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.
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23 */
24
25#include "precompiled.hpp"
26#include "gc/shared/gcArguments.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 "utilities/defaultStream.hpp"
33
34void ShenandoahArguments::initialize() {
35#if !(defined AARCH64 || defined AMD64 || defined IA32)
36 vm_exit_during_initialization("Shenandoah GC is not supported on this platform.");
37#endif
38
39#if 0 // leave this block as stepping stone for future platforms
40 log_warning(gc)("Shenandoah GC is not fully supported on this platform:");
41 log_warning(gc)(" concurrent modes are not supported, only STW cycles are enabled;");
42 log_warning(gc)(" arch-specific barrier code is not implemented, disabling barriers;");
43
44 FLAG_SET_DEFAULT(ShenandoahGCHeuristics, "passive");
45
46 FLAG_SET_DEFAULT(ShenandoahSATBBarrier, false);
47 FLAG_SET_DEFAULT(ShenandoahLoadRefBarrier, false);
48 FLAG_SET_DEFAULT(ShenandoahKeepAliveBarrier, false);
49 FLAG_SET_DEFAULT(ShenandoahStoreValEnqueueBarrier, false);
50 FLAG_SET_DEFAULT(ShenandoahCASBarrier, false);
51 FLAG_SET_DEFAULT(ShenandoahCloneBarrier, false);
52
53 FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
54#endif
55
56 if (UseLargePages && (MaxHeapSize / os::large_page_size()) < ShenandoahHeapRegion::MIN_NUM_REGIONS) {
57 warning("Large pages size (" SIZE_FORMAT "K) is too large to afford page-sized regions, disabling uncommit",
58 os::large_page_size() / K);
59 FLAG_SET_DEFAULT(ShenandoahUncommit, false);
60 }
61
62 // Enable NUMA by default. While Shenandoah is not NUMA-aware, enabling NUMA makes
63 // storage allocation code NUMA-aware, and NUMA interleaving makes the storage
64 // allocated in consistent manner (interleaving) to minimize run-to-run variance.
65 if (FLAG_IS_DEFAULT(UseNUMA)) {
66 FLAG_SET_DEFAULT(UseNUMA, true);
67 FLAG_SET_DEFAULT(UseNUMAInterleaving, true);
68 }
69
70 // Set up default number of concurrent threads. We want to have cycles complete fast
71 // enough, but we also do not want to steal too much CPU from the concurrently running
72 // application. Using 1/4 of available threads for concurrent GC seems a good
73 // compromise here.
74 if (FLAG_IS_DEFAULT(ConcGCThreads)) {
75 FLAG_SET_DEFAULT(ConcGCThreads, MAX2(1, os::processor_count() / 4));
76 }
77
78 if (ConcGCThreads == 0) {
79 vm_exit_during_initialization("Shenandoah expects ConcGCThreads > 0, check -XX:ConcGCThreads=#");
80 }
81
82 // Set up default number of parallel threads. We want to have decent pauses performance
83 // which would use parallel threads, but we also do not want to do too many threads
84 // that will overwhelm the OS scheduler. Using 1/2 of available threads seems to be a fair
85 // compromise here. Due to implementation constraints, it should not be lower than
86 // the number of concurrent threads.
87 if (FLAG_IS_DEFAULT(ParallelGCThreads)) {
88 FLAG_SET_DEFAULT(ParallelGCThreads, MAX2(1, os::processor_count() / 2));
89 }
90
91 if (ParallelGCThreads == 0) {
92 vm_exit_during_initialization("Shenandoah expects ParallelGCThreads > 0, check -XX:ParallelGCThreads=#");
93 }
94
95 if (ParallelGCThreads < ConcGCThreads) {
96 warning("Shenandoah expects ConcGCThreads <= ParallelGCThreads, adjusting ParallelGCThreads automatically");
97 FLAG_SET_DEFAULT(ParallelGCThreads, ConcGCThreads);
98 }
99
100 if (FLAG_IS_DEFAULT(ParallelRefProcEnabled)) {
101 FLAG_SET_DEFAULT(ParallelRefProcEnabled, true);
102 }
103
104 if (ShenandoahRegionSampling && FLAG_IS_DEFAULT(PerfDataMemorySize)) {
105 // When sampling is enabled, max out the PerfData memory to get more
106 // Shenandoah data in, including Matrix.
107 FLAG_SET_DEFAULT(PerfDataMemorySize, 2048*K);
108 }
109
110#ifdef COMPILER2
111 // Shenandoah cares more about pause times, rather than raw throughput.
