1 /*
2 * Copyright (c) 2018, 2019, Red Hat, Inc. All rights reserved.
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/shared/workerPolicy.hpp"
28 #include "gc/shenandoah/shenandoahArguments.hpp"
29 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
30 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
31 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
32 #include "gc/shenandoah/shenandoahTaskqueue.hpp"
33 #include "utilities/defaultStream.hpp"
34
35 void ShenandoahArguments::initialize() {
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 // Enable NUMA by default. While Shenandoah is not NUMA-aware, enabling NUMA makes
76 // storage allocation code NUMA-aware, and NUMA interleaving makes the storage
77 // allocated in consistent manner (interleaving) to minimize run-to-run variance.
78 if (FLAG_IS_DEFAULT(UseNUMA)) {
79 FLAG_SET_DEFAULT(UseNUMA, true);
80 FLAG_SET_DEFAULT(UseNUMAInterleaving, true);
81 }
82
83 FLAG_SET_DEFAULT(ParallelGCThreads,
84 WorkerPolicy::parallel_worker_threads());
85
86 if (FLAG_IS_DEFAULT(ConcGCThreads)) {
87 uint conc_threads = MAX2((uint) 1, ParallelGCThreads);
88 FLAG_SET_DEFAULT(ConcGCThreads, conc_threads);
89 }
90
91 if (FLAG_IS_DEFAULT(ParallelRefProcEnabled)) {
92 FLAG_SET_DEFAULT(ParallelRefProcEnabled, true);
93 }
94
95 if (ShenandoahRegionSampling && FLAG_IS_DEFAULT(PerfDataMemorySize)) {
96 // When sampling is enabled, max out the PerfData memory to get more
97 // Shenandoah data in, including Matrix.
98 FLAG_SET_DEFAULT(PerfDataMemorySize, 2048*K);
99 }
100
101 #ifdef COMPILER2
102 // Shenandoah cares more about pause times, rather than raw throughput.
103 if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) {
104 FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true);
105 if (FLAG_IS_DEFAULT(LoopStripMiningIter)) {
106 FLAG_SET_DEFAULT(LoopStripMiningIter, 1000);
107 }
108 }
109 #ifdef ASSERT
110 // C2 barrier verification is only reliable when all default barriers are enabled
111 if (ShenandoahVerifyOptoBarriers &&
112 (!FLAG_IS_DEFAULT(ShenandoahSATBBarrier) ||
113 !FLAG_IS_DEFAULT(ShenandoahKeepAliveBarrier) ||
114 !FLAG_IS_DEFAULT(ShenandoahWriteBarrier) ||
115 !FLAG_IS_DEFAULT(ShenandoahReadBarrier) ||
116 !FLAG_IS_DEFAULT(ShenandoahStoreValEnqueueBarrier) ||
117 !FLAG_IS_DEFAULT(ShenandoahStoreValReadBarrier) ||
118 !FLAG_IS_DEFAULT(ShenandoahCASBarrier) ||
119 !FLAG_IS_DEFAULT(ShenandoahAcmpBarrier) ||
120 !FLAG_IS_DEFAULT(ShenandoahCloneBarrier)
121 )) {
122 warning("Unusual barrier configuration, disabling C2 barrier verification");
123 FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
124 }
125 #else
126 guarantee(!ShenandoahVerifyOptoBarriers, "Should be disabled");
127 #endif // ASSERT
128 #endif // COMPILER2
129
130 if (AlwaysPreTouch) {
131 // Shenandoah handles pre-touch on its own. It does not let the
132 // generic storage code to do the pre-touch before Shenandoah has
133 // a chance to do it on its own.
