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/*
* Copyright (c) 2021, 2022, 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/continuationGCSupport.inline.hpp"
#include "gc/shenandoah/shenandoahBreakpoint.hpp"
#include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
#include "gc/shenandoah/shenandoahConcurrentGC.hpp"
#include "gc/shenandoah/shenandoahFreeSet.hpp"
+ #include "gc/shenandoah/shenandoahGeneration.hpp"
+ #include "gc/shenandoah/shenandoahOldGeneration.hpp"
+ #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
#include "gc/shenandoah/shenandoahLock.hpp"
#include "gc/shenandoah/shenandoahMark.inline.hpp"
#include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
#include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
#include "gc/shenandoah/shenandoahPhaseTimings.hpp"
ShenandoahBreakpoint::at_before_marking_completed();
}
}
};
! ShenandoahConcurrentGC::ShenandoahConcurrentGC() :
! _mark(),
! _degen_point(ShenandoahDegenPoint::_degenerated_unset) {
}
ShenandoahGC::ShenandoahDegenPoint ShenandoahConcurrentGC::degen_point() const {
return _degen_point;
}
- void ShenandoahConcurrentGC::cancel() {
- ShenandoahConcurrentMark::cancel();
- }
-
bool ShenandoahConcurrentGC::collect(GCCause::Cause cause) {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
ShenandoahBreakpointGCScope breakpoint_gc_scope(cause);
// Reset for upcoming marking
entry_reset();
// Start initial mark under STW
vmop_entry_init_mark();
{
ShenandoahBreakpointMarkScope breakpoint_mark_scope(cause);
// Concurrent mark roots
entry_mark_roots();
! if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_outside_cycle)) return false;
// Continue concurrent mark
entry_mark();
! if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_mark)) return false;
}
// Complete marking under STW, and start evacuation
vmop_entry_final_mark();
// Concurrent stack processing
if (heap->is_evacuation_in_progress()) {
entry_thread_roots();
}
ShenandoahBreakpoint::at_before_marking_completed();
}
}
};
! ShenandoahConcurrentGC::ShenandoahConcurrentGC(ShenandoahGeneration* generation, bool do_old_gc_bootstrap) :
! _mark(generation),
! _degen_point(ShenandoahDegenPoint::_degenerated_unset),
+ _abbreviated(false),
+ _do_old_gc_bootstrap(do_old_gc_bootstrap),
+ _generation(generation) {
}
ShenandoahGC::ShenandoahDegenPoint ShenandoahConcurrentGC::degen_point() const {
return _degen_point;
}
bool ShenandoahConcurrentGC::collect(GCCause::Cause cause) {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
+ heap->start_conc_gc();
+
ShenandoahBreakpointGCScope breakpoint_gc_scope(cause);
// Reset for upcoming marking
entry_reset();
// Start initial mark under STW
vmop_entry_init_mark();
{
ShenandoahBreakpointMarkScope breakpoint_mark_scope(cause);
+
+ // Reset task queue stats here, rather than in mark_concurrent_roots,
+ // because remembered set scan will `push` oops into the queues and
+ // resetting after this happens will lose those counts.
+ TASKQUEUE_STATS_ONLY(_mark.task_queues()->reset_taskqueue_stats());
+
+ // Concurrent remembered set scanning
+ entry_scan_remembered_set();
+ // TODO: When RS scanning yields, we will need a check_cancellation_and_abort() degeneration point here.
+
// Concurrent mark roots
entry_mark_roots();
! if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_roots)) {
+ return false;
+ }
// Continue concurrent mark
entry_mark();
! if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_mark)) {
+ return false;
+ }
}
// Complete marking under STW, and start evacuation
vmop_entry_final_mark();
+ // If GC was cancelled before final mark, then the safepoint operation will do nothing
+ // and the concurrent mark will still be in progress. In this case it is safe to resume
+ // the degenerated cycle from the marking phase. On the other hand, if the GC is cancelled
+ // after final mark (but before this check), then the final mark safepoint operation
+ // will have finished the mark (setting concurrent mark in progress to false). Final mark
+ // will also have setup state (in concurrent stack processing) that will not be safe to
+ // resume from the marking phase in the degenerated cycle. That is, if the cancellation
+ // occurred after final mark, we must resume the degenerated cycle after the marking phase.
