1 /* 2 * Copyright (c) 2018, 2020, 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/gcCause.hpp" 28 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp" 29 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp" 30 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp" 31 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp" 32 #include "logging/log.hpp" 33 #include "logging/logTag.hpp" 34 #include "runtime/globals_extension.hpp" 35 #include "utilities/quickSort.hpp" 36 37 // sort by decreasing garbage (so most garbage comes first) 38 int ShenandoahHeuristics::compare_by_garbage(RegionData a, RegionData b) { 39 if (a._u._garbage > b._u._garbage) 40 return -1; 41 else if (a._u._garbage < b._u._garbage) 42 return 1; 43 else return 0; 44 } 45 46 ShenandoahHeuristics::ShenandoahHeuristics(ShenandoahSpaceInfo* space_info) : 47 _space_info(space_info), 48 _region_data(nullptr), 49 _guaranteed_gc_interval(0), 50 _cycle_start(os::elapsedTime()), 51 _last_cycle_end(0), 52 _gc_times_learned(0), 53 _gc_time_penalties(0), 54 _gc_cycle_time_history(new TruncatedSeq(Moving_Average_Samples, ShenandoahAdaptiveDecayFactor)), 55 _metaspace_oom() 56 { 57 // No unloading during concurrent mark? Communicate that to heuristics 58 if (!ClassUnloadingWithConcurrentMark) { 59 FLAG_SET_DEFAULT(ShenandoahUnloadClassesFrequency, 0); 60 } 61 62 size_t num_regions = ShenandoahHeap::heap()->num_regions(); 63 assert(num_regions > 0, "Sanity"); 64 65 _region_data = NEW_C_HEAP_ARRAY(RegionData, num_regions, mtGC); 66 } 67 68 ShenandoahHeuristics::~ShenandoahHeuristics() { 69 FREE_C_HEAP_ARRAY(RegionGarbage, _region_data); 70 } 71 72 void ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set) { 73 assert(collection_set->is_empty(), "Must be empty"); 74 75 ShenandoahHeap* heap = ShenandoahHeap::heap(); 76 77 // Check all pinned regions have updated status before choosing the collection set. 78 heap->assert_pinned_region_status(); 79 80 // Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away. 81 82 size_t num_regions = heap->num_regions(); 83 84 RegionData* candidates = _region_data; 85 86 size_t cand_idx = 0; 87 88 size_t total_garbage = 0; 89 90 size_t immediate_garbage = 0; 91 size_t immediate_regions = 0; 92 93 size_t free = 0; 94 size_t free_regions = 0; 95 96 ShenandoahMarkingContext* const ctx = heap->complete_marking_context(); 97 98 for (size_t i = 0; i < num_regions; i++) { 99 ShenandoahHeapRegion* region = heap->get_region(i); 100 101 size_t garbage = region->garbage(); 102 total_garbage += garbage; 103 104 if (region->is_empty()) { 105 free_regions++; 106 free += ShenandoahHeapRegion::region_size_bytes(); 107 } else if (region->is_regular()) { 108 if (!region->has_live()) { 109 // We can recycle it right away and put it in the free set. 110 immediate_regions++; 111 immediate_garbage += garbage; 112 region->make_trash_immediate(); 113 } else { 114 // This is our candidate for later consideration. 115 candidates[cand_idx]._region = region; 116 candidates[cand_idx]._u._garbage = garbage; 117 cand_idx++; 118 } 119 } else if (region->is_humongous_start()) { 120 // Reclaim humongous regions here, and count them as the immediate garbage 121 #ifdef ASSERT 122 bool reg_live = region->has_live(); 123 bool bm_live = ctx->is_marked(cast_to_oop(region->bottom())); 124 assert(reg_live == bm_live, 125 "Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: " SIZE_FORMAT, 126 BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words()); 127 #endif 128 if (!region->has_live()) { 129 heap->trash_humongous_region_at(region); 130 131 // Count only the start. Continuations would be counted on "trash" path 132 immediate_regions++; 133 immediate_garbage += garbage; 134 } 135 } else if (region->is_trash()) { 136 // Count in just trashed collection set, during coalesced CM-with-UR 137 immediate_regions++; 138 immediate_garbage += garbage; 139 } 140 } 141 142 // Step 2. Look back at garbage statistics, and decide if we want to collect anything, 143 // given the amount of immediately reclaimable garbage. If we do, figure out the collection set. 144 145 assert (immediate_garbage <= total_garbage, 146 "Cannot have more immediate garbage than total garbage: " SIZE_FORMAT "%s vs " SIZE_FORMAT "%s", 147 byte_size_in_proper_unit(immediate_garbage), proper_unit_for_byte_size(immediate_garbage), 148 byte_size_in_proper_unit(total_garbage), proper_unit_for_byte_size(total_garbage)); 149 150 size_t immediate_percent = (total_garbage == 0) ? 0 : (immediate_garbage * 100 / total_garbage); 151 152 if (immediate_percent <= ShenandoahImmediateThreshold) { 153 choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free); 154 } 155 156 size_t cset_percent = (total_garbage == 0) ? 