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(ShenandoahStoreValEnqueueBarrier, false); 49 FLAG_SET_DEFAULT(ShenandoahCASBarrier, false); 50 FLAG_SET_DEFAULT(ShenandoahCloneBarrier, false); 51 52 FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false); 53 #endif 54 55 if (UseLargePages && (MaxHeapSize / os::large_page_size()) < ShenandoahHeapRegion::MIN_NUM_REGIONS) { 56 warning("Large pages size (" SIZE_FORMAT "K) is too large to afford page-sized regions, disabling uncommit", 57 os::large_page_size() / K); 58 FLAG_SET_DEFAULT(ShenandoahUncommit, false); 59 } 60 61 // Enable NUMA by default. While Shenandoah is not NUMA-aware, enabling NUMA makes 62 // storage allocation code NUMA-aware. 63 if (FLAG_IS_DEFAULT(UseNUMA)) { 64 FLAG_SET_DEFAULT(UseNUMA, true); 65 } 66 67 // Set up default number of concurrent threads. We want to have cycles complete fast 68 // enough, but we also do not want to steal too much CPU from the concurrently running 69 // application. Using 1/4 of available threads for concurrent GC seems a good 70 // compromise here. 71 bool ergo_conc = FLAG_IS_DEFAULT(ConcGCThreads); 72 if (ergo_conc) { 73 FLAG_SET_DEFAULT(ConcGCThreads, MAX2(1, os::initial_active_processor_count() / 4)); 74 } 75 76 if (ConcGCThreads == 0) { 77 vm_exit_during_initialization("Shenandoah expects ConcGCThreads > 0, check -XX:ConcGCThreads=#"); 78 } 79 80 // Set up default number of parallel threads. We want to have decent pauses performance 81 // which would use parallel threads, but we also do not want to do too many threads 82 // that will overwhelm the OS scheduler. Using 1/2 of available threads seems to be a fair 83 // compromise here. Due to implementation constraints, it should not be lower than 84 // the number of concurrent threads. 85 bool ergo_parallel = FLAG_IS_DEFAULT(ParallelGCThreads); 86 if (ergo_parallel) { 87 FLAG_SET_DEFAULT(ParallelGCThreads, MAX2(1, os::initial_active_processor_count() / 2)); 88 } 89 90 if (ParallelGCThreads == 0) { 91 vm_exit_during_initialization("Shenandoah expects ParallelGCThreads > 0, check -XX:ParallelGCThreads=#"); 92 } 93 94 // Make sure ergonomic decisions do not break the thread count invariants. 95 // This may happen when user overrides one of the flags, but not the other. 96 // When that happens, we want to adjust the setting that was set ergonomically. 97 if (ParallelGCThreads < ConcGCThreads) { 98 if (ergo_conc && !ergo_parallel) { 99 FLAG_SET_DEFAULT(ConcGCThreads, ParallelGCThreads); 100 } else if (!ergo_conc && ergo_parallel) { 101 FLAG_SET_DEFAULT(ParallelGCThreads, ConcGCThreads); 102 } else if (ergo_conc && ergo_parallel) { 103 // Should not happen, check the ergonomic computation above. Fail with relevant error. 104 vm_exit_during_initialization("Shenandoah thread count ergonomic error"); 105 } else { 106 // User settings error, report and ask user to rectify. 107 vm_exit_during_initialization("Shenandoah expects ConcGCThreads <= ParallelGCThreads, check -XX:ParallelGCThreads, -XX:ConcGCThreads"); 108 } 109 } 110 111 if (FLAG_IS_DEFAULT(ParallelRefProcEnabled)) { 112 FLAG_SET_DEFAULT(ParallelRefProcEnabled, true); 113 } 114 115 if (ShenandoahRegionSampling && FLAG_IS_DEFAULT(PerfDataMemorySize)) { 116 // When sampling is enabled, max out the PerfData memory to get more 117 // Shenandoah data in, including Matrix. 