+ if (_generation->is_concurrent_mark_in_progress() && check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_mark)) {
+ assert(!heap->is_concurrent_weak_root_in_progress(), "Weak roots should not be in progress when concurrent mark is in progress");
+ return false;
+ }
+
// Concurrent stack processing
if (heap->is_evacuation_in_progress()) {
entry_thread_roots();
}
entry_weak_refs();
entry_weak_roots();
}
// Final mark might have reclaimed some immediate garbage, kick cleanup to reclaim
! // the space. This would be the last action if there is nothing to evacuate.
entry_cleanup_early();
{
ShenandoahHeapLocker locker(heap->lock());
heap->free_set()->log_status();
entry_weak_refs();
entry_weak_roots();
}
// Final mark might have reclaimed some immediate garbage, kick cleanup to reclaim
! // the space. This would be the last action if there is nothing to evacuate. Note that
+ // we will not age young-gen objects in the case that we skip evacuation.
entry_cleanup_early();
{
ShenandoahHeapLocker locker(heap->lock());
heap->free_set()->log_status();
// This may be skipped if there is nothing to evacuate.
// If so, evac_in_progress would be unset by collection set preparation code.
if (heap->is_evacuation_in_progress()) {
// Concurrently evacuate
entry_evacuate();
! if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_evac)) return false;
// Perform update-refs phase.
vmop_entry_init_updaterefs();
entry_updaterefs();
! if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_updaterefs)) return false;
// Concurrent update thread roots
entry_update_thread_roots();
! if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_updaterefs)) return false;
vmop_entry_final_updaterefs();
// Update references freed up collection set, kick the cleanup to reclaim the space.
entry_cleanup_complete();
} else {
vmop_entry_final_roots();
}
return true;
}
void ShenandoahConcurrentGC::vmop_entry_init_mark() {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
// This may be skipped if there is nothing to evacuate.
// If so, evac_in_progress would be unset by collection set preparation code.
if (heap->is_evacuation_in_progress()) {
// Concurrently evacuate
entry_evacuate();
! if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_evac)) {
+ return false;
+ }
+ }
+ if (heap->has_forwarded_objects()) {
// Perform update-refs phase.
vmop_entry_init_updaterefs();
entry_updaterefs();
! if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_updaterefs)) {
+ return false;
+ }
// Concurrent update thread roots
entry_update_thread_roots();
! if (check_cancellation_and_abort(ShenandoahDegenPoint::_degenerated_updaterefs)) {
+ return false;
+ }
vmop_entry_final_updaterefs();
// Update references freed up collection set, kick the cleanup to reclaim the space.
entry_cleanup_complete();
} else {
+ // We chose not to evacuate because we found sufficient immediate garbage. Note that we
+ // do not check for cancellation here because, at this point, the cycle is effectively
+ // complete. If the cycle has been cancelled here, the control thread will detect it
+ // on its next iteration and run a degenerated young cycle.
vmop_entry_final_roots();
+ _abbreviated = true;
}
+ // We defer generation resizing actions until after cset regions have been recycled. We do this even following an
+ // abbreviated cycle.
