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 }