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