+ if (heap->mode()->is_generational()) {
+ bool success;
+ size_t region_xfer;
+ const char* region_destination;
+ ShenandoahYoungGeneration* young_gen = heap->young_generation();
+ ShenandoahGeneration* old_gen = heap->old_generation();
+ {
+ ShenandoahHeapLocker locker(heap->lock());
+
+ size_t old_region_surplus = heap->get_old_region_surplus();
+ size_t old_region_deficit = heap->get_old_region_deficit();
+ if (old_region_surplus) {
+ success = heap->generation_sizer()->transfer_to_young(old_region_surplus);
+ region_destination = "young";
+ region_xfer = old_region_surplus;
+ } else if (old_region_deficit) {
+ success = heap->generation_sizer()->transfer_to_old(old_region_deficit);
+ region_destination = "old";
+ region_xfer = old_region_deficit;
+ if (!success) {
+ ((ShenandoahOldHeuristics *) old_gen->heuristics())->trigger_cannot_expand();
+ }
+ } else {
+ region_destination = "none";
+ region_xfer = 0;
+ success = true;
+ }
+ heap->set_old_region_surplus(0);
+ heap->set_old_region_deficit(0);
+
+ size_t old_usage_before_evac = heap->capture_old_usage(0);
+ size_t old_usage_now = old_gen->used();
+ size_t promoted_bytes = old_usage_now - old_usage_before_evac;
+ heap->set_previous_promotion(promoted_bytes);
+ heap->set_young_evac_reserve(0);
+ heap->set_old_evac_reserve(0);
+ heap->reset_old_evac_expended();
+ heap->set_promoted_reserve(0);
+ }
+
+ // Report outside the heap lock
+ size_t young_available = young_gen->available();
+ size_t old_available = old_gen->available();
+ log_info(gc, ergo)("After cleanup, %s " SIZE_FORMAT " regions to %s to prepare for next gc, old available: "
+ SIZE_FORMAT "%s, young_available: " SIZE_FORMAT "%s",
+ success? "successfully transferred": "failed to transfer", region_xfer, region_destination,
+ byte_size_in_proper_unit(old_available), proper_unit_for_byte_size(old_available),
+ byte_size_in_proper_unit(young_available), proper_unit_for_byte_size(young_available));
+ }
return true;
}
void ShenandoahConcurrentGC::vmop_entry_init_mark() {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
heap->try_inject_alloc_failure();
op_reset();
}
+ void ShenandoahConcurrentGC::entry_scan_remembered_set() {
+ if (_generation->is_young()) {
+ ShenandoahHeap* const heap = ShenandoahHeap::heap();
+ TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
+ const char* msg = "Concurrent remembered set scanning";
+ ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::init_scan_rset);
+ EventMark em("%s", msg);
+
+ ShenandoahWorkerScope scope(heap->workers(),
+ ShenandoahWorkerPolicy::calc_workers_for_rs_scanning(),
+ msg);
+
+ heap->try_inject_alloc_failure();
+ _generation->scan_remembered_set(true /* is_concurrent */);
+ }
+ }
+
void ShenandoahConcurrentGC::entry_mark_roots() {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
const char* msg = "Concurrent marking roots";
ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_mark_roots);
void ShenandoahConcurrentGC::op_reset() {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
if (ShenandoahPacing) {
heap->pacer()->setup_for_reset();
}
!
- heap->prepare_gc();
}
class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
private:
ShenandoahMarkingContext* const _ctx;
void ShenandoahConcurrentGC::op_reset() {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
if (ShenandoahPacing) {
heap->pacer()->setup_for_reset();
}
! _generation->prepare_gc();
}
class ShenandoahInitMarkUpdateRegionStateClosure : public ShenandoahHeapRegionClosure {
private:
ShenandoahMarkingContext* const _ctx;
void heap_region_do(ShenandoahHeapRegion* r) {
assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
if (r->is_active()) {
// Check if region needs updating its TAMS. We have updated it already during concurrent
! // reset, so it is very likely we don't need to do another write here.