112 if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) {
113 FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true);
114 if (FLAG_IS_DEFAULT(LoopStripMiningIter)) {
115 FLAG_SET_DEFAULT(LoopStripMiningIter, 1000);
116 }
117 }
118#ifdef ASSERT
119 // C2 barrier verification is only reliable when all default barriers are enabled
120 if (ShenandoahVerifyOptoBarriers &&
121 (!FLAG_IS_DEFAULT(ShenandoahSATBBarrier) ||
122 !FLAG_IS_DEFAULT(ShenandoahLoadRefBarrier) ||
123 !FLAG_IS_DEFAULT(ShenandoahKeepAliveBarrier) ||
124 !FLAG_IS_DEFAULT(ShenandoahStoreValEnqueueBarrier) ||
125 !FLAG_IS_DEFAULT(ShenandoahCASBarrier) ||
126 !FLAG_IS_DEFAULT(ShenandoahCloneBarrier)
127 )) {
128 warning("Unusual barrier configuration, disabling C2 barrier verification");
129 FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
130 }
131#else
132 guarantee(!ShenandoahVerifyOptoBarriers, "Should be disabled");
133#endif // ASSERT
134#endif // COMPILER2
135
136 if (AlwaysPreTouch) {
137 // Shenandoah handles pre-touch on its own. It does not let the
138 // generic storage code to do the pre-touch before Shenandoah has
139 // a chance to do it on its own.
140 FLAG_SET_DEFAULT(AlwaysPreTouch, false);
141 FLAG_SET_DEFAULT(ShenandoahAlwaysPreTouch, true);
142 }
143
144 // Record more information about previous cycles for improved debugging pleasure
145 if (FLAG_IS_DEFAULT(LogEventsBufferEntries)) {
146 FLAG_SET_DEFAULT(LogEventsBufferEntries, 250);
147 }
148
149 if (ShenandoahAlwaysPreTouch) {
150 if (!FLAG_IS_DEFAULT(ShenandoahUncommit)) {
151 warning("AlwaysPreTouch is enabled, disabling ShenandoahUncommit");
152 }
153 FLAG_SET_DEFAULT(ShenandoahUncommit, false);
154 }
155
156 if ((InitialHeapSize == MaxHeapSize) && ShenandoahUncommit) {
157 log_info(gc)("Min heap equals to max heap, disabling ShenandoahUncommit");
158 FLAG_SET_DEFAULT(ShenandoahUncommit, false);
159 }
160
161 // If class unloading is disabled, no unloading for concurrent cycles as well.
162 // If class unloading is enabled, users should opt-in for unloading during
163 // concurrent cycles.
164 if (!ClassUnloading || !FLAG_IS_CMDLINE(ClassUnloadingWithConcurrentMark)) {
165 log_info(gc)("Consider -XX:+ClassUnloadingWithConcurrentMark if large pause times "
166 "are observed on class-unloading sensitive workloads");
167 FLAG_SET_DEFAULT(ClassUnloadingWithConcurrentMark, false);
168 }
169
170 // AOT is not supported yet
171 if (UseAOT) {
172 if (!FLAG_IS_DEFAULT(UseAOT)) {
173 warning("Shenandoah does not support AOT at this moment, disabling UseAOT");
174 }
175 FLAG_SET_DEFAULT(UseAOT, false);
176 }
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 // Make sure safepoint deadlocks are failing predictably. This sets up VM to report
197 // fatal error after 10 seconds of wait for safepoint syncronization (not the VM
198 // operation itself). There is no good reason why Shenandoah would spend that
199 // much time synchronizing.
200#ifdef ASSERT
201 FLAG_SET_DEFAULT(SafepointTimeout, true);
202 FLAG_SET_DEFAULT(SafepointTimeoutDelay, 10000);
203 FLAG_SET_DEFAULT(AbortVMOnSafepointTimeout, true);
204#endif
205}
206
207size_t ShenandoahArguments::conservative_max_heap_alignment() {
208 size_t align = ShenandoahMaxRegionSize;
209 if (UseLargePages) {
210 align = MAX2(align, os::large_page_size());
211 }
212 return align;
213}
214
215void ShenandoahArguments::initialize_alignments() {
216 // Need to setup sizes early to get correct alignments.
217 ShenandoahHeapRegion::setup_sizes(MaxHeapSize);
218
219 // This is expected by our algorithm for ShenandoahHeap::heap_region_containing().
220 size_t align = ShenandoahHeapRegion::region_size_bytes();
221 if (UseLargePages) {
222 align = MAX2(align, os::large_page_size());
223 }
224 SpaceAlignment = align;
225 HeapAlignment = align;
226}
227
228CollectedHeap* ShenandoahArguments::create_heap() {
229 return new ShenandoahHeap(new ShenandoahCollectorPolicy());
230}
231