0 : (collection_set->garbage() * 100 / total_garbage); 157 size_t collectable_garbage = collection_set->garbage() + immediate_garbage; 158 size_t collectable_garbage_percent = (total_garbage == 0) ? 0 : (collectable_garbage * 100 / total_garbage); 159 160 log_info(gc, ergo)("Collectable Garbage: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), " 161 "Immediate: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), " SIZE_FORMAT " regions, " 162 "CSet: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), " SIZE_FORMAT " regions", 163 164 byte_size_in_proper_unit(collectable_garbage), 165 proper_unit_for_byte_size(collectable_garbage), 166 collectable_garbage_percent, 167 168 byte_size_in_proper_unit(immediate_garbage), 169 proper_unit_for_byte_size(immediate_garbage), 170 immediate_percent, 171 immediate_regions, 172 173 byte_size_in_proper_unit(collection_set->garbage()), 174 proper_unit_for_byte_size(collection_set->garbage()), 175 cset_percent, 176 collection_set->count()); 177 } 178 179 void ShenandoahHeuristics::record_cycle_start() { 180 _cycle_start = os::elapsedTime(); 181 } 182 183 void ShenandoahHeuristics::record_cycle_end() { 184 _last_cycle_end = os::elapsedTime(); 185 } 186 187 bool ShenandoahHeuristics::should_start_gc() { 188 // Perform GC to cleanup metaspace 189 if (has_metaspace_oom()) { 190 // Some of vmTestbase/metaspace tests depend on following line to count GC cycles 191 log_info(gc)("Trigger: %s", GCCause::to_string(GCCause::_metadata_GC_threshold)); 192 return true; 193 } 194 195 if (_guaranteed_gc_interval > 0) { 196 double last_time_ms = (os::elapsedTime() - _last_cycle_end) * 1000; 197 if (last_time_ms > _guaranteed_gc_interval) { 198 log_info(gc)("Trigger (%s): Time since last GC (%.0f ms) is larger than guaranteed interval (" UINTX_FORMAT " ms)", 199 _space_info->name(), last_time_ms, _guaranteed_gc_interval); 200 return true; 201 } 202 } 203 204 return false; 205 } 206 207 bool ShenandoahHeuristics::should_degenerate_cycle() { 208 return ShenandoahHeap::heap()->shenandoah_policy()->consecutive_degenerated_gc_count() <= ShenandoahFullGCThreshold; 209 } 210 211 void ShenandoahHeuristics::adjust_penalty(intx step) { 212 assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100, 213 "In range before adjustment: " INTX_FORMAT, _gc_time_penalties); 214 215 intx new_val = _gc_time_penalties + step; 216 if (new_val < 0) { 217 new_val = 0; 218 } 219 if (new_val > 100) { 220 new_val = 100; 221 } 222 _gc_time_penalties = new_val; 223 224 assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100, 225 "In range after adjustment: " INTX_FORMAT, _gc_time_penalties); 226 } 227 228 void ShenandoahHeuristics::record_success_concurrent(bool abbreviated) { 229 _gc_times_learned++; 230 231 adjust_penalty(Concurrent_Adjust); 232 233 if (_gc_times_learned <= ShenandoahLearningSteps || !(abbreviated && ShenandoahAdaptiveIgnoreShortCycles)) { 234 _gc_cycle_time_history->add(elapsed_cycle_time()); 235 } 236 } 237 238 void ShenandoahHeuristics::record_success_degenerated() { 239 adjust_penalty(Degenerated_Penalty); 240 } 241 242 void ShenandoahHeuristics::record_success_full() { 243 adjust_penalty(Full_Penalty); 244 } 245 246 void ShenandoahHeuristics::record_allocation_failure_gc() { 247 // Do nothing. 248 } 249 250 void ShenandoahHeuristics::record_requested_gc() { 251 // Assume users call System.gc() when external state changes significantly, 252 // which forces us to re-learn the GC timings and allocation rates. 253 _gc_times_learned = 0; 254 } 255 256 bool ShenandoahHeuristics::can_unload_classes() { 257 if (!ClassUnloading) return false; 258 return true; 259 } 260 261 bool ShenandoahHeuristics::can_unload_classes_normal() { 262 if (!can_unload_classes()) return false; 263 if (has_metaspace_oom()) return true; 264 if (!ClassUnloadingWithConcurrentMark) return false; 265 if (ShenandoahUnloadClassesFrequency == 0) return false; 266 return true; 267 } 268 269 bool ShenandoahHeuristics::should_unload_classes() { 270 if (!can_unload_classes_normal()) return false; 271 if (has_metaspace_oom()) return true; 272 size_t cycle = ShenandoahHeap::heap()->shenandoah_policy()->cycle_counter(); 273 // Unload classes every Nth GC cycle. 274 // This should not happen in the same cycle as process_references to amortize costs. 275 // Offsetting by one is enough to break the rendezvous when periods are equal. 276 // When periods are not equal, offsetting by one is just as good as any other guess. 277 return (cycle + 1) % ShenandoahUnloadClassesFrequency == 0; 278 } 279 280 void ShenandoahHeuristics::initialize() { 281 // Nothing to do by default. 282 } 283 284 double ShenandoahHeuristics::elapsed_cycle_time() const { 285 return os::elapsedTime() - _cycle_start; 286 }