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/*
* Copyright (c) 2021, Red Hat, Inc. All rights reserved.
+ * Copyright Amazon.com Inc. or its affiliates. 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.
#include "gc/shared/collectorCounters.hpp"
#include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
#include "gc/shenandoah/shenandoahConcurrentMark.hpp"
#include "gc/shenandoah/shenandoahDegeneratedGC.hpp"
#include "gc/shenandoah/shenandoahFullGC.hpp"
#include "gc/shenandoah/shenandoahHeap.inline.hpp"
#include "gc/shenandoah/shenandoahMetrics.hpp"
#include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
#include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
#include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
#include "gc/shenandoah/shenandoahSTWMark.hpp"
#include "gc/shenandoah/shenandoahUtils.hpp"
#include "gc/shenandoah/shenandoahVerifier.hpp"
#include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
#include "gc/shenandoah/shenandoahVMOperations.hpp"
#include "runtime/vmThread.hpp"
#include "utilities/events.hpp"
! ShenandoahDegenGC::ShenandoahDegenGC(ShenandoahDegenPoint degen_point) :
ShenandoahGC(),
! _degen_point(degen_point) {
}
bool ShenandoahDegenGC::collect(GCCause::Cause cause) {
vmop_degenerated();
return true;
}
void ShenandoahDegenGC::vmop_degenerated() {
TraceCollectorStats tcs(ShenandoahHeap::heap()->monitoring_support()->full_stw_collection_counters());
#include "gc/shared/collectorCounters.hpp"
#include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
#include "gc/shenandoah/shenandoahConcurrentMark.hpp"
#include "gc/shenandoah/shenandoahDegeneratedGC.hpp"
#include "gc/shenandoah/shenandoahFullGC.hpp"
+ #include "gc/shenandoah/shenandoahGeneration.hpp"
+ #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
#include "gc/shenandoah/shenandoahHeap.inline.hpp"
#include "gc/shenandoah/shenandoahMetrics.hpp"
#include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
+ #include "gc/shenandoah/shenandoahOldGeneration.hpp"
#include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
#include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
#include "gc/shenandoah/shenandoahSTWMark.hpp"
#include "gc/shenandoah/shenandoahUtils.hpp"
#include "gc/shenandoah/shenandoahVerifier.hpp"
+ #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
#include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
#include "gc/shenandoah/shenandoahVMOperations.hpp"
#include "runtime/vmThread.hpp"
#include "utilities/events.hpp"
! ShenandoahDegenGC::ShenandoahDegenGC(ShenandoahDegenPoint degen_point, ShenandoahGeneration* generation) :
ShenandoahGC(),
! _degen_point(degen_point),
+ _generation(generation),
+ _abbreviated(false) {
}
bool ShenandoahDegenGC::collect(GCCause::Cause cause) {
vmop_degenerated();
+ ShenandoahHeap* heap = ShenandoahHeap::heap();
+ if (heap->mode()->is_generational()) {
+ bool is_bootstrap_gc = heap->old_generation()->is_bootstrapping();
+ heap->mmu_tracker()->record_degenerated(GCId::current(), is_bootstrap_gc);
+ const char* msg = is_bootstrap_gc? "At end of Degenerated Bootstrap Old GC": "At end of Degenerated Young GC";
+ heap->log_heap_status(msg);
+ }
return true;
}
void ShenandoahDegenGC::vmop_degenerated() {
TraceCollectorStats tcs(ShenandoahHeap::heap()->monitoring_support()->full_stw_collection_counters());
void ShenandoahDegenGC::entry_degenerated() {
const char* msg = degen_event_message(_degen_point);
ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::degen_gc, true /* log_heap_usage */);
EventMark em("%s", msg);
ShenandoahHeap* const heap = ShenandoahHeap::heap();
-
ShenandoahWorkerScope scope(heap->workers(),
ShenandoahWorkerPolicy::calc_workers_for_stw_degenerated(),
"stw degenerated gc");
heap->set_degenerated_gc_in_progress(true);
void ShenandoahDegenGC::op_degenerated() {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
// Degenerated GC is STW, but it can also fail. Current mechanics communicates
// GC failure via cancelled_concgc() flag. So, if we detect the failure after
// some phase, we have to upgrade the Degenerate GC to Full GC.
! heap->clear_cancelled_gc();
ShenandoahMetricsSnapshot metrics;
metrics.snap_before();
switch (_degen_point) {
void ShenandoahDegenGC::op_degenerated() {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
// Degenerated GC is STW, but it can also fail. Current mechanics communicates
// GC failure via cancelled_concgc() flag. So, if we detect the failure after
// some phase, we have to upgrade the Degenerate GC to Full GC.
