1 /* 2 * Copyright (c) 2017, Red Hat, Inc. and/or its affiliates. 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/cms/cmsArguments.hpp" 27 #include "gc/cms/cmsCollectorPolicy.hpp" 28 #include "gc/cms/cmsHeap.hpp" 29 #include "gc/cms/compactibleFreeListSpace.hpp" 30 #include "gc/shared/gcArguments.inline.hpp" 31 #include "gc/shared/genCollectedHeap.hpp" 32 #include "runtime/arguments.hpp" 33 #include "runtime/globals.hpp" 34 #include "runtime/globals_extension.hpp" 35 #include "runtime/vm_version.hpp" 36 #include "utilities/defaultStream.hpp" 37 38 size_t CMSArguments::conservative_max_heap_alignment() { 39 return GenCollectedHeap::conservative_max_heap_alignment(); 40 } 41 42 void CMSArguments::set_parnew_gc_flags() { 43 assert(!UseSerialGC && !UseParallelOldGC && !UseParallelGC && !UseG1GC, 44 "control point invariant"); 45 assert(UseConcMarkSweepGC, "CMS is expected to be on here"); 46 47 if (FLAG_IS_DEFAULT(ParallelGCThreads)) { 48 FLAG_SET_DEFAULT(ParallelGCThreads, Abstract_VM_Version::parallel_worker_threads()); 49 assert(ParallelGCThreads > 0, "We should always have at least one thread by default"); 50 } else if (ParallelGCThreads == 0) { 51 jio_fprintf(defaultStream::error_stream(), 52 "The ParNew GC can not be combined with -XX:ParallelGCThreads=0\n"); 53 vm_exit(1); 54 } 55 56 // By default YoungPLABSize and OldPLABSize are set to 4096 and 1024 respectively, 57 // these settings are default for Parallel Scavenger. For ParNew+Tenured configuration 58 // we set them to 1024 and 1024. 59 // See CR 6362902. 60 if (FLAG_IS_DEFAULT(YoungPLABSize)) { 61 FLAG_SET_DEFAULT(YoungPLABSize, (intx)1024); 62 } 63 if (FLAG_IS_DEFAULT(OldPLABSize)) { 64 FLAG_SET_DEFAULT(OldPLABSize, (intx)1024); 65 } 66 67 // When using compressed oops, we use local overflow stacks, 68 // rather than using a global overflow list chained through 69 // the klass word of the object's pre-image. 70 if (UseCompressedOops && !ParGCUseLocalOverflow) { 71 if (!FLAG_IS_DEFAULT(ParGCUseLocalOverflow)) { 72 warning("Forcing +ParGCUseLocalOverflow: needed if using compressed references"); 73 } 74 FLAG_SET_DEFAULT(ParGCUseLocalOverflow, true); 75 } 76 assert(ParGCUseLocalOverflow || !UseCompressedOops, "Error"); 77 } 78 79 // Adjust some sizes to suit CMS and/or ParNew needs; these work well on 80 // sparc/solaris for certain applications, but would gain from 81 // further optimization and tuning efforts, and would almost 82 // certainly gain from analysis of platform and environment. 83 void CMSArguments::initialize() { 84 GCArguments::initialize(); 85 86 assert(!UseSerialGC && !UseParallelOldGC && !UseParallelGC, "Error"); 87 assert(UseConcMarkSweepGC, "CMS is expected to be on here"); 88 89 // CMS space iteration, which FLSVerifyAllHeapreferences entails, 90 // insists that we hold the requisite locks so that the iteration is 91 // MT-safe. For the verification at start-up and shut-down, we don't 92 // yet have a good way of acquiring and releasing these locks, 93 // which are not visible at the CollectedHeap level. We want to 94 // be able to acquire these locks and then do the iteration rather 95 // than just disable the lock verification. This will be fixed under 96 // bug 4788986. 97 if (UseConcMarkSweepGC && FLSVerifyAllHeapReferences) { 98 if (VerifyDuringStartup) { 99 warning("Heap verification at start-up disabled " 100 "(due to current incompatibility with FLSVerifyAllHeapReferences)"); 101 VerifyDuringStartup = false; // Disable verification at start-up 102 } 103 104 if (VerifyBeforeExit) { 105 warning("Heap verification at shutdown disabled " 106 "(due to current incompatibility with FLSVerifyAllHeapReferences)"); 107 VerifyBeforeExit = false; // Disable verification at shutdown 108 } 109 } 110 111 if (!ClassUnloading) { 112 FLAG_SET_CMDLINE(bool, CMSClassUnloadingEnabled, false); 113 } 114 115 // Set CMS global values 116 CompactibleFreeListSpace::set_cms_values(); 117 118 // Turn off AdaptiveSizePolicy by default for cms until it is complete. 119 disable_adaptive_size_policy("UseConcMarkSweepGC"); 120 121 set_parnew_gc_flags(); 122 123 size_t max_heap = align_down(MaxHeapSize, 124 CardTableRS::ct_max_alignment_constraint()); 125 126 // Now make adjustments for CMS 127 intx tenuring_default = (intx)6; 128 size_t young_gen_per_worker = CMSYoungGenPerWorker; 129 130 // Preferred young gen size for "short" pauses: 131 // upper bound depends on # of threads and NewRatio. 