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/shenandoah/shenandoahArguments.hpp"
28 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
29 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
30 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
31 #include "utilities/defaultStream.hpp"
32
33 void ShenandoahArguments::initialize() {
34 #if !(defined AARCH64 || defined AMD64 || defined IA32)
35 vm_exit_during_initialization("Shenandoah GC is not supported on this platform.");
36 #endif
37
38 #if 0 // leave this block as stepping stone for future platforms
39 log_warning(gc)("Shenandoah GC is not fully supported on this platform:");
40 log_warning(gc)(" concurrent modes are not supported, only STW cycles are enabled;");
41 log_warning(gc)(" arch-specific barrier code is not implemented, disabling barriers;");
42
43 FLAG_SET_DEFAULT(ShenandoahGCHeuristics, "passive");
44
45 FLAG_SET_DEFAULT(ShenandoahSATBBarrier, false);
46 FLAG_SET_DEFAULT(ShenandoahLoadRefBarrier, false);
47 FLAG_SET_DEFAULT(ShenandoahKeepAliveBarrier, false);
48 FLAG_SET_DEFAULT(ShenandoahStoreValEnqueueBarrier, false);
49 FLAG_SET_DEFAULT(ShenandoahCASBarrier, false);
50 FLAG_SET_DEFAULT(ShenandoahCloneBarrier, false);
51
52 FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
53 #endif
54
55 if (UseLargePages && (MaxHeapSize / os::large_page_size()) < ShenandoahHeapRegion::MIN_NUM_REGIONS) {
56 warning("Large pages size (" SIZE_FORMAT "K) is too large to afford page-sized regions, disabling uncommit",
57 os::large_page_size() / K);
58 FLAG_SET_DEFAULT(ShenandoahUncommit, false);
59 }
60
61 // Enable NUMA by default. While Shenandoah is not NUMA-aware, enabling NUMA makes
62 // storage allocation code NUMA-aware.
63 if (FLAG_IS_DEFAULT(UseNUMA)) {
64 FLAG_SET_DEFAULT(UseNUMA, true);
65 }
66
67 // Set up default number of concurrent threads. We want to have cycles complete fast
68 // enough, but we also do not want to steal too much CPU from the concurrently running
69 // application. Using 1/4 of available threads for concurrent GC seems a good
70 // compromise here.
71 bool ergo_conc = FLAG_IS_DEFAULT(ConcGCThreads);
72 if (ergo_conc) {
73 FLAG_SET_DEFAULT(ConcGCThreads, MAX2(1, os::processor_count() / 4));
74 }
75
76 if (ConcGCThreads == 0) {
77 vm_exit_during_initialization("Shenandoah expects ConcGCThreads > 0, check -XX:ConcGCThreads=#");
78 }
79
80 // Set up default number of parallel threads. We want to have decent pauses performance
81 // which would use parallel threads, but we also do not want to do too many threads
82 // that will overwhelm the OS scheduler. Using 1/2 of available threads seems to be a fair
83 // compromise here. Due to implementation constraints, it should not be lower than
84 // the number of concurrent threads.
85 bool ergo_parallel = FLAG_IS_DEFAULT(ParallelGCThreads);
86 if (ergo_parallel) {
87 FLAG_SET_DEFAULT(ParallelGCThreads, MAX2(1, os::processor_count() / 2));
88 }
89
90 if (ParallelGCThreads == 0) {
91 vm_exit_during_initialization("Shenandoah expects ParallelGCThreads > 0, check -XX:ParallelGCThreads=#");
92 }
93
94 // Make sure ergonomic decisions do not break the thread count invariants.
95 // This may happen when user overrides one of the flags, but not the other.
96 // When that happens, we want to adjust the setting that was set ergonomically.
97 if (ParallelGCThreads < ConcGCThreads) {
98 if (ergo_conc && !ergo_parallel) {
99 FLAG_SET_DEFAULT(ConcGCThreads, ParallelGCThreads);
100 } else if (!ergo_conc && ergo_parallel) {
101 FLAG_SET_DEFAULT(ParallelGCThreads, ConcGCThreads);
102 } else if (ergo_conc && ergo_parallel) {
103 // Should not happen, check the ergonomic computation above. Fail with relevant error.
104 vm_exit_during_initialization("Shenandoah thread count ergonomic error");
105 } else {
106 // User settings error, report and ask user to rectify.
107 vm_exit_during_initialization("Shenandoah expects ConcGCThreads <= ParallelGCThreads, check -XX:ParallelGCThreads, -XX:ConcGCThreads");
108 }
109 }
110
111 if (FLAG_IS_DEFAULT(ParallelRefProcEnabled)) {
112 FLAG_SET_DEFAULT(ParallelRefProcEnabled, true);
113 }
114
115 if (ShenandoahRegionSampling && FLAG_IS_DEFAULT(PerfDataMemorySize)) {
116 // When sampling is enabled, max out the PerfData memory to get more
117 // Shenandoah data in, including Matrix.
118 FLAG_SET_DEFAULT(PerfDataMemorySize, 2048*K);
119 }
120
121 #ifdef COMPILER2
122 // Shenandoah cares more about pause times, rather than raw throughput.