if (_ctx->top_at_mark_start(r) != r->top()) {
_ctx->capture_top_at_mark_start(r);
}
} else {
assert(_ctx->top_at_mark_start(r) == r->top(),
void heap_region_do(ShenandoahHeapRegion* r) {
assert(!r->has_live(), "Region " SIZE_FORMAT " should have no live data", r->index());
if (r->is_active()) {
// Check if region needs updating its TAMS. We have updated it already during concurrent
! // reset, so it is very likely we don't need to do another write here. Since most regions
+ // are not "active", this path is relatively rare.
if (_ctx->top_at_mark_start(r) != r->top()) {
_ctx->capture_top_at_mark_start(r);
}
} else {
assert(_ctx->top_at_mark_start(r) == r->top(),
void ShenandoahConcurrentGC::op_init_mark() {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
! assert(heap->marking_context()->is_bitmap_clear(), "need clear marking bitmap");
! assert(!heap->marking_context()->is_complete(), "should not be complete");
assert(!heap->has_forwarded_objects(), "No forwarded objects on this path");
if (ShenandoahVerify) {
heap->verifier()->verify_before_concmark();
}
if (VerifyBeforeGC) {
Universe::verify();
}
! heap->set_concurrent_mark_in_progress(true);
start_mark();
! {
ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_region_states);
ShenandoahInitMarkUpdateRegionStateClosure cl;
heap->parallel_heap_region_iterate(&cl);
}
// Weak reference processing
! ShenandoahReferenceProcessor* rp = heap->ref_processor();
rp->reset_thread_locals();
rp->set_soft_reference_policy(heap->soft_ref_policy()->should_clear_all_soft_refs());
// Make above changes visible to worker threads
OrderAccess::fence();
void ShenandoahConcurrentGC::op_init_mark() {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Should be at safepoint");
assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
! assert(_generation->is_bitmap_clear(), "need clear marking bitmap");
! assert(!_generation->is_mark_complete(), "should not be complete");
assert(!heap->has_forwarded_objects(), "No forwarded objects on this path");
+
+ if (heap->mode()->is_generational()) {
+ if (_generation->is_young() || (_generation->is_global() && ShenandoahVerify)) {
+ // The current implementation of swap_remembered_set() copies the write-card-table
+ // to the read-card-table. The remembered sets are also swapped for GLOBAL collections
+ // so that the verifier works with the correct copy of the card table when verifying.
+ // TODO: This path should not really depend on ShenandoahVerify.
+ ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_swap_rset);
+ _generation->swap_remembered_set();
+ }
+
+ if (_generation->is_global()) {
+ heap->cancel_old_gc();
+ } else if (heap->is_concurrent_old_mark_in_progress()) {
+ // Purge the SATB buffers, transferring any valid, old pointers to the
+ // old generation mark queue. Any pointers in a young region will be
+ // abandoned.
+ ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_transfer_satb);
+ heap->transfer_old_pointers_from_satb();
+ }
+ }
+
if (ShenandoahVerify) {
heap->verifier()->verify_before_concmark();
}
if (VerifyBeforeGC) {
Universe::verify();
}
! _generation->set_concurrent_mark_in_progress(true);
start_mark();
! if (_do_old_gc_bootstrap) {
+ // Update region state for both young and old regions
+ // TODO: We should be able to pull this out of the safepoint for the bootstrap
+ // cycle. The top of an old region will only move when a GC cycle evacuates
+ // objects into it. When we start an old cycle, we know that nothing can touch
+ // the top of old regions.
ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_region_states);
ShenandoahInitMarkUpdateRegionStateClosure cl;
heap->parallel_heap_region_iterate(&cl);
+ } else {
+ // Update region state for only young regions
+ ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_region_states);
+ ShenandoahInitMarkUpdateRegionStateClosure cl;
+ _generation->parallel_heap_region_iterate(&cl);
}
// Weak reference processing
! ShenandoahReferenceProcessor* rp = _generation->ref_processor();
rp->reset_thread_locals();
rp->set_soft_reference_policy(heap->soft_ref_policy()->should_clear_all_soft_refs());
// Make above changes visible to worker threads
OrderAccess::fence();
assert(!heap->cancelled_gc(), "STW mark cannot OOM");
// Notify JVMTI that the tagmap table will need cleaning.
