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.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
34 void 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.
64 if (FLAG_IS_DEFAULT(UseNUMA)) {
65 FLAG_SET_DEFAULT(UseNUMA, true);
66 }
67
68 // Set up default number of concurrent threads. We want to have cycles complete fast
69 // enough, but we also do not want to steal too much CPU from the concurrently running
70 // application. Using 1/4 of available threads for concurrent GC seems a good
71 // compromise here.
72 bool ergo_conc = FLAG_IS_DEFAULT(ConcGCThreads);
73 if (ergo_conc) {
74 FLAG_SET_DEFAULT(ConcGCThreads, MAX2(1, os::initial_active_processor_count() / 4));
75 }
76
77 if (ConcGCThreads == 0) {
78 vm_exit_during_initialization("Shenandoah expects ConcGCThreads > 0, check -XX:ConcGCThreads=#");
79 }
80
81 // Set up default number of parallel threads. We want to have decent pauses performance
82 // which would use parallel threads, but we also do not want to do too many threads
83 // that will overwhelm the OS scheduler. Using 1/2 of available threads seems to be a fair
84 // compromise here. Due to implementation constraints, it should not be lower than
85 // the number of concurrent threads.
86 bool ergo_parallel = FLAG_IS_DEFAULT(ParallelGCThreads);
87 if (ergo_parallel) {
88 FLAG_SET_DEFAULT(ParallelGCThreads, MAX2(1, os::initial_active_processor_count() / 2));
89 }
90
91 if (ParallelGCThreads == 0) {
92 vm_exit_during_initialization("Shenandoah expects ParallelGCThreads > 0, check -XX:ParallelGCThreads=#");
93 }
94
95 // Make sure ergonomic decisions do not break the thread count invariants.
96 // This may happen when user overrides one of the flags, but not the other.
97 // When that happens, we want to adjust the setting that was set ergonomically.
98 if (ParallelGCThreads < ConcGCThreads) {
99 if (ergo_conc && !ergo_parallel) {
100 FLAG_SET_DEFAULT(ConcGCThreads, ParallelGCThreads);
101 } else if (!ergo_conc && ergo_parallel) {
102 FLAG_SET_DEFAULT(ParallelGCThreads, ConcGCThreads);
103 } else if (ergo_conc && ergo_parallel) {
104 // Should not happen, check the ergonomic computation above. Fail with relevant error.
105 vm_exit_during_initialization("Shenandoah thread count ergonomic error");
106 } else {
107 // User settings error, report and ask user to rectify.
108 vm_exit_during_initialization("Shenandoah expects ConcGCThreads <= ParallelGCThreads, check -XX:ParallelGCThreads, -XX:ConcGCThreads");
109 }
110 }
111
112 if (FLAG_IS_DEFAULT(ParallelRefProcEnabled)) {
113 FLAG_SET_DEFAULT(ParallelRefProcEnabled, true);
114 }
115
116 if (ShenandoahRegionSampling && FLAG_IS_DEFAULT(PerfDataMemorySize)) {
117 // When sampling is enabled, max out the PerfData memory to get more
118 // Shenandoah data in, including Matrix.
119 FLAG_SET_DEFAULT(PerfDataMemorySize, 2048*K);
120 }
121
122 #ifdef COMPILER2
123 // Shenandoah cares more about pause times, rather than raw throughput.