123 if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) {
124 FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true);
125 if (FLAG_IS_DEFAULT(LoopStripMiningIter)) {
126 FLAG_SET_DEFAULT(LoopStripMiningIter, 1000);
127 }
128 }
129 #ifdef ASSERT
130 // C2 barrier verification is only reliable when all default barriers are enabled
131 if (ShenandoahVerifyOptoBarriers &&
132 (!FLAG_IS_DEFAULT(ShenandoahSATBBarrier) ||
133 !FLAG_IS_DEFAULT(ShenandoahLoadRefBarrier) ||
134 !FLAG_IS_DEFAULT(ShenandoahKeepAliveBarrier) ||
135 !FLAG_IS_DEFAULT(ShenandoahStoreValEnqueueBarrier) ||
136 !FLAG_IS_DEFAULT(ShenandoahCASBarrier) ||
137 !FLAG_IS_DEFAULT(ShenandoahCloneBarrier)
138 )) {
139 warning("Unusual barrier configuration, disabling C2 barrier verification");
140 FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
141 }
142 #else
143 guarantee(!ShenandoahVerifyOptoBarriers, "Should be disabled");
144 #endif // ASSERT
145 #endif // COMPILER2
146
147 if (AlwaysPreTouch) {
148 // Shenandoah handles pre-touch on its own. It does not let the
149 // generic storage code to do the pre-touch before Shenandoah has
150 // a chance to do it on its own.
151 FLAG_SET_DEFAULT(AlwaysPreTouch, false);
152 FLAG_SET_DEFAULT(ShenandoahAlwaysPreTouch, true);
153 }
154
155 // Shenandoah C2 optimizations apparently dislike the shape of thread-local handshakes.
156 // Disable it by default, unless we enable it specifically for debugging.
157 if (FLAG_IS_DEFAULT(ThreadLocalHandshakes)) {
158 if (ThreadLocalHandshakes) {
159 FLAG_SET_DEFAULT(ThreadLocalHandshakes, false);
160 }
161 } else {
162 if (ThreadLocalHandshakes) {
163 warning("Thread-local handshakes are not working correctly with Shenandoah at the moment. Enable at your own risk.");
164 }
165 }
166
167 // Record more information about previous cycles for improved debugging pleasure
168 if (FLAG_IS_DEFAULT(LogEventsBufferEntries)) {
169 FLAG_SET_DEFAULT(LogEventsBufferEntries, 250);
170 }
171
172 if (ShenandoahAlwaysPreTouch) {
173 if (!FLAG_IS_DEFAULT(ShenandoahUncommit)) {
174 warning("AlwaysPreTouch is enabled, disabling ShenandoahUncommit");
175 }
176 FLAG_SET_DEFAULT(ShenandoahUncommit, false);
177 }
178
179 if ((InitialHeapSize == MaxHeapSize) && ShenandoahUncommit) {
180 log_info(gc)("Min heap equals to max heap, disabling ShenandoahUncommit");
181 FLAG_SET_DEFAULT(ShenandoahUncommit, false);
182 }
183
184 // If class unloading is disabled, no unloading for concurrent cycles as well.
185 // If class unloading is enabled, users should opt-in for unloading during
186 // concurrent cycles.
187 if (!ClassUnloading || !FLAG_IS_CMDLINE(ClassUnloadingWithConcurrentMark)) {
188 log_info(gc)("Consider -XX:+ClassUnloadingWithConcurrentMark if large pause times "
189 "are observed on class-unloading sensitive workloads");
190 FLAG_SET_DEFAULT(ClassUnloadingWithConcurrentMark, false);
191 }
192
193 // AOT is not supported yet
194 if (UseAOT) {
195 if (!FLAG_IS_DEFAULT(UseAOT)) {
196 warning("Shenandoah does not support AOT at this moment, disabling UseAOT");
197 }
198 FLAG_SET_DEFAULT(UseAOT, false);
199 }
200
201 // TLAB sizing policy makes resizing decisions before each GC cycle. It averages
202 // historical data, assigning more recent data the weight according to TLABAllocationWeight.
203 // Current default is good for generational collectors that run frequent young GCs.
204 // With Shenandoah, GC cycles are much less frequent, so we need we need sizing policy
205 // to converge faster over smaller number of resizing decisions.
206 if (FLAG_IS_DEFAULT(TLABAllocationWeight)) {
207 FLAG_SET_DEFAULT(TLABAllocationWeight, 90);
208 }
209
210 // Shenandoah needs more C2 nodes to compile some methods with lots of barriers.
211 // NodeLimitFudgeFactor needs to stay the same relative to MaxNodeLimit.
212 #ifdef COMPILER2
213 if (FLAG_IS_DEFAULT(MaxNodeLimit)) {
214 FLAG_SET_DEFAULT(MaxNodeLimit, MaxNodeLimit * 3);
215 FLAG_SET_DEFAULT(NodeLimitFudgeFactor, NodeLimitFudgeFactor * 3);
216 }
217 #endif
218
219 // Make sure safepoint deadlocks are failing predictably. This sets up VM to report
220 // fatal error after 10 seconds of wait for safepoint syncronization (not the VM
221 // operation itself). There is no good reason why Shenandoah would spend that
222 // much time synchronizing.
223 #ifdef ASSERT
224 FLAG_SET_DEFAULT(SafepointTimeout, true);
225 FLAG_SET_DEFAULT(SafepointTimeoutDelay, 10000);
226 FLAG_SET_DEFAULT(AbortVMOnSafepointTimeout, true);
227 #endif
228 }
229
230 size_t ShenandoahArguments::conservative_max_heap_alignment() {
231 size_t align = ShenandoahMaxRegionSize;
232 if (UseLargePages) {
233 align = MAX2(align, os::large_page_size());
234 }
235 return align;
236 }
237
238 CollectedHeap* ShenandoahArguments::create_heap() {
239 return create_heap_with_policy<ShenandoahHeap, ShenandoahCollectorPolicy>();
240 }