2
* Copyright (c) 2018, 2022, Red Hat, Inc. All rights reserved.
3
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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.
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).
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.
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
25
#include "precompiled.hpp"
26
#include "gc/shared/gcArguments.hpp"
27
#include "gc/shared/tlab_globals.hpp"
28
#include "gc/shared/workerPolicy.hpp"
29
#include "gc/shenandoah/shenandoahArguments.hpp"
30
#include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
31
#include "gc/shenandoah/shenandoahHeap.inline.hpp"
32
#include "gc/shenandoah/shenandoahHeapRegion.hpp"
33
#include "runtime/globals_extension.hpp"
34
#include "runtime/java.hpp"
35
#include "utilities/defaultStream.hpp"
37
void ShenandoahArguments::initialize() {
38
#if !(defined AARCH64 || defined AMD64 || defined IA32 || defined PPC64 || defined RISCV64)
39
vm_exit_during_initialization("Shenandoah GC is not supported on this platform.");
42
#if 0 // leave this block as stepping stone for future platforms
43
log_warning(gc)("Shenandoah GC is not fully supported on this platform:");
44
log_warning(gc)(" concurrent modes are not supported, only STW cycles are enabled;");
45
log_warning(gc)(" arch-specific barrier code is not implemented, disabling barriers;");
47
FLAG_SET_DEFAULT(ShenandoahGCHeuristics, "passive");
49
FLAG_SET_DEFAULT(ShenandoahSATBBarrier, false);
50
FLAG_SET_DEFAULT(ShenandoahLoadRefBarrier, false);
51
FLAG_SET_DEFAULT(ShenandoahCASBarrier, false);
52
FLAG_SET_DEFAULT(ShenandoahCloneBarrier, false);
54
FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
57
size_t large_page_size = os::large_page_size();
58
if ((align_up(MaxHeapSize, large_page_size) / large_page_size) < ShenandoahHeapRegion::MIN_NUM_REGIONS) {
59
warning("Large pages size (" SIZE_FORMAT "K) is too large to afford page-sized regions, disabling uncommit",
60
os::large_page_size() / K);
61
FLAG_SET_DEFAULT(ShenandoahUncommit, false);
65
// Enable NUMA by default. While Shenandoah is not NUMA-aware, enabling NUMA makes
66
// storage allocation code NUMA-aware.
67
if (FLAG_IS_DEFAULT(UseNUMA)) {
68
FLAG_SET_DEFAULT(UseNUMA, true);
71
// Set up default number of concurrent threads. We want to have cycles complete fast
72
// enough, but we also do not want to steal too much CPU from the concurrently running
73
// application. Using 1/4 of available threads for concurrent GC seems a good
75
bool ergo_conc = FLAG_IS_DEFAULT(ConcGCThreads);
77
FLAG_SET_DEFAULT(ConcGCThreads, MAX2(1, os::initial_active_processor_count() / 4));
80
if (ConcGCThreads == 0) {
81
vm_exit_during_initialization("Shenandoah expects ConcGCThreads > 0, check -XX:ConcGCThreads=#");
84
// Set up default number of parallel threads. We want to have decent pauses performance
85
// which would use parallel threads, but we also do not want to do too many threads
86
// that will overwhelm the OS scheduler. Using 1/2 of available threads seems to be a fair
87
// compromise here. Due to implementation constraints, it should not be lower than
88
// the number of concurrent threads.
89
bool ergo_parallel = FLAG_IS_DEFAULT(ParallelGCThreads);
91
FLAG_SET_DEFAULT(ParallelGCThreads, MAX2(1, os::initial_active_processor_count() / 2));
94
if (ParallelGCThreads == 0) {
95
vm_exit_during_initialization("Shenandoah expects ParallelGCThreads > 0, check -XX:ParallelGCThreads=#");
98
// Make sure ergonomic decisions do not break the thread count invariants.
99
// This may happen when user overrides one of the flags, but not the other.
100
// When that happens, we want to adjust the setting that was set ergonomically.