124 if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) {
125 FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true);
126 if (FLAG_IS_DEFAULT(LoopStripMiningIter)) {
127 FLAG_SET_DEFAULT(LoopStripMiningIter, 1000);
128 }
129 }
130 #ifdef ASSERT
131 // C2 barrier verification is only reliable when all default barriers are enabled
132 if (ShenandoahVerifyOptoBarriers &&
133 (!FLAG_IS_DEFAULT(ShenandoahSATBBarrier) ||
134 !FLAG_IS_DEFAULT(ShenandoahLoadRefBarrier) ||
135 !FLAG_IS_DEFAULT(ShenandoahKeepAliveBarrier) ||
136 !FLAG_IS_DEFAULT(ShenandoahStoreValEnqueueBarrier) ||
137 !FLAG_IS_DEFAULT(ShenandoahCASBarrier) ||
138 !FLAG_IS_DEFAULT(ShenandoahCloneBarrier)
139 )) {
140 warning("Unusual barrier configuration, disabling C2 barrier verification");
141 FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
142 }
143 #else
144 guarantee(!ShenandoahVerifyOptoBarriers, "Should be disabled");
145 #endif // ASSERT
146 #endif // COMPILER2
147
148 if (AlwaysPreTouch) {
149 // Shenandoah handles pre-touch on its own. It does not let the
150 // generic storage code to do the pre-touch before Shenandoah has
151 // a chance to do it on its own.
152 FLAG_SET_DEFAULT(AlwaysPreTouch, false);
153 FLAG_SET_DEFAULT(ShenandoahAlwaysPreTouch, true);
154 }
155
156 // Record more information about previous cycles for improved debugging pleasure
157 if (FLAG_IS_DEFAULT(LogEventsBufferEntries)) {
158 FLAG_SET_DEFAULT(LogEventsBufferEntries, 250);
159 }
160
161 if (ShenandoahAlwaysPreTouch) {
162 if (!FLAG_IS_DEFAULT(ShenandoahUncommit)) {
163 warning("AlwaysPreTouch is enabled, disabling ShenandoahUncommit");
164 }
165 FLAG_SET_DEFAULT(ShenandoahUncommit, false);
166 }
167
168 if ((InitialHeapSize == MaxHeapSize) && ShenandoahUncommit) {
169 log_info(gc)("Min heap equals to max heap, disabling ShenandoahUncommit");
170 FLAG_SET_DEFAULT(ShenandoahUncommit, false);
171 }
172
173 // If class unloading is disabled, no unloading for concurrent cycles as well.
174 if (!ClassUnloading) {
175 FLAG_SET_DEFAULT(ClassUnloadingWithConcurrentMark, false);
176 }
177
178 // AOT is not supported yet
179 if (UseAOT) {
180 if (!FLAG_IS_DEFAULT(UseAOT)) {
181 warning("Shenandoah does not support AOT at this moment, disabling UseAOT");
182 }
183 FLAG_SET_DEFAULT(UseAOT, false);
184 }
185
186 // TLAB sizing policy makes resizing decisions before each GC cycle. It averages
187 // historical data, assigning more recent data the weight according to TLABAllocationWeight.
188 // Current default is good for generational collectors that run frequent young GCs.
189 // With Shenandoah, GC cycles are much less frequent, so we need we need sizing policy
190 // to converge faster over smaller number of resizing decisions.
191 if (FLAG_IS_DEFAULT(TLABAllocationWeight)) {
192 FLAG_SET_DEFAULT(TLABAllocationWeight, 90);
193 }
194 }
195
196 size_t ShenandoahArguments::conservative_max_heap_alignment() {
197 size_t align = ShenandoahMaxRegionSize;
198 if (UseLargePages) {
199 align = MAX2(align, os::large_page_size());
200 }
201 return align;
202 }
203
204 void ShenandoahArguments::initialize_alignments() {
205 // Need to setup sizes early to get correct alignments.
206 ShenandoahHeapRegion::setup_sizes(MaxHeapSize);
207
208 // This is expected by our algorithm for ShenandoahHeap::heap_region_containing().
209 size_t align = ShenandoahHeapRegion::region_size_bytes();
210 if (UseLargePages) {
211 align = MAX2(align, os::large_page_size());
212 }
213 SpaceAlignment = align;
214 HeapAlignment = align;
215 }
216
217 CollectedHeap* ShenandoahArguments::create_heap() {
218 return new ShenandoahHeap(new ShenandoahCollectorPolicy());
219 }