118 FLAG_SET_DEFAULT(PerfDataMemorySize, 2048*K); 119 } 120 121 #ifdef COMPILER2 122 // Shenandoah cares more about pause times, rather than raw throughput. 123 if (FLAG_IS_DEFAULT(UseCountedLoopSafepoints)) { 124 FLAG_SET_DEFAULT(UseCountedLoopSafepoints, true); 125 if (FLAG_IS_DEFAULT(LoopStripMiningIter)) { 126 FLAG_SET_DEFAULT(LoopStripMiningIter, 1000); 127 } 128 } 129 #ifdef ASSERT 130 // C2 barrier verification is only reliable when all default barriers are enabled 131 if (ShenandoahVerifyOptoBarriers && 132 (!FLAG_IS_DEFAULT(ShenandoahSATBBarrier) || 133 !FLAG_IS_DEFAULT(ShenandoahLoadRefBarrier) || 134 !FLAG_IS_DEFAULT(ShenandoahStoreValEnqueueBarrier) || 135 !FLAG_IS_DEFAULT(ShenandoahCASBarrier) || 136 !FLAG_IS_DEFAULT(ShenandoahCloneBarrier) 137 )) { 138 warning("Unusual barrier configuration, disabling C2 barrier verification"); 139 FLAG_SET_DEFAULT(ShenandoahVerifyOptoBarriers, false); 140 } 141 #else 142 guarantee(!ShenandoahVerifyOptoBarriers, "Should be disabled"); 143 #endif // ASSERT 144 #endif // COMPILER2 145 146 // Record more information about previous cycles for improved debugging pleasure 147 if (FLAG_IS_DEFAULT(LogEventsBufferEntries)) { 148 FLAG_SET_DEFAULT(LogEventsBufferEntries, 250); 149 } 150 151 if (AlwaysPreTouch) { 152 if (!FLAG_IS_DEFAULT(ShenandoahUncommit)) { 153 warning("AlwaysPreTouch is enabled, disabling ShenandoahUncommit"); 154 } 155 FLAG_SET_DEFAULT(ShenandoahUncommit, false); 156 } 157 158 if ((InitialHeapSize == MaxHeapSize) && ShenandoahUncommit) { 159 log_info(gc)("Min heap equals to max heap, disabling ShenandoahUncommit"); 160 FLAG_SET_DEFAULT(ShenandoahUncommit, false); 161 } 162 163 // If class unloading is disabled, no unloading for concurrent cycles as well. 164 if (!ClassUnloading) { 165 FLAG_SET_DEFAULT(ClassUnloadingWithConcurrentMark, false); 166 } 167 168 // AOT is not supported yet 169 if (UseAOT) { 170 if (!FLAG_IS_DEFAULT(UseAOT)) { 171 warning("Shenandoah does not support AOT at this moment, disabling UseAOT"); 172 } 173 FLAG_SET_DEFAULT(UseAOT, false); 174 } 175 176 // TLAB sizing policy makes resizing decisions before each GC cycle. It averages 177 // historical data, assigning more recent data the weight according to TLABAllocationWeight. 178 // Current default is good for generational collectors that run frequent young GCs. 179 // With Shenandoah, GC cycles are much less frequent, so we need we need sizing policy 180 // to converge faster over smaller number of resizing decisions. 181 if (FLAG_IS_DEFAULT(TLABAllocationWeight)) { 182 FLAG_SET_DEFAULT(TLABAllocationWeight, 90); 183 } 184 } 185 186 size_t ShenandoahArguments::conservative_max_heap_alignment() { 187 size_t align = ShenandoahMaxRegionSize; 188 if (UseLargePages) { 189 align = MAX2(align, os::large_page_size()); 190 } 191 return align; 192 } 193 194 void ShenandoahArguments::initialize_alignments() { 195 // Need to setup sizes early to get correct alignments. 196 ShenandoahHeapRegion::setup_sizes(MaxHeapSize); 197 198 // This is expected by our algorithm for ShenandoahHeap::heap_region_containing(). 199 size_t align = ShenandoahHeapRegion::region_size_bytes(); 200 if (UseLargePages) { 201 align = MAX2(align, os::large_page_size()); 202 } 203 SpaceAlignment = align; 204 HeapAlignment = align; 205 } 206 207 CollectedHeap* ShenandoahArguments::create_heap() { 208 return new ShenandoahHeap(new ShenandoahCollectorPolicy()); 209 }