1 /* 2 * Copyright (c) 2018, Red Hat, Inc. All rights reserved. 3 * 4 * This code is free software; you can redistribute it and/or modify it 5 * under the terms of the GNU General Public License version 2 only, as 6 * published by the Free Software Foundation. 7 * 8 * This code is distributed in the hope that it will be useful, but WITHOUT 9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 11 * version 2 for more details (a copy is included in the LICENSE file that 12 * accompanied this code). 13 * 14 * You should have received a copy of the GNU General Public License version 15 * 2 along with this work; if not, write to the Free Software Foundation, 16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 17 * 18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 19 * or visit www.oracle.com if you need additional information or have any 20 * questions. 21 * 22 */ 23 24 #include "precompiled.hpp" 25 26 #include "gc/shared/gcCause.hpp" 27 #include "gc/shenandoah/shenandoahBrooksPointer.hpp" 28 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp" 29 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp" 30 #include "gc/shenandoah/shenandoahHeap.inline.hpp" 31 #include "gc/shenandoah/shenandoahHeapRegion.hpp" 32 #include "gc/shenandoah/shenandoahHeuristics.hpp" 33 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp" 34 #include "logging/log.hpp" 35 #include "logging/logTag.hpp" 36 37 int ShenandoahHeuristics::compare_by_garbage(RegionData a, RegionData b) { 38 if (a._garbage > b._garbage) 39 return -1; 40 else if (a._garbage < b._garbage) 41 return 1; 42 else return 0; 43 } 44 45 int ShenandoahHeuristics::compare_by_garbage_then_alloc_seq_ascending(RegionData a, RegionData b) { 46 int r = compare_by_garbage(a, b); 47 if (r != 0) { 48 return r; 49 } 50 return compare_by_alloc_seq_ascending(a, b); 51 } 52 53 int ShenandoahHeuristics::compare_by_alloc_seq_ascending(RegionData a, RegionData b) { 54 if (a._seqnum_last_alloc == b._seqnum_last_alloc) 55 return 0; 56 else if (a._seqnum_last_alloc < b._seqnum_last_alloc) 57 return -1; 58 else return 1; 59 } 60 61 int ShenandoahHeuristics::compare_by_alloc_seq_descending(RegionData a, RegionData b) { 62 return -compare_by_alloc_seq_ascending(a, b); 63 } 64 65 ShenandoahHeuristics::ShenandoahHeuristics() : 66 _update_refs_early(false), 67 _update_refs_adaptive(false), 68 _region_data(NULL), 69 _region_data_size(0), 70 _degenerated_cycles_in_a_row(0), 71 _successful_cycles_in_a_row(0), 72 _bytes_in_cset(0), 73 _cycle_start(os::elapsedTime()), 74 _last_cycle_end(0), 75 _gc_times_learned(0), 76 _gc_time_penalties(0), 77 _gc_time_history(new TruncatedSeq(5)), 78 _metaspace_oom() 79 { 80 if (strcmp(ShenandoahUpdateRefsEarly, "on") == 0 || 81 strcmp(ShenandoahUpdateRefsEarly, "true") == 0 ) { 82 _update_refs_early = true; 83 } else if (strcmp(ShenandoahUpdateRefsEarly, "off") == 0 || 84 strcmp(ShenandoahUpdateRefsEarly, "false") == 0 ) { 85 _update_refs_early = false; 86 } else if (strcmp(ShenandoahUpdateRefsEarly, "adaptive") == 0) { 87 _update_refs_adaptive = true; 88 _update_refs_early = true; 89 } else { 90 vm_exit_during_initialization("Unknown -XX:ShenandoahUpdateRefsEarly option: %s", ShenandoahUpdateRefsEarly); 91 } 92 93 // No unloading during concurrent mark? Communicate that to heuristics 94 if (!ClassUnloadingWithConcurrentMark) { 95 FLAG_SET_DEFAULT(ShenandoahUnloadClassesFrequency, 0); 96 } 97 } 98 99 ShenandoahHeuristics::~ShenandoahHeuristics() { 100 if (_region_data != NULL) { 101 FREE_C_HEAP_ARRAY(RegionGarbage, _region_data); 102 } 103 } 104 105 ShenandoahHeuristics::RegionData* ShenandoahHeuristics::get_region_data_cache(size_t num) { 106 RegionData* res = _region_data; 107 if (res == NULL) { 108 res = NEW_C_HEAP_ARRAY(RegionData, num, mtGC); 109 _region_data = res; 110 _region_data_size = num; 111 } else if (_region_data_size < num) { 112 res = REALLOC_C_HEAP_ARRAY(RegionData, _region_data, num, mtGC); 