| /* |
| * Copyright (c) 2013, 2021, Red Hat, Inc. All rights reserved. |
| * Copyright (C) 2022, Tencent. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp" |
| #include "gc/shenandoah/mode/shenandoahMode.hpp" |
| #include "gc/shenandoah/shenandoahCollectorPolicy.hpp" |
| #include "gc/shenandoah/shenandoahConcurrentGC.hpp" |
| #include "gc/shenandoah/shenandoahControlThread.hpp" |
| #include "gc/shenandoah/shenandoahDegeneratedGC.hpp" |
| #include "gc/shenandoah/shenandoahFreeSet.hpp" |
| #include "gc/shenandoah/shenandoahFullGC.hpp" |
| #include "gc/shenandoah/shenandoahGeneration.hpp" |
| #include "gc/shenandoah/shenandoahHeap.inline.hpp" |
| #include "gc/shenandoah/shenandoahMonitoringSupport.hpp" |
| #include "gc/shenandoah/shenandoahPacer.inline.hpp" |
| #include "gc/shenandoah/shenandoahUtils.hpp" |
| #include "logging/log.hpp" |
| #include "memory/metaspaceStats.hpp" |
| #include "memory/metaspaceUtils.hpp" |
| |
| ShenandoahControlThread::ShenandoahControlThread() : |
| ShenandoahController(), |
| _requested_gc_cause(GCCause::_no_cause_specified), |
| _degen_point(ShenandoahGC::_degenerated_outside_cycle) { |
| set_name("Shenandoah Control Thread"); |
| create_and_start(); |
| } |
| |
| void ShenandoahControlThread::run_service() { |
| ShenandoahHeap* const heap = ShenandoahHeap::heap(); |
| const GCMode default_mode = concurrent_normal; |
| const GCCause::Cause default_cause = GCCause::_shenandoah_concurrent_gc; |
| int sleep = ShenandoahControlIntervalMin; |
| |
| double last_sleep_adjust_time = os::elapsedTime(); |
| |
| ShenandoahCollectorPolicy* const policy = heap->shenandoah_policy(); |
| ShenandoahHeuristics* const heuristics = heap->heuristics(); |
| while (!should_terminate()) { |
| const GCCause::Cause cancelled_cause = heap->cancelled_cause(); |
| if (cancelled_cause == GCCause::_shenandoah_stop_vm) { |
| break; |
| } |
| |
| // Figure out if we have pending requests. |
| const bool alloc_failure_pending = ShenandoahCollectorPolicy::is_allocation_failure(cancelled_cause); |
| const bool is_gc_requested = _gc_requested.is_set(); |
| const GCCause::Cause requested_gc_cause = _requested_gc_cause; |
| |
| // This control loop iteration has seen this much allocation. |
| const size_t allocs_seen = reset_allocs_seen(); |
| |
| // Choose which GC mode to run in. The block below should select a single mode. |
| GCMode mode = none; |
| GCCause::Cause cause = GCCause::_last_gc_cause; |
| ShenandoahGC::ShenandoahDegenPoint degen_point = ShenandoahGC::_degenerated_unset; |
| |
| if (alloc_failure_pending) { |
| // Allocation failure takes precedence: we have to deal with it first thing |
| heuristics->log_trigger("Handle Allocation Failure"); |
| |
| cause = GCCause::_allocation_failure; |
| |
| // Consume the degen point, and seed it with default value |
| degen_point = _degen_point; |
| _degen_point = ShenandoahGC::_degenerated_outside_cycle; |
| |
| if (ShenandoahDegeneratedGC && heuristics->should_degenerate_cycle()) { |
| heuristics->record_allocation_failure_gc(); |
| policy->record_alloc_failure_to_degenerated(degen_point); |
| mode = stw_degenerated; |
| } else { |
| heuristics->record_allocation_failure_gc(); |
| policy->record_alloc_failure_to_full(); |
| mode = stw_full; |
| } |
| } else if (is_gc_requested) { |
| cause = requested_gc_cause; |
| heuristics->log_trigger("GC request (%s)", GCCause::to_string(cause)); |
| heuristics->record_requested_gc(); |
| |
| if (ShenandoahCollectorPolicy::should_run_full_gc(cause)) { |
| mode = stw_full; |
| } else { |
| mode = default_mode; |
| // Unload and clean up everything |
| heap->set_unload_classes(heuristics->can_unload_classes()); |
| } |
| } else { |
| // Potential normal cycle: ask heuristics if it wants to act |