101
if (ParallelGCThreads < ConcGCThreads) {
102
if (ergo_conc && !ergo_parallel) {
103
FLAG_SET_DEFAULT(ConcGCThreads, ParallelGCThreads);
104
} else if (!ergo_conc && ergo_parallel) {
105
FLAG_SET_DEFAULT(ParallelGCThreads, ConcGCThreads);
106
} else if (ergo_conc && ergo_parallel) {
107
// Should not happen, check the ergonomic computation above. Fail with relevant error.
108
vm_exit_during_initialization("Shenandoah thread count ergonomic error");
110
// User settings error, report and ask user to rectify.
111
vm_exit_during_initialization("Shenandoah expects ConcGCThreads <= ParallelGCThreads, check -XX:ParallelGCThreads, -XX:ConcGCThreads");
115
// Disable support for dynamic number of GC threads. We do not let the runtime
116
// heuristics to misjudge how many threads we need during the heavy concurrent phase
118
if (UseDynamicNumberOfGCThreads) {
119
if (FLAG_IS_CMDLINE(UseDynamicNumberOfGCThreads)) {
120
warning("Shenandoah does not support UseDynamicNumberOfGCThreads, disabling");
122
FLAG_SET_DEFAULT(UseDynamicNumberOfGCThreads, false);
125
if (ShenandoahRegionSampling && FLAG_IS_DEFAULT(PerfDataMemorySize)) {
126
// When sampling is enabled, max out the PerfData memory to get more
127
// Shenandoah data in, including Matrix.
128
FLAG_SET_DEFAULT(PerfDataMemorySize, 2048*K);
132
// Shenandoah cares more about pause times, rather than raw throughput.
133
if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) {
134
FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true);
135
if (FLAG_IS_DEFAULT(LoopStripMiningIter)) {
136
FLAG_SET_DEFAULT(LoopStripMiningIter, 1000);
140
// C2 barrier verification is only reliable when all default barriers are enabled
141
if (ShenandoahVerifyOptoBarriers &&
142
(!FLAG_IS_DEFAULT(ShenandoahSATBBarrier) ||
143
!FLAG_IS_DEFAULT(ShenandoahLoadRefBarrier) ||
144
!FLAG_IS_DEFAULT(ShenandoahCASBarrier) ||
145
!FLAG_IS_DEFAULT(ShenandoahCloneBarrier)
147
warning("Unusual barrier configuration, disabling C2 barrier verification");
148
FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false);
151
guarantee(!ShenandoahVerifyOptoBarriers, "Should be disabled");
155
// Record more information about previous cycles for improved debugging pleasure
156
if (FLAG_IS_DEFAULT(LogEventsBufferEntries)) {
157
FLAG_SET_DEFAULT(LogEventsBufferEntries, 250);
160
if ((InitialHeapSize == MaxHeapSize) && ShenandoahUncommit) {
161
log_info(gc)("Min heap equals to max heap, disabling ShenandoahUncommit");
162
FLAG_SET_DEFAULT(ShenandoahUncommit, false);
165
// If class unloading is disabled, no unloading for concurrent cycles as well.
166
if (!ClassUnloading) {
167
FLAG_SET_DEFAULT(ClassUnloadingWithConcurrentMark, false);
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);
180
size_t ShenandoahArguments::conservative_max_heap_alignment() {
181
size_t align = ShenandoahMaxRegionSize;
183
align = MAX2(align, os::large_page_size());
188
void ShenandoahArguments::initialize_alignments() {
189
// Need to setup sizes early to get correct alignments.
190
MaxHeapSize = ShenandoahHeapRegion::setup_sizes(MaxHeapSize);
192
// This is expected by our algorithm for ShenandoahHeap::heap_region_containing().
193
size_t align = ShenandoahHeapRegion::region_size_bytes();
195
align = MAX2(align, os::large_page_size());
197
SpaceAlignment = align;
198
HeapAlignment = align;
201
CollectedHeap* ShenandoahArguments::create_heap() {
202
return new ShenandoahHeap(new ShenandoahCollectorPolicy());