113 _region_data = res; 114 _region_data_size = num; 115 } 116 return res; 117 } 118 119 void ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set) { 120 assert(collection_set->count() == 0, "Must be empty"); 121 122 ShenandoahHeap* heap = ShenandoahHeap::heap(); 123 124 // Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away. 125 126 size_t num_regions = heap->num_regions(); 127 128 RegionData* candidates = get_region_data_cache(num_regions); 129 130 size_t cand_idx = 0; 131 132 size_t total_garbage = 0; 133 134 size_t immediate_garbage = 0; 135 size_t immediate_regions = 0; 136 137 size_t free = 0; 138 size_t free_regions = 0; 139 140 ShenandoahMarkingContext* const ctx = heap->complete_marking_context(); 141 142 for (size_t i = 0; i < num_regions; i++) { 143 ShenandoahHeapRegion* region = heap->get_region(i); 144 145 size_t garbage = region->garbage(); 146 total_garbage += garbage; 147 148 if (region->is_empty()) { 149 free_regions++; 150 free += ShenandoahHeapRegion::region_size_bytes(); 151 } else if (region->is_regular()) { 152 if (!region->has_live()) { 153 // We can recycle it right away and put it in the free set. 154 immediate_regions++; 155 immediate_garbage += garbage; 156 region->make_trash_immediate(); 157 } else { 158 // This is our candidate for later consideration. 159 candidates[cand_idx]._region = region; 160 candidates[cand_idx]._garbage = garbage; 161 cand_idx++; 162 } 163 } else if (region->is_humongous_start()) { 164 // Reclaim humongous regions here, and count them as the immediate garbage 165 #ifdef ASSERT 166 bool reg_live = region->has_live(); 167 bool bm_live = ctx->is_marked(oop(region->bottom() + ShenandoahBrooksPointer::word_size())); 168 assert(reg_live == bm_live, 169 "Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: " SIZE_FORMAT, 170 BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words()); 171 #endif 172 if (!region->has_live()) { 173 heap->trash_humongous_region_at(region); 174 175 // Count only the start. Continuations would be counted on "trash" path 176 immediate_regions++; 177 immediate_garbage += garbage; 178 } 179 } else if (region->is_trash()) { 180 // Count in just trashed collection set, during coalesced CM-with-UR 181 immediate_regions++; 182 immediate_garbage += garbage; 183 } 184 } 185 186 // Step 2. Look back at garbage statistics, and decide if we want to collect anything, 187 // given the amount of immediately reclaimable garbage. If we do, figure out the collection set. 188 189 assert (immediate_garbage <= total_garbage, 190 "Cannot have more immediate garbage than total garbage: " SIZE_FORMAT "M vs " SIZE_FORMAT "M", 191 immediate_garbage / M, total_garbage / M); 192 193 size_t immediate_percent = total_garbage == 0 ? 0 : (immediate_garbage * 100 / total_garbage); 194 195 if (immediate_percent <= ShenandoahImmediateThreshold) { 196 choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free); 197 collection_set->update_region_status(); 198 199 size_t cset_percent = total_garbage == 0 ? 0 : (collection_set->garbage() * 100 / total_garbage); 200 log_info(gc, ergo)("Collectable Garbage: " SIZE_FORMAT "M (" SIZE_FORMAT "%% of total), " SIZE_FORMAT "M CSet, " SIZE_FORMAT " CSet regions", 201 collection_set->garbage() / M, cset_percent, collection_set->live_data() / M, collection_set->count()); 202 } 203 204 log_info(gc, ergo)("Immediate Garbage: " SIZE_FORMAT "M (" SIZE_FORMAT "%% of total), " SIZE_FORMAT " regions", 205 immediate_garbage / M, immediate_percent, immediate_regions); 206 } 207 208 void ShenandoahHeuristics::record_gc_start() { 209 // Do nothing 210 } 211 212 void ShenandoahHeuristics::record_gc_end() { 213 // Do nothing 214 } 215 216 void ShenandoahHeuristics::record_cycle_start() { 217 _cycle_start = os::elapsedTime(); 218 } 219 220 void ShenandoahHeuristics::record_cycle_end() { 221 _last_cycle_end = os::elapsedTime(); 222 } 223 224 void