1 /* 2 * Copyright (c) 2013, 2021, Red Hat, Inc. All rights reserved. 3 * Copyright (C) 2022 THL A29 Limited, a Tencent company. 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 "gc/shenandoah/heuristics/shenandoahHeuristics.hpp" 27 #include "gc/shenandoah/mode/shenandoahMode.hpp" 28 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp" 29 #include "gc/shenandoah/shenandoahConcurrentGC.hpp" 30 #include "gc/shenandoah/shenandoahControlThread.hpp" 31 #include "gc/shenandoah/shenandoahDegeneratedGC.hpp" 32 #include "gc/shenandoah/shenandoahFreeSet.hpp" 33 #include "gc/shenandoah/shenandoahFullGC.hpp" 34 #include "gc/shenandoah/shenandoahGeneration.hpp" 35 #include "gc/shenandoah/shenandoahHeap.inline.hpp" 36 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp" 37 #include "gc/shenandoah/shenandoahPacer.inline.hpp" 38 #include "gc/shenandoah/shenandoahUtils.hpp" 39 #include "logging/log.hpp" 40 #include "memory/metaspaceStats.hpp" 41 #include "memory/metaspaceUtils.hpp" 42 43 ShenandoahControlThread::ShenandoahControlThread() : 44 ShenandoahController(), 45 _requested_gc_cause(GCCause::_no_cause_specified), 46 _degen_point(ShenandoahGC::_degenerated_outside_cycle) { 47 set_name("Shenandoah Control Thread"); 48 create_and_start(); 49 } 50 51 void ShenandoahControlThread::run_service() { 52 ShenandoahHeap* const heap = ShenandoahHeap::heap(); 53 const GCMode default_mode = concurrent_normal; 54 const GCCause::Cause default_cause = GCCause::_shenandoah_concurrent_gc; 55 int sleep = ShenandoahControlIntervalMin; 56 57 double last_sleep_adjust_time = os::elapsedTime(); 58 59 ShenandoahCollectorPolicy* const policy = heap->shenandoah_policy(); 60 ShenandoahHeuristics* const heuristics = heap->heuristics(); 61 while (!should_terminate()) { 62 const GCCause::Cause cancelled_cause = heap->cancelled_cause(); 63 if (cancelled_cause == GCCause::_shenandoah_stop_vm) { 64 break; 65 } 66 67 // Figure out if we have pending requests. 68 const bool alloc_failure_pending = ShenandoahCollectorPolicy::is_allocation_failure(cancelled_cause); 69 const bool is_gc_requested = _gc_requested.is_set(); 70 const GCCause::Cause requested_gc_cause = _requested_gc_cause; 71 72 // This control loop iteration has seen this much allocation. 73 const size_t allocs_seen = reset_allocs_seen(); 74 75 // Choose which GC mode to run in. The block below should select a single mode. 76 GCMode mode = none; 77 GCCause::Cause cause = GCCause::_last_gc_cause; 78 ShenandoahGC::ShenandoahDegenPoint degen_point = ShenandoahGC::_degenerated_unset; 79 80 if (alloc_failure_pending) { 81 // Allocation failure takes precedence: we have to deal with it first thing 82 heuristics->log_trigger("Handle Allocation Failure"); 83 84 cause = GCCause::_allocation_failure; 85 86 // Consume the degen point, and seed it with default value 87 degen_point = _degen_point; 88 _degen_point = ShenandoahGC::_degenerated_outside_cycle; 89 90 if (ShenandoahDegeneratedGC && heuristics->should_degenerate_cycle()) { 91 heuristics->record_allocation_failure_gc(); 92 policy->record_alloc_failure_to_degenerated(degen_point); 93 mode = stw_degenerated; 94 } else { 95 heuristics->record_allocation_failure_gc(); 96 policy->record_alloc_failure_to_full(); 97 mode = stw_full; 98 } 99 } else if (is_gc_requested) { 100 cause = requested_gc_cause; 101 heuristics->log_trigger("GC request (%s)", GCCause::to_string(cause)); 102 heuristics->record_requested_gc(); 103 104 if (ShenandoahCollectorPolicy::should_run_full_gc(cause)) { 105 mode = stw_full; 106 } else { 107 mode = default_mode; 108 // Unload and clean up everything 109 heap->set_unload_classes(heuristics->can_unload_classes()); 110 } 111 } else { 112 // Potential normal cycle: ask heuristics if it wants to act 113 if (heuristics->should_start_gc()) { 114 mode = default_mode; 115 cause = default_cause; 116 } 117 118 // Ask policy if this cycle wants to process references or unload classes 119 heap->set_unload_classes(heuristics->should_unload_classes()); 120 } 121 122 // Blow all soft references on this cycle, if handling allocation failure, 123 // either implicit or explicit GC request, or we are requested to do so unconditionally. 