| if (heuristics->should_start_gc()) { |
| mode = default_mode; |
| cause = default_cause; |
| } |
| |
| // Ask policy if this cycle wants to process references or unload classes |
| heap->set_unload_classes(heuristics->should_unload_classes()); |
| } |
| |
| // Blow all soft references on this cycle, if handling allocation failure, |
| // either implicit or explicit GC request, or we are requested to do so unconditionally. |
| if (alloc_failure_pending || is_gc_requested || ShenandoahAlwaysClearSoftRefs) { |
| heap->soft_ref_policy()->set_should_clear_all_soft_refs(true); |
| } |
| |
| const bool gc_requested = (mode != none); |
| assert (!gc_requested || cause != GCCause::_last_gc_cause, "GC cause should be set"); |
| |
| if (gc_requested) { |
| // Cannot uncommit bitmap slices during concurrent reset |
| ShenandoahNoUncommitMark forbid_region_uncommit(heap); |
| |
| // GC is starting, bump the internal ID |
| update_gc_id(); |
| |
| GCIdMark gc_id_mark; |
| |
| heuristics->cancel_trigger_request(); |
| |
| heap->reset_bytes_allocated_since_gc_start(); |
| |
| MetaspaceCombinedStats meta_sizes = MetaspaceUtils::get_combined_statistics(); |
| |
| // If GC was requested, we are sampling the counters even without actual triggers |
| // from allocation machinery. This captures GC phases more accurately. |
| heap->set_forced_counters_update(true); |
| |
| // If GC was requested, we better dump freeset data for performance debugging |
| heap->free_set()->log_status_under_lock(); |
| |
| switch (mode) { |
| case concurrent_normal: |
| service_concurrent_normal_cycle(cause); |
| break; |
| case stw_degenerated: |
| service_stw_degenerated_cycle(cause, degen_point); |
| break; |
| case stw_full: |
| service_stw_full_cycle(cause); |
| break; |
| default: |
| ShouldNotReachHere(); |
| } |
| |
| // If this was the requested GC cycle, notify waiters about it |
| if (is_gc_requested) { |
| notify_gc_waiters(); |
| } |
| |
| // If this cycle completed without being cancelled, notify waiters about it |
| if (!heap->cancelled_gc()) { |
| notify_alloc_failure_waiters(); |
| } |
| |
| // Report current free set state at the end of cycle, whether |
| // it is a normal completion, or the abort. |
| heap->free_set()->log_status_under_lock(); |
| |
| { |
| // Notify Universe about new heap usage. This has implications for |
| // global soft refs policy, and we better report it every time heap |
| // usage goes down. |
| ShenandoahHeapLocker locker(heap->lock()); |
| heap->update_capacity_and_used_at_gc(); |
| } |
| |
| // Signal that we have completed a visit to all live objects. |
| heap->record_whole_heap_examined_timestamp(); |
| |
| // Disable forced counters update, and update counters one more time |
| // to capture the state at the end of GC session. |
| heap->handle_force_counters_update(); |
| heap->set_forced_counters_update(false); |
| |
| // Retract forceful part of soft refs policy |
| heap->soft_ref_policy()->set_should_clear_all_soft_refs(false); |
| |
| // Clear metaspace oom flag, if current cycle unloaded classes |
| if (heap->unload_classes()) { |
| heuristics->clear_metaspace_oom(); |
| } |
| |
| // Commit worker statistics to cycle data |
| heap->phase_timings()->flush_par_workers_to_cycle(); |
| if (ShenandoahPacing) { |
| heap->pacer()->flush_stats_to_cycle(); |
| } |
| |
| // Print GC stats for current cycle |
| { |
| LogTarget(Info, gc, stats) lt; |
| if (lt.is_enabled()) { |
| ResourceMark rm; |
| LogStream ls(lt); |
| heap->phase_timings()->print_cycle_on(&ls); |
| if (ShenandoahPacing) { |
| heap->pacer()->print_cycle_on(&ls); |
| } |
| } |
| } |
| |
| // Commit statistics to globals |
| heap->phase_timings()->flush_cycle_to_global(); |
| |