134 FLAG_SET_DEFAULT(AlwaysPreTouch, false);
135 FLAG_SET_DEFAULT(ShenandoahAlwaysPreTouch, true);
136 }
137
138 // Record more information about previous cycles for improved debugging pleasure
139 if (FLAG_IS_DEFAULT(LogEventsBufferEntries)) {
140 FLAG_SET_DEFAULT(LogEventsBufferEntries, 250);
141 }
142
143 if (ShenandoahAlwaysPreTouch) {
144 if (!FLAG_IS_DEFAULT(ShenandoahUncommit)) {
145 warning("AlwaysPreTouch is enabled, disabling ShenandoahUncommit");
146 }
147 FLAG_SET_DEFAULT(ShenandoahUncommit, false);
148 }
149
150 // If class unloading is disabled, no unloading for concurrent cycles as well.
151 // If class unloading is enabled, users should opt-in for unloading during
152 // concurrent cycles.
153 if (!ClassUnloading || !FLAG_IS_CMDLINE(ClassUnloadingWithConcurrentMark)) {
154 log_info(gc)("Consider -XX:+ClassUnloadingWithConcurrentMark if large pause times "
155 "are observed on class-unloading sensitive workloads");
156 FLAG_SET_DEFAULT(ClassUnloadingWithConcurrentMark, false);
157 }
158
159 // AOT is not supported yet
160 if (UseAOT) {
161 if (!FLAG_IS_DEFAULT(UseAOT)) {
162 warning("Shenandoah does not support AOT at this moment, disabling UseAOT");
163 }
164 FLAG_SET_DEFAULT(UseAOT, false);
165 }
166
167 // JNI fast get field stuff is not currently supported by Shenandoah.
168 // It would introduce another heap memory access for reading the forwarding
169 // pointer, which would have to be guarded by the signal handler machinery.
170 // See:
171 // http://mail.openjdk.java.net/pipermail/hotspot-dev/2018-June/032763.html
172 FLAG_SET_DEFAULT(UseFastJNIAccessors, false);
173
174 // TLAB sizing policy makes resizing decisions before each GC cycle. It averages
175 // historical data, assigning more recent data the weight according to TLABAllocationWeight.
176 // Current default is good for generational collectors that run frequent young GCs.
177 // With Shenandoah, GC cycles are much less frequent, so we need we need sizing policy
178 // to converge faster over smaller number of resizing decisions.
179 if (FLAG_IS_DEFAULT(TLABAllocationWeight)) {
180 FLAG_SET_DEFAULT(TLABAllocationWeight, 90);
181 }
182
183 // Shenandoah needs more C2 nodes to compile some methods with lots of barriers.
184 // NodeLimitFudgeFactor needs to stay the same relative to MaxNodeLimit.
185 #ifdef COMPILER2
186 if (FLAG_IS_DEFAULT(MaxNodeLimit)) {
187 FLAG_SET_DEFAULT(MaxNodeLimit, MaxNodeLimit * 3);
188 FLAG_SET_DEFAULT(NodeLimitFudgeFactor, NodeLimitFudgeFactor * 3);
189 }
190 #endif
191
192 // Make sure safepoint deadlocks are failing predictably. This sets up VM to report
193 // fatal error after 10 seconds of wait for safepoint syncronization (not the VM
194 // operation itself). There is no good reason why Shenandoah would spend that
195 // much time synchronizing.
196 #ifdef ASSERT
197 FLAG_SET_DEFAULT(SafepointTimeout, true);
198 FLAG_SET_DEFAULT(SafepointTimeoutDelay, 10000);
199 FLAG_SET_DEFAULT(AbortVMOnSafepointTimeout, true);
200 #endif
201 }
202
203 size_t ShenandoahArguments::conservative_max_heap_alignment() {
204 size_t align = ShenandoahMaxRegionSize;
205 if (UseLargePages) {
206 align = MAX2(align, os::large_page_size());
207 }
208 return align;
209 }
210
211 CollectedHeap* ShenandoahArguments::create_heap() {
212 return create_heap_with_policy<ShenandoahHeap, ShenandoahCollectorPolicy>();
213 }