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