| // Print Metaspace change following GC (if logging is enabled). |
| MetaspaceUtils::print_metaspace_change(meta_sizes); |
| |
| // GC is over, we are at idle now |
| if (ShenandoahPacing) { |
| heap->pacer()->setup_for_idle(); |
| } |
| } else { |
| // Report to pacer that we have seen this many words allocated |
| if (ShenandoahPacing && (allocs_seen > 0)) { |
| heap->pacer()->report_alloc(allocs_seen); |
| } |
| } |
| |
| // Check if we have seen a new target for soft max heap size or if a gc was requested. |
| // Either of these conditions will attempt to uncommit regions. |
| if (ShenandoahUncommit) { |
| if (heap->check_soft_max_changed()) { |
| heap->notify_soft_max_changed(); |
| } else if (is_gc_requested) { |
| heap->notify_explicit_gc_requested(); |
| } |
| } |
| |
| // Wait before performing the next action. If allocation happened during this wait, |
| // we exit sooner, to let heuristics re-evaluate new conditions. If we are at idle, |
| // back off exponentially. |
| const double current = os::elapsedTime(); |
| if (heap->has_changed()) { |
| sleep = ShenandoahControlIntervalMin; |
| } else if ((current - last_sleep_adjust_time) * 1000 > ShenandoahControlIntervalAdjustPeriod){ |
| sleep = MIN2<int>(ShenandoahControlIntervalMax, MAX2(1, sleep * 2)); |
| last_sleep_adjust_time = current; |
| } |
| os::naked_short_sleep(sleep); |
| } |
| } |
| |
| void ShenandoahControlThread::service_concurrent_normal_cycle(GCCause::Cause cause) { |
| // Normal cycle goes via all concurrent phases. If allocation failure (af) happens during |
| // any of the concurrent phases, it first degrades to Degenerated GC and completes GC there. |
| // If second allocation failure happens during Degenerated GC cycle (for example, when GC |
| // tries to evac something and no memory is available), cycle degrades to Full GC. |
| // |
| // There are also a shortcut through the normal cycle: immediate garbage shortcut, when |
| // heuristics says there are no regions to compact, and all the collection comes from immediately |
| // reclaimable regions. |
| // |
| // ................................................................................................ |
| // |
| // (immediate garbage shortcut) Concurrent GC |
| // /-------------------------------------------\ |
| // | | |
| // | | |
| // | | |
| // | v |
| // [START] ----> Conc Mark ----o----> Conc Evac --o--> Conc Update-Refs ---o----> [END] |
| // | | | ^ |
| // | (af) | (af) | (af) | |
| // ..................|....................|.................|..............|....................... |
| // | | | | |
| // | | | | Degenerated GC |
| // v v v | |
| // STW Mark ----------> STW Evac ----> STW Update-Refs ----->o |
| // | | | ^ |
| // | (af) | (af) | (af) | |
| // ..................|....................|.................|..............|....................... |
| // | | | | |
| // | v | | Full GC |
| // \------------------->o<----------------/ | |
| // | | |
| // v | |
| // Full GC --------------------------/ |
| // |
| ShenandoahHeap* heap = ShenandoahHeap::heap(); |
| if (check_cancellation_or_degen(ShenandoahGC::_degenerated_outside_cycle)) { |
| log_info(gc)("Cancelled"); |
| return; |
| } |
| |
| ShenandoahGCSession session(cause, heap->global_generation()); |
| |
| TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters()); |
| |
| ShenandoahConcurrentGC gc(heap->global_generation(), false); |
| if (gc.collect(cause)) { |
| // Cycle is complete. There were no failed allocation requests and no degeneration, so count this as good progress. |
| heap->notify_gc_progress(); |
| heap->global_generation()->heuristics()->record_success_concurrent(); |
| heap->shenandoah_policy()->record_success_concurrent(false, gc.abbreviated()); |
| heap->log_heap_status("At end of GC"); |