! heap->clear_cancelled_gc(true /* clear oom handler */);
+
+ #ifdef ASSERT
+ if (heap->mode()->is_generational()) {
+ ShenandoahOldGeneration* old_generation = heap->old_generation();
+ if (!heap->is_concurrent_old_mark_in_progress()) {
+ // If we are not marking the old generation, there should be nothing in the old mark queues
+ assert(old_generation->task_queues()->is_empty(), "Old gen task queues should be empty");
+ }
+
+ if (_generation->is_global()) {
+ // If we are in a global cycle, the old generation should not be marking. It is, however,
+ // allowed to be holding regions for evacuation or coalescing.
+ assert(old_generation->is_idle()
+ || old_generation->is_doing_mixed_evacuations()
+ || old_generation->is_preparing_for_mark(),
+ "Old generation cannot be in state: %s", old_generation->state_name());
+ }
+ }
+ #endif
ShenandoahMetricsSnapshot metrics;
metrics.snap_before();
switch (_degen_point) {
// We have degenerated from outside the cycle, which means something is bad with
// the heap, most probably heavy humongous fragmentation, or we are very low on free
// space. It makes little sense to wait for Full GC to reclaim as much as it can, when
// we can do the most aggressive degen cycle, which includes processing references and
// class unloading, unless those features are explicitly disabled.
- //
-
- // Degenerated from concurrent root mark, reset the flag for STW mark
- if (heap->is_concurrent_mark_in_progress()) {
- ShenandoahConcurrentMark::cancel();
- heap->set_concurrent_mark_in_progress(false);
- }
// Note that we can only do this for "outside-cycle" degens, otherwise we would risk
// changing the cycle parameters mid-cycle during concurrent -> degenerated handover.
! heap->set_unload_classes(heap->heuristics()->can_unload_classes());
op_reset();
// STW mark
op_mark();
// We have degenerated from outside the cycle, which means something is bad with
// the heap, most probably heavy humongous fragmentation, or we are very low on free
// space. It makes little sense to wait for Full GC to reclaim as much as it can, when
// we can do the most aggressive degen cycle, which includes processing references and
// class unloading, unless those features are explicitly disabled.
// Note that we can only do this for "outside-cycle" degens, otherwise we would risk
// changing the cycle parameters mid-cycle during concurrent -> degenerated handover.
! heap->set_unload_classes(_generation->heuristics()->can_unload_classes() &&
+ (!heap->mode()->is_generational() || _generation->is_global()));
+
+ if (heap->mode()->is_generational() && _generation->is_young()) {
+ // Swap remembered sets for young
+ _generation->swap_remembered_set();
+ }
+
+ case _degenerated_roots:
+ // Degenerated from concurrent root mark, reset the flag for STW mark
+ if (!heap->mode()->is_generational()) {
+ if (heap->is_concurrent_mark_in_progress()) {
+ heap->cancel_concurrent_mark();
+ }
+ } else {
+ if (_generation->is_concurrent_mark_in_progress()) {
+ // We want to allow old generation marking to be punctuated by young collections
+ // (even if they have degenerated). If this is a global cycle, we'd have cancelled
+ // the entire old gc before coming into this switch. Note that cancel_marking on
+ // the generation does NOT abandon incomplete SATB buffers as cancel_concurrent_mark does.
+ // We need to separate out the old pointers which is done below.
+ _generation->cancel_marking();
+ }
+
+ if (heap->is_concurrent_mark_in_progress()) {
+ // If either old or young marking is in progress, the SATB barrier will be enabled.
+ // The SATB buffer may hold a mix of old and young pointers. The old pointers need to be
+ // transferred to the old generation mark queues and the young pointers are NOT part
+ // of this snapshot, so they must be dropped here. It is safe to drop them here because
+ // we will rescan the roots on this safepoint.
+ heap->old_generation()->transfer_pointers_from_satb();
+ }
+
+ if (_degen_point == ShenandoahDegenPoint::_degenerated_roots) {
+ // We only need this if the concurrent cycle has already swapped the card tables.
+ // Marking will use the 'read' table, but interesting pointers may have been
+ // recorded in the 'write' table in the time between the cancelled concurrent cycle
+ // and this degenerated cycle. These pointers need to be included the 'read' table
+ // used to scan the remembered set during the STW mark which follows here.
+ _generation->merge_write_table();
+ }
+ }
op_reset();
// STW mark
op_mark();
// it, we fail degeneration right away and slide into Full GC to recover.
{
heap->sync_pinned_region_status();
heap->collection_set()->clear_current_index();
-
ShenandoahHeapRegion* r;
while ((r = heap->collection_set()->next()) != nullptr) {
if (r->is_pinned()) {
heap->cancel_gc(GCCause::_shenandoah_upgrade_to_full_gc);
op_degenerated_fail();
op_evacuate();
if (heap->cancelled_gc()) {
op_degenerated_fail();
return;
}
+ } else if (has_in_place_promotions(heap)) {
+ // We have nothing to evacuate, but there are still regions to promote in place.
+ ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_promote_regions);
+ ShenandoahGenerationalHeap::heap()->promote_regions_in_place(false /* concurrent*/);
}
+ // Update collector state regardless of whether there are forwarded objects
+ heap->set_evacuation_in_progress(false);
+ heap->set_concurrent_weak_root_in_progress(false);
+ heap->set_concurrent_strong_root_in_progress(false);
+
// If heuristics thinks we should do the cycle, this flag would be set,
// and we need to do update-refs. Otherwise, it would be the shortcut cycle.
if (heap->has_forwarded_objects()) {
op_init_updaterefs();
assert(!heap->cancelled_gc(), "STW reference update can not OOM");
+ } else {
+ _abbreviated = true;
}
case _degenerated_updaterefs:
if (heap->has_forwarded_objects()) {
op_updaterefs();
// Disarm nmethods that armed in concurrent cycle.
// In above case, update roots should disarm them
ShenandoahCodeRoots::disarm_nmethods();
op_cleanup_complete();
+
+ if (heap->mode()->is_generational()) {
+ ShenandoahGenerationalHeap::heap()->complete_degenerated_cycle();
+ }
+
break;
default:
ShouldNotReachHere();
}
metrics.snap_after();
// Check for futility and fail. There is no reason to do several back-to-back Degenerated cycles,
// because that probably means the heap is overloaded and/or fragmented.
if (!metrics.is_good_progress()) {
- heap->notify_gc_no_progress();
heap->cancel_gc(GCCause::_shenandoah_upgrade_to_full_gc);
op_degenerated_futile();
} else {
heap->notify_gc_progress();
}
}
void ShenandoahDegenGC::op_reset() {
! ShenandoahHeap::heap()->prepare_gc();
}
void ShenandoahDegenGC::op_mark() {
! assert(!ShenandoahHeap::heap()->is_concurrent_mark_in_progress(), "Should be reset");
ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_stw_mark);
! ShenandoahSTWMark mark(false /*full gc*/);
- mark.clear();
mark.mark();
}
void ShenandoahDegenGC::op_finish_mark() {
! ShenandoahConcurrentMark mark;
mark.finish_mark();
}
void ShenandoahDegenGC::op_prepare_evacuation() {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
metrics.snap_after();
// Check for futility and fail. There is no reason to do several back-to-back Degenerated cycles,
// because that probably means the heap is overloaded and/or fragmented.
if (!metrics.is_good_progress()) {
heap->cancel_gc(GCCause::_shenandoah_upgrade_to_full_gc);
op_degenerated_futile();
} else {
heap->notify_gc_progress();
+ heap->shenandoah_policy()->record_success_degenerated(_generation->is_young(), _abbreviated);
+ _generation->heuristics()->record_success_degenerated();
}
}
void ShenandoahDegenGC::op_reset() {
! _generation->prepare_gc();
}
void ShenandoahDegenGC::op_mark() {
! assert(!_generation->is_concurrent_mark_in_progress(), "Should be reset");
ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_stw_mark);
! ShenandoahSTWMark mark(_generation, false /*full gc*/);
mark.mark();
}
void ShenandoahDegenGC::op_finish_mark() {
! ShenandoahConcurrentMark mark(_generation);
mark.finish_mark();
}
void ShenandoahDegenGC::op_prepare_evacuation() {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
heap->verifier()->verify_roots_no_forwarded();
}
// STW cleanup weak roots and unload classes
heap->parallel_cleaning(false /*full gc*/);
// Prepare regions and collection set
! heap->prepare_regions_and_collection_set(false /*concurrent*/);
// Retire the TLABs, which will force threads to reacquire their TLABs after the pause.
// This is needed for two reasons. Strong one: new allocations would be with new freeset,
// which would be outside the collection set, so no cset writes would happen there.
// Weaker one: new allocations would happen past update watermark, and so less work would
heap->verifier()->verify_roots_no_forwarded();
}
// STW cleanup weak roots and unload classes
heap->parallel_cleaning(false /*full gc*/);
+
// Prepare regions and collection set
! _generation->prepare_regions_and_collection_set(false /*concurrent*/);
// Retire the TLABs, which will force threads to reacquire their TLABs after the pause.
// This is needed for two reasons. Strong one: new allocations would be with new freeset,
// which would be outside the collection set, so no cset writes would happen there.
