1 /*
2 * Copyright (c) 2018, Red Hat, Inc. and/or its affiliates.
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/shared/gcArguments.inline.hpp"
27 #include "gc/shenandoah/shenandoahArguments.hpp"
28 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
29 #include "gc/shenandoah/shenandoahHeap.hpp"
30 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
31 #include "gc/shenandoah/shenandoahTaskqueue.hpp"
32 #include "utilities/defaultStream.hpp"
33
34 void ShenandoahArguments::initialize() {
35
36 #if !(defined AARCH64 || defined AMD64 || defined IA32)
37 vm_exit_during_initialization("Shenandoah GC is not supported on this platform.");
38 #endif
39
40 #ifdef IA32
41 log_warning(gc)("Shenandoah GC is not fully supported on this platform:");
42 log_warning(gc)(" concurrent modes are not supported, only STW cycles are enabled;");
43 log_warning(gc)(" arch-specific barrier code is not implemented, disabling barriers;");
44
45 FLAG_SET_DEFAULT(ShenandoahGCHeuristics, "passive");
46
47 FLAG_SET_DEFAULT(ShenandoahSATBBarrier, false);
48 FLAG_SET_DEFAULT(ShenandoahKeepAliveBarrier, false);
49 FLAG_SET_DEFAULT(ShenandoahWriteBarrier, false);
50 FLAG_SET_DEFAULT(ShenandoahReadBarrier, false);
51 FLAG_SET_DEFAULT(ShenandoahStoreValEnqueueBarrier, false);
52 FLAG_SET_DEFAULT(ShenandoahStoreValReadBarrier, false);
53 FLAG_SET_DEFAULT(ShenandoahCASBarrier, false);
54 FLAG_SET_DEFAULT(ShenandoahAcmpBarrier, false);
55 FLAG_SET_DEFAULT(ShenandoahCloneBarrier, false);
56 #endif
57
58 #ifdef _LP64
59 // The optimized ObjArrayChunkedTask takes some bits away from the full 64 addressable
60 // bits, fail if we ever attempt to address more than we can. Only valid on 64bit.
61 if (MaxHeapSize >= ObjArrayChunkedTask::max_addressable()) {
62 jio_fprintf(defaultStream::error_stream(),
63 "Shenandoah GC cannot address more than " SIZE_FORMAT " bytes, and " SIZE_FORMAT " bytes heap requested.",
64 ObjArrayChunkedTask::max_addressable(), MaxHeapSize);
65 vm_exit(1);
66 }
67 #endif
68
69 if (UseLargePages && (MaxHeapSize / os::large_page_size()) < ShenandoahHeapRegion::MIN_NUM_REGIONS) {
70 warning("Large pages size (" SIZE_FORMAT "K) is too large to afford page-sized regions, disabling uncommit",
71 os::large_page_size() / K);
72 FLAG_SET_DEFAULT(ShenandoahUncommit, false);
73 }
74
75 FLAG_SET_DEFAULT(ParallelGCThreads,
76 Abstract_VM_Version::parallel_worker_threads());
77
78 if (FLAG_IS_DEFAULT(ConcGCThreads)) {
79 uint conc_threads = MAX2((uint) 1, ParallelGCThreads);
80 FLAG_SET_DEFAULT(ConcGCThreads, conc_threads);
81 }
82
83 if (FLAG_IS_DEFAULT(ParallelRefProcEnabled)) {
84 FLAG_SET_DEFAULT(ParallelRefProcEnabled, true);
85 }
86
87 if (ShenandoahRegionSampling && FLAG_IS_DEFAULT(PerfDataMemorySize)) {
88 // When sampling is enabled, max out the PerfData memory to get more
89 // Shenandoah data in, including Matrix.
90 FLAG_SET_DEFAULT(PerfDataMemorySize, 2048*K);
91 }
92
93 #ifdef COMPILER2
94 // Shenandoah cares more about pause times, rather than raw throughput.
95 if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) {
96 FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true);
97 if (FLAG_IS_DEFAULT(LoopStripMiningIter)) {
98 FLAG_SET_DEFAULT(LoopStripMiningIter, 1000);
99 }
100 }
101 #ifdef ASSERT
102 // C2 barrier verification is only reliable when all default barriers are enabled
103 if (ShenandoahVerifyOptoBarriers &&
104 (!FLAG_IS_DEFAULT(ShenandoahSATBBarrier) ||
105 !FLAG_IS_DEFAULT(ShenandoahKeepAliveBarrier) ||
106 !FLAG_IS_DEFAULT(ShenandoahWriteBarrier) ||
107 !FLAG_IS_DEFAULT(ShenandoahReadBarrier) ||
108 !FLAG_IS_DEFAULT(ShenandoahStoreValEnqueueBarrier) ||
109 !FLAG_IS_DEFAULT(ShenandoahStoreValReadBarrier) ||
110 !FLAG_IS_DEFAULT(ShenandoahCASBarrier) ||
111 !FLAG_IS_DEFAULT(ShenandoahAcmpBarrier) ||
112 !FLAG_IS_DEFAULT(ShenandoahCloneBarrier)
113 )) {
114 warning("Unusual barrier configuration, disabling C2 barrier verification");
115 FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
116 }
117 #else
118 guarantee(!ShenandoahVerifyOptoBarriers, "Should be disabled");
119 #endif // ASSERT
120 #endif // COMPILER2
121
122 if (AlwaysPreTouch) {
123 // Shenandoah handles pre-touch on its own. It does not let the
124 // generic storage code to do the pre-touch before Shenandoah has
125 // a chance to do it on its own.