ShenandoahHeuristics::record_phase_time(ShenandoahPhaseTimings::Phase phase, double secs) { 225 // Do nothing 226 } 227 228 bool ShenandoahHeuristics::should_start_update_refs() { 229 return _update_refs_early; 230 } 231 232 bool ShenandoahHeuristics::should_start_normal_gc() const { 233 // Perform GC to cleanup metaspace 234 if (has_metaspace_oom()) { 235 // Some of vmTestbase/metaspace tests depend on following line to count GC cycles 236 log_info(gc)("Trigger: %s", GCCause::to_string(GCCause::_metadata_GC_threshold)); 237 return true; 238 } 239 240 double last_time_ms = (os::elapsedTime() - _last_cycle_end) * 1000; 241 bool periodic_gc = (last_time_ms > ShenandoahGuaranteedGCInterval); 242 if (periodic_gc) { 243 log_info(gc)("Trigger: Time since last GC (%.0f ms) is larger than guaranteed interval (" UINTX_FORMAT " ms)", 244 last_time_ms, ShenandoahGuaranteedGCInterval); 245 } 246 return periodic_gc; 247 } 248 249 bool ShenandoahHeuristics::should_start_traversal_gc() { 250 return false; 251 } 252 253 bool ShenandoahHeuristics::can_do_traversal_gc() { 254 return false; 255 } 256 257 bool ShenandoahHeuristics::should_degenerate_cycle() { 258 return _degenerated_cycles_in_a_row <= ShenandoahFullGCThreshold; 259 } 260 261 void ShenandoahHeuristics::record_success_concurrent() { 262 _degenerated_cycles_in_a_row = 0; 263 _successful_cycles_in_a_row++; 264 265 _gc_time_history->add(time_since_last_gc()); 266 _gc_times_learned++; 267 _gc_time_penalties -= MIN2<size_t>(_gc_time_penalties, Concurrent_Adjust); 268 } 269 270 void ShenandoahHeuristics::record_success_degenerated() { 271 _degenerated_cycles_in_a_row++; 272 _successful_cycles_in_a_row = 0; 273 _gc_time_penalties += Degenerated_Penalty; 274 } 275 276 void ShenandoahHeuristics::record_success_full() { 277 _degenerated_cycles_in_a_row = 0; 278 _successful_cycles_in_a_row++; 279 _gc_time_penalties += Full_Penalty; 280 } 281 282 void ShenandoahHeuristics::record_allocation_failure_gc() { 283 _bytes_in_cset = 0; 284 } 285 286 void ShenandoahHeuristics::record_requested_gc() { 287 _bytes_in_cset = 0; 288 289 // Assume users call System.gc() when external state changes significantly, 290 // which forces us to re-learn the GC timings and allocation rates. 291 _gc_times_learned = 0; 292 } 293 294 bool ShenandoahHeuristics::can_process_references() { 295 if (ShenandoahRefProcFrequency == 0) return false; 296 return true; 297 } 298 299 bool ShenandoahHeuristics::should_process_references() { 300 if (!can_process_references()) return false; 301 size_t cycle = ShenandoahHeap::heap()->shenandoah_policy()->cycle_counter(); 302 // Process references every Nth GC cycle. 303 return cycle % ShenandoahRefProcFrequency == 0; 304 } 305 306 bool ShenandoahHeuristics::can_unload_classes() { 307 if (!ClassUnloading) return false; 308 return true; 309 } 310 311 bool ShenandoahHeuristics::can_unload_classes_normal() { 312 if (!can_unload_classes()) return false; 313 if (has_metaspace_oom()) return true; 314 if (!ClassUnloadingWithConcurrentMark) return false; 315 if (ShenandoahUnloadClassesFrequency == 0) return false; 316 return true; 317 } 318 319 bool ShenandoahHeuristics::should_unload_classes() { 320 if (!can_unload_classes_normal()) return false; 321 if (has_metaspace_oom()) return true; 322 size_t cycle = ShenandoahHeap::heap()->shenandoah_policy()->cycle_counter(); 323 // Unload classes every Nth GC cycle. 324 // This should not happen in the same cycle as process_references to amortize costs. 325 // Offsetting by one is enough to break the rendezvous when periods are equal. 326 // When periods are not equal, offsetting by one is just as good as any other guess. 327 return (cycle + 1) % ShenandoahUnloadClassesFrequency == 0; 328 } 329 330 void ShenandoahHeuristics::initialize() { 331 // Nothing to do by default. 332 } 333 334 double ShenandoahHeuristics::time_since_last_gc() const { 335 return os::elapsedTime() - _cycle_start; 336 }