// Weaker one: new allocations would happen past update watermark, and so less work would
ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_final_manage_labs);
heap->tlabs_retire(false);
}
if (!heap->collection_set()->is_empty()) {
heap->set_evacuation_in_progress(true);
- heap->set_has_forwarded_objects(true);
! if(ShenandoahVerify) {
- heap->verifier()->verify_during_evacuation();
- }
} else {
if (ShenandoahVerify) {
! heap->verifier()->verify_after_concmark();
}
if (VerifyAfterGC) {
Universe::verify();
}
}
}
void ShenandoahDegenGC::op_cleanup_early() {
ShenandoahHeap::heap()->recycle_trash();
}
void ShenandoahDegenGC::op_evacuate() {
ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_final_manage_labs);
heap->tlabs_retire(false);
}
if (!heap->collection_set()->is_empty()) {
+ if (ShenandoahVerify) {
+ heap->verifier()->verify_before_evacuation();
+ }
+
heap->set_evacuation_in_progress(true);
! heap->set_has_forwarded_objects(true);
} else {
if (ShenandoahVerify) {
! if (has_in_place_promotions(heap)) {
+ heap->verifier()->verify_after_concmark_with_promotions();
+ } else {
+ heap->verifier()->verify_after_concmark();
+ }
}
if (VerifyAfterGC) {
Universe::verify();
}
}
}
+ bool ShenandoahDegenGC::has_in_place_promotions(const ShenandoahHeap* heap) const {
+ return heap->mode()->is_generational() && heap->old_generation()->has_in_place_promotions();
+ }
+
void ShenandoahDegenGC::op_cleanup_early() {
ShenandoahHeap::heap()->recycle_trash();
}
void ShenandoahDegenGC::op_evacuate() {
}
void ShenandoahDegenGC::op_init_updaterefs() {
// Evacuation has completed
ShenandoahHeap* const heap = ShenandoahHeap::heap();
- heap->set_evacuation_in_progress(false);
- heap->set_concurrent_weak_root_in_progress(false);
- heap->set_concurrent_strong_root_in_progress(false);
-
heap->prepare_update_heap_references(false /*concurrent*/);
heap->set_update_refs_in_progress(true);
}
void ShenandoahDegenGC::op_updaterefs() {
ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_cleanup_complete);
ShenandoahHeap::heap()->recycle_trash();
}
void ShenandoahDegenGC::op_degenerated_fail() {
! log_info(gc)("Cannot finish degeneration, upgrading to Full GC");
- ShenandoahHeap::heap()->shenandoah_policy()->record_degenerated_upgrade_to_full();
-
- ShenandoahFullGC full_gc;
- full_gc.op_full(GCCause::_shenandoah_upgrade_to_full_gc);
}
void ShenandoahDegenGC::op_degenerated_futile() {
! ShenandoahHeap::heap()->shenandoah_policy()->record_degenerated_upgrade_to_full();
- ShenandoahFullGC full_gc;
- full_gc.op_full(GCCause::_shenandoah_upgrade_to_full_gc);
}
const char* ShenandoahDegenGC::degen_event_message(ShenandoahDegenPoint point) const {
switch (point) {
case _degenerated_unset:
! return "Pause Degenerated GC (<UNSET>)";
case _degenerated_outside_cycle:
! return "Pause Degenerated GC (Outside of Cycle)";
case _degenerated_mark:
! return "Pause Degenerated GC (Mark)";
case _degenerated_evac:
! return "Pause Degenerated GC (Evacuation)";
case _degenerated_updaterefs:
! return "Pause Degenerated GC (Update Refs)";
default:
ShouldNotReachHere();
! return "ERROR";
}
}
ShenandoahGCPhase phase(ShenandoahPhaseTimings::degen_gc_cleanup_complete);
ShenandoahHeap::heap()->recycle_trash();
}
void ShenandoahDegenGC::op_degenerated_fail() {
! upgrade_to_full();
}
void ShenandoahDegenGC::op_degenerated_futile() {
! upgrade_to_full();
}
const char* ShenandoahDegenGC::degen_event_message(ShenandoahDegenPoint point) const {
switch (point) {
case _degenerated_unset:
! SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Pause Degenerated GC", " (<UNSET>)");
case _degenerated_outside_cycle:
! SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Pause Degenerated GC", " (Outside of Cycle)");
+ case _degenerated_roots:
+ SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Pause Degenerated GC", " (Roots)");
case _degenerated_mark:
! SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Pause Degenerated GC", " (Mark)");
case _degenerated_evac:
! SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Pause Degenerated GC", " (Evacuation)");
case _degenerated_updaterefs:
! SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Pause Degenerated GC", " (Update Refs)");
default:
ShouldNotReachHere();
! SHENANDOAH_RETURN_EVENT_MESSAGE(_generation->type(), "Pause Degenerated GC", " (?)");
}
}
+
+ void ShenandoahDegenGC::upgrade_to_full() {
+ log_info(gc)("Degenerated GC upgrading to Full GC");
+ ShenandoahHeap::heap()->shenandoah_policy()->record_degenerated_upgrade_to_full();
+ ShenandoahFullGC full_gc;
+ full_gc.op_full(GCCause::_shenandoah_upgrade_to_full_gc);
+ }
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