126 FLAG_SET_DEFAULT(AlwaysPreTouch, false);
127 FLAG_SET_DEFAULT(ShenandoahAlwaysPreTouch, true);
128 }
129
130 // Shenandoah C2 optimizations apparently dislike the shape of thread-local handshakes.
131 // Disable it by default, unless we enable it specifically for debugging.
132 if (FLAG_IS_DEFAULT(ThreadLocalHandshakes)) {
133 if (ThreadLocalHandshakes) {
134 FLAG_SET_DEFAULT(ThreadLocalHandshakes, false);
135 }
136 } else {
137 if (ThreadLocalHandshakes) {
138 warning("Thread-local handshakes are not working correctly with Shenandoah at the moment. Enable at your own risk.");
139 }
140 }
141
142 // Record more information about previous cycles for improved debugging pleasure
143 if (FLAG_IS_DEFAULT(LogEventsBufferEntries)) {
144 FLAG_SET_DEFAULT(LogEventsBufferEntries, 250);
145 }
146
147 if (ShenandoahAlwaysPreTouch) {
148 if (!FLAG_IS_DEFAULT(ShenandoahUncommit)) {
149 warning("AlwaysPreTouch is enabled, disabling ShenandoahUncommit");
150 }
151 FLAG_SET_DEFAULT(ShenandoahUncommit, false);
152 }
153
154 // If class unloading is disabled, no unloading for concurrent cycles as well.
155 // If class unloading is enabled, users should opt-in for unloading during
156 // concurrent cycles.
157 if (!ClassUnloading || !FLAG_IS_CMDLINE(ClassUnloadingWithConcurrentMark)) {
158 log_info(gc)("Consider -XX:+ClassUnloadingWithConcurrentMark if large pause times "
159 "are observed on class-unloading sensitive workloads");
160 FLAG_SET_DEFAULT(ClassUnloadingWithConcurrentMark, false);
161 }
162
163 // AOT is not supported yet
164 if (UseAOT) {
165 if (!FLAG_IS_DEFAULT(UseAOT)) {
166 warning("Shenandoah does not support AOT at this moment, disabling UseAOT");
167 }
168 FLAG_SET_DEFAULT(UseAOT, false);
169 }
170
171 // JNI fast get field stuff is not currently supported by Shenandoah.
172 // It would introduce another heap memory access for reading the forwarding
173 // pointer, which would have to be guarded by the signal handler machinery.
174 // See:
175 // http://mail.openjdk.java.net/pipermail/hotspot-dev/2018-June/032763.html
176 FLAG_SET_DEFAULT(UseFastJNIAccessors, false);
177
178 // TLAB sizing policy makes resizing decisions before each GC cycle. It averages
179 // historical data, assigning more recent data the weight according to TLABAllocationWeight.
180 // Current default is good for generational collectors that run frequent young GCs.
181 // With Shenandoah, GC cycles are much less frequent, so we need we need sizing policy
182 // to converge faster over smaller number of resizing decisions.
183 if (FLAG_IS_DEFAULT(TLABAllocationWeight)) {
184 FLAG_SET_DEFAULT(TLABAllocationWeight, 90);
185 }
186
187 // Shenandoah needs more C2 nodes to compile some methods with lots of barriers.
188 // NodeLimitFudgeFactor needs to stay the same relative to MaxNodeLimit.
189 #ifdef COMPILER2
190 if (FLAG_IS_DEFAULT(MaxNodeLimit)) {
191 FLAG_SET_DEFAULT(MaxNodeLimit, MaxNodeLimit * 3);
192 FLAG_SET_DEFAULT(NodeLimitFudgeFactor, NodeLimitFudgeFactor * 3);
193 }
194 #endif
195
196 if (ShenandoahLoadRefBarrier) {
197 // TODO: Disabled because not supported yet. Please implement.
198 FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
199 }
200 }
201
202 size_t ShenandoahArguments::conservative_max_heap_alignment() {
203 size_t align = ShenandoahMaxRegionSize;
204 if (UseLargePages) {
205 align = MAX2(align, os::large_page_size());
206 }
207 return align;
208 }
209
210 CollectedHeap* ShenandoahArguments::create_heap() {
211 return create_heap_with_policy<ShenandoahHeap, ShenandoahCollectorPolicy>();
212 }