JvmtiTagMap::set_needs_cleaning();
! heap->prepare_regions_and_collection_set(true /*concurrent*/);
// Has to be done after cset selection
heap->prepare_concurrent_roots();
! if (!heap->collection_set()->is_empty()) {
! if (ShenandoahVerify) {
! heap->verifier()->verify_before_evacuation();
! }
!
! heap->set_evacuation_in_progress(true);
! // From here on, we need to update references.
! heap->set_has_forwarded_objects(true);
!
! // Verify before arming for concurrent processing.
! // Otherwise, verification can trigger stack processing.
! if (ShenandoahVerify) {
! heap->verifier()->verify_during_evacuation();
! }
!
! // Arm nmethods/stack for concurrent processing
! ShenandoahCodeRoots::arm_nmethods_for_evac();
! ShenandoahStackWatermark::change_epoch_id();
!
! if (ShenandoahPacing) {
! heap->pacer()->setup_for_evac();
}
} else {
! if (ShenandoahVerify) {
! heap->verifier()->verify_after_concmark();
! }
!
! if (VerifyAfterGC) {
! Universe::verify();
}
}
}
}
assert(!heap->cancelled_gc(), "STW mark cannot OOM");
// Notify JVMTI that the tagmap table will need cleaning.
JvmtiTagMap::set_needs_cleaning();
! // The collection set is chosen by prepare_regions_and_collection_set().
+ //
+ // TODO: Under severe memory overload conditions that can be checked here, we may want to limit
+ // the inclusion of old-gen candidates within the collection set. This would allow us to prioritize efforts on
+ // evacuating young-gen, This remediation is most appropriate when old-gen availability is very high (so there
+ // are negligible negative impacts from delaying completion of old-gen evacuation) and when young-gen collections
+ // are "under duress" (as signalled by very low availability of memory within young-gen, indicating that/ young-gen
+ // collections are not triggering frequently enough).
+ _generation->prepare_regions_and_collection_set(true /*concurrent*/);
+
+ // Upon return from prepare_regions_and_collection_set(), certain parameters have been established to govern the
+ // evacuation efforts that are about to begin. In particular:
+ //
+ // heap->get_promoted_reserve() represents the amount of memory within old-gen's available memory that has
+ // been set aside to hold objects promoted from young-gen memory. This represents an estimated percentage
+ // of the live young-gen memory within the collection set. If there is more data ready to be promoted than
+ // can fit within this reserve, the promotion of some objects will be deferred until a subsequent evacuation
+ // pass.
+ //
+ // heap->get_old_evac_reserve() represents the amount of memory within old-gen's available memory that has been
+ // set aside to hold objects evacuated from the old-gen collection set.
+ //
+ // heap->get_young_evac_reserve() represents the amount of memory within young-gen's available memory that has
+ // been set aside to hold objects evacuated from the young-gen collection set. Conservatively, this value
+ // equals the entire amount of live young-gen memory within the collection set, even though some of this memory
+ // will likely be promoted.
// Has to be done after cset selection
heap->prepare_concurrent_roots();
! if (heap->mode()->is_generational()) {
! size_t humongous_regions_promoted = heap->get_promotable_humongous_regions();
! size_t regular_regions_promoted_in_place = heap->get_regular_regions_promoted_in_place();
! if (!heap->collection_set()->is_empty() || (humongous_regions_promoted + regular_regions_promoted_in_place > 0)) {
! // Even if the collection set is empty, we need to do evacuation if there are regions to be promoted in place.
! // Concurrent evacuation takes responsibility for registering objects and setting the remembered set cards to dirty.
!
! LogTarget(Debug, gc, cset) lt;
! if (lt.is_enabled()) {
! ResourceMark rm;
! LogStream ls(lt);
! heap->collection_set()->print_on(&ls);
! }
!