124 if (alloc_failure_pending || is_gc_requested || ShenandoahAlwaysClearSoftRefs) { 125 heap->soft_ref_policy()->set_should_clear_all_soft_refs(true); 126 } 127 128 const bool gc_requested = (mode != none); 129 assert (!gc_requested || cause != GCCause::_last_gc_cause, "GC cause should be set"); 130 131 if (gc_requested) { 132 // Cannot uncommit bitmap slices during concurrent reset 133 ShenandoahNoUncommitMark forbid_region_uncommit(heap); 134 135 // GC is starting, bump the internal ID 136 update_gc_id(); 137 138 GCIdMark gc_id_mark; 139 140 heuristics->cancel_trigger_request(); 141 142 heap->reset_bytes_allocated_since_gc_start(); 143 144 MetaspaceCombinedStats meta_sizes = MetaspaceUtils::get_combined_statistics(); 145 146 // If GC was requested, we are sampling the counters even without actual triggers 147 // from allocation machinery. This captures GC phases more accurately. 148 heap->set_forced_counters_update(true); 149 150 // If GC was requested, we better dump freeset data for performance debugging 151 heap->free_set()->log_status_under_lock(); 152 153 switch (mode) { 154 case concurrent_normal: 155 service_concurrent_normal_cycle(cause); 156 break; 157 case stw_degenerated: 158 service_stw_degenerated_cycle(cause, degen_point); 159 break; 160 case stw_full: 161 service_stw_full_cycle(cause); 162 break; 163 default: 164 ShouldNotReachHere(); 165 } 166 167 // If this was the requested GC cycle, notify waiters about it 168 if (is_gc_requested) { 169 notify_gc_waiters(); 170 } 171 172 // If this cycle completed without being cancelled, notify waiters about it 173 if (!heap->cancelled_gc()) { 174 notify_alloc_failure_waiters(); 175 } 176 177 // Report current free set state at the end of cycle, whether 178 // it is a normal completion, or the abort. 179 heap->free_set()->log_status_under_lock(); 180 181 { 182 // Notify Universe about new heap usage. This has implications for 183 // global soft refs policy, and we better report it every time heap 184 // usage goes down. 185 ShenandoahHeapLocker locker(heap->lock()); 186 heap->update_capacity_and_used_at_gc(); 187 } 188 189 // Signal that we have completed a visit to all live objects. 190 heap->record_whole_heap_examined_timestamp(); 191 192 // Disable forced counters update, and update counters one more time 193 // to capture the state at the end of GC session. 194 heap->handle_force_counters_update(); 195 heap->set_forced_counters_update(false); 196 197 // Retract forceful part of soft refs policy 198 heap->soft_ref_policy()->set_should_clear_all_soft_refs(false); 199 200 // Clear metaspace oom flag, if current cycle unloaded classes 201 if (heap->unload_classes()) { 202 heuristics->clear_metaspace_oom(); 203 } 204 205 // Commit worker statistics to cycle data 206 heap->phase_timings()->flush_par_workers_to_cycle(); 207 if (ShenandoahPacing) { 208 heap->pacer()->flush_stats_to_cycle(); 209 } 210 211 // Print GC stats for current cycle 212 { 213 LogTarget(Info, gc, stats) lt; 214 if (lt.is_enabled()) { 215 ResourceMark rm; 216 LogStream ls(lt); 217 heap->phase_timings()->print_cycle_on(&ls); 218 if (ShenandoahPacing) { 219 heap->pacer()->print_cycle_on(&ls); 220 } 221 } 222 } 223 224 // Commit statistics to globals 225 heap->phase_timings()->flush_cycle_to_global(); 226 227 // Print Metaspace change following GC (if logging is enabled). 