1 /*
2 * Copyright (c) 2018, 2022, Red Hat, Inc. All rights reserved.
3 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
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/shared/gcArguments.hpp"
28 #include "gc/shared/tlab_globals.hpp"
29 #include "gc/shared/workerPolicy.hpp"
30 #include "gc/shenandoah/shenandoahArguments.hpp"
31 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
32 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
33 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
34 #include "runtime/globals_extension.hpp"
35 #include "runtime/java.hpp"
36 #include "utilities/defaultStream.hpp"
37
38 void ShenandoahArguments::initialize() {
39 #if !(defined AARCH64 || defined AMD64 || defined IA32 || defined PPC64 || defined RISCV64)
40 vm_exit_during_initialization("Shenandoah GC is not supported on this platform.");
41 #endif
42
43 #if 0 // leave this block as stepping stone for future platforms
44 log_warning(gc)("Shenandoah GC is not fully supported on this platform:");
45 log_warning(gc)(" concurrent modes are not supported, only STW cycles are enabled;");
46 log_warning(gc)(" arch-specific barrier code is not implemented, disabling barriers;");
47
48 FLAG_SET_DEFAULT(ShenandoahGCHeuristics, "passive");
49
50 FLAG_SET_DEFAULT(ShenandoahSATBBarrier, false);
51 FLAG_SET_DEFAULT(ShenandoahLoadRefBarrier, false);
52 FLAG_SET_DEFAULT(ShenandoahIUBarrier, false);
53 FLAG_SET_DEFAULT(ShenandoahCASBarrier, false);
54 FLAG_SET_DEFAULT(ShenandoahCloneBarrier, false);
55
56 FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
57 #endif
58 if (UseLargePages) {
59 size_t large_page_size = os::large_page_size();
60 if ((align_up(MaxHeapSize, large_page_size) / large_page_size) < ShenandoahHeapRegion::MIN_NUM_REGIONS) {
61 warning("Large pages size (" SIZE_FORMAT "K) is too large to afford page-sized regions, disabling uncommit",
62 os::large_page_size() / K);
63 FLAG_SET_DEFAULT(ShenandoahUncommit, false);
64 }
65 }
66
67 // Enable NUMA by default. While Shenandoah is not NUMA-aware, enabling NUMA makes
68 // storage allocation code NUMA-aware.
69 if (FLAG_IS_DEFAULT(UseNUMA)) {
70 FLAG_SET_DEFAULT(UseNUMA, true);
71 }
72
73 // We use this as the time period for tracking minimum mutator utilization (MMU).
74 // In generational mode, the MMU is used as a signal to adjust the size of the
75 // young generation.
76 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
77 FLAG_SET_DEFAULT(GCPauseIntervalMillis, 5000);
78 }
79
80 // Set up default number of concurrent threads. We want to have cycles complete fast
81 // enough, but we also do not want to steal too much CPU from the concurrently running
82 // application. Using 1/4 of available threads for concurrent GC seems a good
83 // compromise here.
84 bool ergo_conc = FLAG_IS_DEFAULT(ConcGCThreads);
85 if (ergo_conc) {
86 FLAG_SET_DEFAULT(ConcGCThreads, MAX2(1, os::initial_active_processor_count() / 4));
87 }
88
89 if (ConcGCThreads == 0) {
90 vm_exit_during_initialization("Shenandoah expects ConcGCThreads > 0, check -XX:ConcGCThreads=#");
91 }
92
93 // Set up default number of parallel threads. We want to have decent pauses performance
94 // which would use parallel threads, but we also do not want to do too many threads
95 // that will overwhelm the OS scheduler. Using 1/2 of available threads seems to be a fair
96 // compromise here. Due to implementation constraints, it should not be lower than
97 // the number of concurrent threads.
98 bool ergo_parallel = FLAG_IS_DEFAULT(ParallelGCThreads);
99 if (ergo_parallel) {
100 FLAG_SET_DEFAULT(ParallelGCThreads, MAX2(1, os::initial_active_processor_count() / 2));
101 }
102
103 if (ParallelGCThreads == 0) {
104 vm_exit_during_initialization("Shenandoah expects ParallelGCThreads > 0, check -XX:ParallelGCThreads=#");
105 }
106
107 // Make sure ergonomic decisions do not break the thread count invariants.
108 // This may happen when user overrides one of the flags, but not the other.
109 // When that happens, we want to adjust the setting that was set ergonomically.