| } else { |
| assert(heap->cancelled_gc(), "Must have been cancelled"); |
| check_cancellation_or_degen(gc.degen_point()); |
| heap->log_heap_status("At end of cancelled GC"); |
| } |
| } |
| |
| bool ShenandoahControlThread::check_cancellation_or_degen(ShenandoahGC::ShenandoahDegenPoint point) { |
| ShenandoahHeap* heap = ShenandoahHeap::heap(); |
| if (heap->cancelled_gc()) { |
| if (heap->cancelled_cause() == GCCause::_shenandoah_stop_vm) { |
| return true; |
| } |
| |
| if (ShenandoahCollectorPolicy::is_allocation_failure(heap->cancelled_cause())) { |
| assert (_degen_point == ShenandoahGC::_degenerated_outside_cycle, |
| "Should not be set yet: %s", ShenandoahGC::degen_point_to_string(_degen_point)); |
| _degen_point = point; |
| return true; |
| } |
| |
| fatal("Unexpected reason for cancellation: %s", GCCause::to_string(heap->cancelled_cause())); |
| } |
| return false; |
| } |
| |
| void ShenandoahControlThread::stop_service() { |
| ShenandoahHeap::heap()->cancel_gc(GCCause::_shenandoah_stop_vm); |
| } |
| |
| void ShenandoahControlThread::service_stw_full_cycle(GCCause::Cause cause) { |
| ShenandoahHeap* const heap = ShenandoahHeap::heap(); |
| ShenandoahGCSession session(cause, heap->global_generation()); |
| |
| ShenandoahFullGC gc; |
| gc.collect(cause); |
| } |
| |
| void ShenandoahControlThread::service_stw_degenerated_cycle(GCCause::Cause cause, ShenandoahGC::ShenandoahDegenPoint point) { |
| assert (point != ShenandoahGC::_degenerated_unset, "Degenerated point should be set"); |
| ShenandoahHeap* const heap = ShenandoahHeap::heap(); |
| ShenandoahGCSession session(cause, heap->global_generation()); |
| |
| ShenandoahDegenGC gc(point, heap->global_generation()); |
| gc.collect(cause); |
| } |
| |
| void ShenandoahControlThread::request_gc(GCCause::Cause cause) { |
| if (ShenandoahCollectorPolicy::should_handle_requested_gc(cause)) { |
| handle_requested_gc(cause); |
| } |
| } |
| |
| void ShenandoahControlThread::handle_requested_gc(GCCause::Cause cause) { |
| if (should_terminate()) { |
| log_info(gc)("Control thread is terminating, no more GCs"); |
| return; |
| } |
| |
| // For normal requested GCs (System.gc) we want to block the caller. However, |
| // for whitebox requested GC, we want to initiate the GC and return immediately. |
| // The whitebox caller thread will arrange for itself to wait until the GC notifies |
| // it that has reached the requested breakpoint (phase in the GC). |
| if (cause == GCCause::_wb_breakpoint) { |
| _requested_gc_cause = cause; |
| _gc_requested.set(); |
| return; |
| } |
| |
| // Make sure we have at least one complete GC cycle before unblocking |
| // from the explicit GC request. |
| // |
| // This is especially important for weak references cleanup and/or native |
| // resources (e.g. DirectByteBuffers) machinery: when explicit GC request |
| // comes very late in the already running cycle, it would miss lots of new |
| // opportunities for cleanup that were made available before the caller |
| // requested the GC. |
| |
| MonitorLocker ml(&_gc_waiters_lock); |
| size_t current_gc_id = get_gc_id(); |
| size_t required_gc_id = current_gc_id + 1; |
| while (current_gc_id < required_gc_id && !should_terminate()) { |
| // Although setting gc request is under _gc_waiters_lock, but read side (run_service()) |
| // does not take the lock. We need to enforce following order, so that read side sees |
| // latest requested gc cause when the flag is set. |
| _requested_gc_cause = cause; |
| _gc_requested.set(); |
| |
| ml.wait(); |
| current_gc_id = get_gc_id(); |
| } |
| } |
| |
| void ShenandoahControlThread::notify_gc_waiters() { |
| _gc_requested.unset(); |
| MonitorLocker ml(&_gc_waiters_lock); |
| ml.notify_all(); |
| } |