228 MetaspaceUtils::print_metaspace_change(meta_sizes); 229 230 // GC is over, we are at idle now 231 if (ShenandoahPacing) { 232 heap->pacer()->setup_for_idle(); 233 } 234 } else { 235 // Report to pacer that we have seen this many words allocated 236 if (ShenandoahPacing && (allocs_seen > 0)) { 237 heap->pacer()->report_alloc(allocs_seen); 238 } 239 } 240 241 // Check if we have seen a new target for soft max heap size or if a gc was requested. 242 // Either of these conditions will attempt to uncommit regions. 243 if (ShenandoahUncommit) { 244 if (heap->check_soft_max_changed()) { 245 heap->notify_soft_max_changed(); 246 } else if (is_gc_requested) { 247 heap->notify_explicit_gc_requested(); 248 } 249 } 250 251 // Wait before performing the next action. If allocation happened during this wait, 252 // we exit sooner, to let heuristics re-evaluate new conditions. If we are at idle, 253 // back off exponentially. 254 const double current = os::elapsedTime(); 255 if (heap->has_changed()) { 256 sleep = ShenandoahControlIntervalMin; 257 } else if ((current - last_sleep_adjust_time) * 1000 > ShenandoahControlIntervalAdjustPeriod){ 258 sleep = MIN2<int>(ShenandoahControlIntervalMax, MAX2(1, sleep * 2)); 259 last_sleep_adjust_time = current; 260 } 261 os::naked_short_sleep(sleep); 262 } 263 } 264 265 void ShenandoahControlThread::service_concurrent_normal_cycle(GCCause::Cause cause) { 266 // Normal cycle goes via all concurrent phases. If allocation failure (af) happens during 267 // any of the concurrent phases, it first degrades to Degenerated GC and completes GC there. 268 // If second allocation failure happens during Degenerated GC cycle (for example, when GC 269 // tries to evac something and no memory is available), cycle degrades to Full GC. 270 // 271 // There are also a shortcut through the normal cycle: immediate garbage shortcut, when 272 // heuristics says there are no regions to compact, and all the collection comes from immediately 273 // reclaimable regions. 274 // 275 // ................................................................................................ 276 // 277 // (immediate garbage shortcut) Concurrent GC 278 // /-------------------------------------------\ 279 // | | 280 // | | 281 // | | 282 // | v 283 // [START] ----> Conc Mark ----o----> Conc Evac --o--> Conc Update-Refs ---o----> [END] 284 // | | | ^ 285 // | (af) | (af) | (af) | 286 // ..................|....................|.................|..............|....................... 287 // | | | | 288 // | | | | Degenerated GC 289 // v v v | 290 // STW Mark ----------> STW Evac ----> STW Update-Refs ----->o 291 // | | | ^ 292 // | (af) | (af) | (af) | 293 // ..................|....................|.................|..............|....................... 294 // | | | | 295 // | v | | Full GC 296 // \------------------->o<----------------/ | 297 // | | 298 // v | 299 // Full GC --------------------------/ 300 // 301 ShenandoahHeap* heap = ShenandoahHeap::heap(); 302 if (check_cancellation_or_degen(ShenandoahGC::_degenerated_outside_cycle)) { 303 log_info(gc)("Cancelled"); 304 return; 305 } 306 307 ShenandoahGCSession session(cause, heap->global_generation()); 308 309 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters()); 310 311 ShenandoahConcurrentGC gc(heap->global_generation(), false); 312 if (gc.collect(cause)) { 313 // Cycle is complete. There were no failed allocation requests and no degeneration, so count this as good progress. 