110 if (ParallelGCThreads < ConcGCThreads) {
111 if (ergo_conc && !ergo_parallel) {
112 FLAG_SET_DEFAULT(ConcGCThreads, ParallelGCThreads);
113 } else if (!ergo_conc && ergo_parallel) {
114 FLAG_SET_DEFAULT(ParallelGCThreads, ConcGCThreads);
115 } else if (ergo_conc && ergo_parallel) {
116 // Should not happen, check the ergonomic computation above. Fail with relevant error.
117 vm_exit_during_initialization("Shenandoah thread count ergonomic error");
118 } else {
119 // User settings error, report and ask user to rectify.
120 vm_exit_during_initialization("Shenandoah expects ConcGCThreads <= ParallelGCThreads, check -XX:ParallelGCThreads, -XX:ConcGCThreads");
121 }
122 }
123
124 if (ShenandoahRegionSampling && FLAG_IS_DEFAULT(PerfDataMemorySize)) {
125 // When sampling is enabled, max out the PerfData memory to get more
126 // Shenandoah data in, including Matrix.
127 FLAG_SET_DEFAULT(PerfDataMemorySize, 2048*K);
128 }
129
130 #ifdef COMPILER2
131 // Shenandoah cares more about pause times, rather than raw throughput.
132 if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) {
133 FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true);
134 if (FLAG_IS_DEFAULT(LoopStripMiningIter)) {
135 FLAG_SET_DEFAULT(LoopStripMiningIter, 1000);
136 }
137 }
138 #ifdef ASSERT
139 // C2 barrier verification is only reliable when all default barriers are enabled
140 if (ShenandoahVerifyOptoBarriers &&
141 (!FLAG_IS_DEFAULT(ShenandoahSATBBarrier) ||
142 !FLAG_IS_DEFAULT(ShenandoahLoadRefBarrier) ||
143 !FLAG_IS_DEFAULT(ShenandoahIUBarrier) ||
144 !FLAG_IS_DEFAULT(ShenandoahCASBarrier) ||
145 !FLAG_IS_DEFAULT(ShenandoahCloneBarrier)
146 )) {
147 warning("Unusual barrier configuration, disabling C2 barrier verification");
148 FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
149 }
150 #else
151 guarantee(!ShenandoahVerifyOptoBarriers, "Should be disabled");
152 #endif // ASSERT
153 #endif // COMPILER2
154
155 // Record more information about previous cycles for improved debugging pleasure
156 if (FLAG_IS_DEFAULT(LogEventsBufferEntries)) {
157 FLAG_SET_DEFAULT(LogEventsBufferEntries, 250);
158 }
159
160 if ((InitialHeapSize == MaxHeapSize) && ShenandoahUncommit) {
161 log_info(gc)("Min heap equals to max heap, disabling ShenandoahUncommit");
162 FLAG_SET_DEFAULT(ShenandoahUncommit, false);
163 }
164
165 // If class unloading is disabled, no unloading for concurrent cycles as well.
166 if (!ClassUnloading) {
167 FLAG_SET_DEFAULT(ClassUnloadingWithConcurrentMark, false);
168 }
169
170 // TLAB sizing policy makes resizing decisions before each GC cycle. It averages
171 // historical data, assigning more recent data the weight according to TLABAllocationWeight.
172 // Current default is good for generational collectors that run frequent young GCs.
173 // With Shenandoah, GC cycles are much less frequent, so we need we need sizing policy
174 // to converge faster over smaller number of resizing decisions.
175 if (FLAG_IS_DEFAULT(TLABAllocationWeight)) {
176 FLAG_SET_DEFAULT(TLABAllocationWeight, 90);
177 }
178 }
179
180 size_t ShenandoahArguments::conservative_max_heap_alignment() {
181 size_t align = ShenandoahMaxRegionSize;
182 if (UseLargePages) {
183 align = MAX2(align, os::large_page_size());
184 }
185 return align;
186 }
187
188 void ShenandoahArguments::initialize_alignments() {
189 CardTable::initialize_card_size();
190
191 // Need to setup sizes early to get correct alignments.
192 MaxHeapSize = ShenandoahHeapRegion::setup_sizes(MaxHeapSize);
193
194 // This is expected by our algorithm for ShenandoahHeap::heap_region_containing().
195 size_t align = ShenandoahHeapRegion::region_size_bytes();
196 if (UseLargePages) {
197 align = MAX2(align, os::large_page_size());
198 }
199 SpaceAlignment = align;
200 HeapAlignment = align;
201 }
202
203 CollectedHeap* ShenandoahArguments::create_heap() {
204 return new ShenandoahHeap(new ShenandoahCollectorPolicy());
205 }