132 const size_t preferred_max_new_size_unaligned = 133 MIN2(max_heap/(NewRatio+1), ScaleForWordSize(young_gen_per_worker * ParallelGCThreads)); 134 size_t preferred_max_new_size = 135 align_up(preferred_max_new_size_unaligned, os::vm_page_size()); 136 137 // Unless explicitly requested otherwise, size young gen 138 // for "short" pauses ~ CMSYoungGenPerWorker*ParallelGCThreads 139 140 // If either MaxNewSize or NewRatio is set on the command line, 141 // assume the user is trying to set the size of the young gen. 142 if (FLAG_IS_DEFAULT(MaxNewSize) && FLAG_IS_DEFAULT(NewRatio)) { 143 144 // Set MaxNewSize to our calculated preferred_max_new_size unless 145 // NewSize was set on the command line and it is larger than 146 // preferred_max_new_size. 147 if (!FLAG_IS_DEFAULT(NewSize)) { // NewSize explicitly set at command-line 148 FLAG_SET_ERGO(size_t, MaxNewSize, MAX2(NewSize, preferred_max_new_size)); 149 } else { 150 FLAG_SET_ERGO(size_t, MaxNewSize, preferred_max_new_size); 151 } 152 log_trace(gc, heap)("CMS ergo set MaxNewSize: " SIZE_FORMAT, MaxNewSize); 153 154 // Code along this path potentially sets NewSize and OldSize 155 log_trace(gc, heap)("CMS set min_heap_size: " SIZE_FORMAT " initial_heap_size: " SIZE_FORMAT " max_heap: " SIZE_FORMAT, 156 Arguments::min_heap_size(), InitialHeapSize, max_heap); 157 size_t min_new = preferred_max_new_size; 158 if (FLAG_IS_CMDLINE(NewSize)) { 159 min_new = NewSize; 160 } 161 if (max_heap > min_new && Arguments::min_heap_size() > min_new) { 162 // Unless explicitly requested otherwise, make young gen 163 // at least min_new, and at most preferred_max_new_size. 164 if (FLAG_IS_DEFAULT(NewSize)) { 165 FLAG_SET_ERGO(size_t, NewSize, MAX2(NewSize, min_new)); 166 FLAG_SET_ERGO(size_t, NewSize, MIN2(preferred_max_new_size, NewSize)); 167 log_trace(gc, heap)("CMS ergo set NewSize: " SIZE_FORMAT, NewSize); 168 } 169 // Unless explicitly requested otherwise, size old gen 170 // so it's NewRatio x of NewSize. 171 if (FLAG_IS_DEFAULT(OldSize)) { 172 if (max_heap > NewSize) { 173 FLAG_SET_ERGO(size_t, OldSize, MIN2(NewRatio*NewSize, max_heap - NewSize)); 174 log_trace(gc, heap)("CMS ergo set OldSize: " SIZE_FORMAT, OldSize); 175 } 176 } 177 } 178 } 179 // Unless explicitly requested otherwise, definitely 180 // promote all objects surviving "tenuring_default" scavenges. 181 if (FLAG_IS_DEFAULT(MaxTenuringThreshold) && 182 FLAG_IS_DEFAULT(SurvivorRatio)) { 183 FLAG_SET_ERGO(uintx, MaxTenuringThreshold, tenuring_default); 184 } 185 // If we decided above (or user explicitly requested) 186 // `promote all' (via MaxTenuringThreshold := 0), 187 // prefer minuscule survivor spaces so as not to waste 188 // space for (non-existent) survivors 189 if (FLAG_IS_DEFAULT(SurvivorRatio) && MaxTenuringThreshold == 0) { 190 FLAG_SET_ERGO(uintx, SurvivorRatio, MAX2((uintx)1024, SurvivorRatio)); 191 } 192 193 // OldPLABSize is interpreted in CMS as not the size of the PLAB in words, 194 // but rather the number of free blocks of a given size that are used when 195 // replenishing the local per-worker free list caches. 196 if (FLAG_IS_DEFAULT(OldPLABSize)) { 197 if (!FLAG_IS_DEFAULT(ResizeOldPLAB) && !ResizeOldPLAB) { 198 // OldPLAB sizing manually turned off: Use a larger default setting, 199 // unless it was manually specified. This is because a too-low value 200 // will slow down scavenges. 201 FLAG_SET_ERGO(size_t, OldPLABSize, CompactibleFreeListSpaceLAB::_default_static_old_plab_size); // default value before 6631166 202 } else { 203 FLAG_SET_DEFAULT(OldPLABSize, CompactibleFreeListSpaceLAB::_default_dynamic_old_plab_size); // old CMSParPromoteBlocksToClaim default 204 } 205 } 206 207 // If either of the static initialization defaults have changed, note this 208 // modification. 209 if (!FLAG_IS_DEFAULT(OldPLABSize) || !FLAG_IS_DEFAULT(OldPLABWeight)) { 210 CompactibleFreeListSpaceLAB::modify_initialization(OldPLABSize, OldPLABWeight); 211 } 212 213 log_trace(gc)("MarkStackSize: %uk MarkStackSizeMax: %uk", (unsigned int) (MarkStackSize / K), (uint) (MarkStackSizeMax / K)); 214 } 215 216 void CMSArguments::disable_adaptive_size_policy(const char* collector_name) { 217 if (UseAdaptiveSizePolicy) { 218 if (FLAG_IS_CMDLINE(UseAdaptiveSizePolicy)) { 219 warning("Disabling UseAdaptiveSizePolicy; it is incompatible with %s.", 220 collector_name); 221 } 222 FLAG_SET_DEFAULT(UseAdaptiveSizePolicy, false); 223 } 224 } 225 226 CollectedHeap* CMSArguments::create_heap() { 227 return create_heap_with_policy<CMSHeap, ConcurrentMarkSweepPolicy>(); 228 }