(preferred_max_new_size, NewSize));
168 log_trace(gc, heap)("CMS ergo set NewSize: " SIZE_FORMAT, NewSize);
169 }
170 // Unless explicitly requested otherwise, size old gen
171 // so it's NewRatio x of NewSize.
172 if (FLAG_IS_DEFAULT(OldSize)) {
173 if (max_heap > NewSize) {
174 FLAG_SET_ERGO(size_t, OldSize, MIN2(NewRatio*NewSize, max_heap - NewSize));
175 log_trace(gc, heap)("CMS ergo set OldSize: " SIZE_FORMAT, OldSize);
176 }
177 }
178 }
179 }
180 // Unless explicitly requested otherwise, definitely
181 // promote all objects surviving "tenuring_default" scavenges.
182 if (FLAG_IS_DEFAULT(MaxTenuringThreshold) &&
183 FLAG_IS_DEFAULT(SurvivorRatio)) {
184 FLAG_SET_ERGO(uintx, MaxTenuringThreshold, tenuring_default);
185 }
186 // If we decided above (or user explicitly requested)
187 // `promote all' (via MaxTenuringThreshold := 0),
188 // prefer minuscule survivor spaces so as not to waste
189 // space for (non-existent) survivors
190 if (FLAG_IS_DEFAULT(SurvivorRatio) && MaxTenuringThreshold == 0) {
191 FLAG_SET_ERGO(uintx, SurvivorRatio, MAX2((uintx)1024, SurvivorRatio));
192 }
193
194 // OldPLABSize is interpreted in CMS as not the size of the PLAB in words,
195 // but rather the number of free blocks of a given size that are used when
196 // replenishing the local per-worker free list caches.
197 if (FLAG_IS_DEFAULT(OldPLABSize)) {
198 if (!FLAG_IS_DEFAULT(ResizeOldPLAB) && !ResizeOldPLAB) {
199 // OldPLAB sizing manually turned off: Use a larger default setting,
200 // unless it was manually specified. This is because a too-low value
201 // will slow down scavenges.
202 FLAG_SET_ERGO(size_t, OldPLABSize, CompactibleFreeListSpaceLAB::_default_static_old_plab_size); // default value before 6631166
203 } else {
204 FLAG_SET_DEFAULT(OldPLABSize, CompactibleFreeListSpaceLAB::_default_dynamic_old_plab_size); // old CMSParPromoteBlocksToClaim default
205 }
206 }
207
208 // If either of the static initialization defaults have changed, note this
209 // modification.
210 if (!FLAG_IS_DEFAULT(OldPLABSize) || !FLAG_IS_DEFAULT(OldPLABWeight)) {
211 CompactibleFreeListSpaceLAB::modify_initialization(OldPLABSize, OldPLABWeight);
212 }
213
214 log_trace(gc)("MarkStackSize: %uk MarkStackSizeMax: %uk", (unsigned int) (MarkStackSize / K), (uint) (MarkStackSizeMax / K));
215 }
216
217 void CMSArguments::disable_adaptive_size_policy(const char* collector_name) {
218 if (UseAdaptiveSizePolicy) {
219 if (FLAG_IS_CMDLINE(UseAdaptiveSizePolicy)) {
220 warning("Disabling UseAdaptiveSizePolicy; it is incompatible with %s.",
221 collector_name);
222 }
223 FLAG_SET_DEFAULT(UseAdaptiveSizePolicy, false);
224 }
225 }
226
227 CollectedHeap* CMSArguments::create_heap() {
228 return create_heap_with_policy<CMSHeap, ConcurrentMarkSweepPolicy>();
229 }