314 heap->notify_gc_progress(); 315 heap->global_generation()->heuristics()->record_success_concurrent(); 316 heap->shenandoah_policy()->record_success_concurrent(false, gc.abbreviated()); 317 heap->log_heap_status("At end of GC"); 318 } else { 319 assert(heap->cancelled_gc(), "Must have been cancelled"); 320 check_cancellation_or_degen(gc.degen_point()); 321 heap->log_heap_status("At end of cancelled GC"); 322 } 323 } 324 325 bool ShenandoahControlThread::check_cancellation_or_degen(ShenandoahGC::ShenandoahDegenPoint point) { 326 ShenandoahHeap* heap = ShenandoahHeap::heap(); 327 if (heap->cancelled_gc()) { 328 if (heap->cancelled_cause() == GCCause::_shenandoah_stop_vm) { 329 return true; 330 } 331 332 if (ShenandoahCollectorPolicy::is_allocation_failure(heap->cancelled_cause())) { 333 assert (_degen_point == ShenandoahGC::_degenerated_outside_cycle, 334 "Should not be set yet: %s", ShenandoahGC::degen_point_to_string(_degen_point)); 335 _degen_point = point; 336 return true; 337 } 338 339 fatal("Unexpected reason for cancellation: %s", GCCause::to_string(heap->cancelled_cause())); 340 } 341 return false; 342 } 343 344 void ShenandoahControlThread::stop_service() { 345 ShenandoahHeap::heap()->cancel_gc(GCCause::_shenandoah_stop_vm); 346 } 347 348 void ShenandoahControlThread::service_stw_full_cycle(GCCause::Cause cause) { 349 ShenandoahHeap* const heap = ShenandoahHeap::heap(); 350 ShenandoahGCSession session(cause, heap->global_generation()); 351 352 ShenandoahFullGC gc; 353 gc.collect(cause); 354 } 355 356 void ShenandoahControlThread::service_stw_degenerated_cycle(GCCause::Cause cause, ShenandoahGC::ShenandoahDegenPoint point) { 357 assert (point != ShenandoahGC::_degenerated_unset, "Degenerated point should be set"); 358 ShenandoahHeap* const heap = ShenandoahHeap::heap(); 359 ShenandoahGCSession session(cause, heap->global_generation()); 360 361 ShenandoahDegenGC gc(point, heap->global_generation()); 362 gc.collect(cause); 363 } 364 365 void ShenandoahControlThread::request_gc(GCCause::Cause cause) { 366 if (ShenandoahCollectorPolicy::should_handle_requested_gc(cause)) { 367 handle_requested_gc(cause); 368 } 369 } 370 371 void ShenandoahControlThread::handle_requested_gc(GCCause::Cause cause) { 372 if (should_terminate()) { 373 log_info(gc)("Control thread is terminating, no more GCs"); 374 return; 375 } 376 377 // For normal requested GCs (System.gc) we want to block the caller. However, 378 // for whitebox requested GC, we want to initiate the GC and return immediately. 379 // The whitebox caller thread will arrange for itself to wait until the GC notifies 380 // it that has reached the requested breakpoint (phase in the GC). 381 if (cause == GCCause::_wb_breakpoint) { 382 _requested_gc_cause = cause; 383 _gc_requested.set(); 384 return; 385 } 386 387 // Make sure we have at least one complete GC cycle before unblocking 388 // from the explicit GC request. 389 // 390 // This is especially important for weak references cleanup and/or native 391 // resources (e.g. DirectByteBuffers) machinery: when explicit GC request 392 // comes very late in the already running cycle, it would miss lots of new 393 // opportunities for cleanup that were made available before the caller 394 // requested the GC. 395 396 MonitorLocker ml(&_gc_waiters_lock); 397 size_t current_gc_id = get_gc_id(); 398 size_t required_gc_id = current_gc_id + 1; 399 while (current_gc_id < required_gc_id && !should_terminate()) { 400 // Although setting gc request is under _gc_waiters_lock, but read side (run_service()) 401 // does not take the lock. We need to enforce following order, so that read side sees 402 // latest requested gc cause when the flag is set. 403 _requested_gc_cause = cause; 404 _gc_requested.set(); 405 406 ml.wait(); 407 current_gc_id = get_gc_id(); 408 } 409 } 410 411 void ShenandoahControlThread::notify_gc_waiters() { 412 _gc_requested.unset(); 413 MonitorLocker ml(&_gc_waiters_lock); 414 ml.notify_all(); 415 }