! if (ShenandoahVerify) {
! heap->verifier()->verify_before_evacuation();
! }
!
! heap->set_evacuation_in_progress(true);
!
! // Verify before arming for concurrent processing.
+ // Otherwise, verification can trigger stack processing.
+ if (ShenandoahVerify) {
+ heap->verifier()->verify_during_evacuation();
+ }
+
+ // Generational mode may promote objects in place during the evacuation phase.
+ // If that is the only reason we are evacuating, we don't need to update references
+ // and there will be no forwarded objects on the heap.
+ heap->set_has_forwarded_objects(!heap->collection_set()->is_empty());
+
+ // Arm nmethods/stack for concurrent processing
+ if (!heap->collection_set()->is_empty()) {
+ // Iff objects will be evaluated, arm the nmethod barriers. These will be disarmed
+ // under the same condition (established in prepare_concurrent_roots) after strong
+ // root evacuation has completed (see op_strong_roots).
+ ShenandoahCodeRoots::arm_nmethods_for_evac();
+ ShenandoahStackWatermark::change_epoch_id();
+ }
+
+ if (ShenandoahPacing) {
+ heap->pacer()->setup_for_evac();
+ }
+ } else {
+ if (ShenandoahVerify) {
+ heap->verifier()->verify_after_concmark();
+ }
+
+ if (VerifyAfterGC) {
+ Universe::verify();
+ }
}
} else {
! // Not is_generational()
! if (!heap->collection_set()->is_empty()) {
! LogTarget(Info, gc, ergo) lt;
! if (lt.is_enabled()) {
! ResourceMark rm;
! LogStream ls(lt);
+ heap->collection_set()->print_on(&ls);
+ }
+
+ if (ShenandoahVerify) {
+ heap->verifier()->verify_before_evacuation();
+ }
+
+ heap->set_evacuation_in_progress(true);
+
+ // Verify before arming for concurrent processing.
+ // Otherwise, verification can trigger stack processing.
+ if (ShenandoahVerify) {
+ heap->verifier()->verify_during_evacuation();
+ }
+
+ // From here on, we need to update references.
+ heap->set_has_forwarded_objects(true);
+
+ // Arm nmethods/stack for concurrent processing
+ ShenandoahCodeRoots::arm_nmethods_for_evac();
+ ShenandoahStackWatermark::change_epoch_id();
+
+ if (ShenandoahPacing) {
+ heap->pacer()->setup_for_evac();
+ }
+ } else {
+ if (ShenandoahVerify) {
+ heap->verifier()->verify_after_concmark();
+ }
+
+ if (VerifyAfterGC) {
+ Universe::verify();
+ }
}
}
}
}
}
void ShenandoahConcurrentEvacThreadClosure::do_thread(Thread* thread) {
JavaThread* const jt = JavaThread::cast(thread);
StackWatermarkSet::finish_processing(jt, _oops, StackWatermarkKind::gc);
+ ShenandoahThreadLocalData::enable_plab_promotions(thread);
}
class ShenandoahConcurrentEvacUpdateThreadTask : public WorkerTask {
private:
ShenandoahJavaThreadsIterator _java_threads;
WorkerTask("Shenandoah Evacuate/Update Concurrent Thread Roots"),
_java_threads(ShenandoahPhaseTimings::conc_thread_roots, n_workers) {
}
void work(uint worker_id) {
+ Thread* worker_thread = Thread::current();
+ ShenandoahThreadLocalData::enable_plab_promotions(worker_thread);
+
// ShenandoahEvacOOMScope has to be setup by ShenandoahContextEvacuateUpdateRootsClosure.
// Otherwise, may deadlock with watermark lock
ShenandoahContextEvacuateUpdateRootsClosure oops_cl;
ShenandoahConcurrentEvacThreadClosure thr_cl(&oops_cl);
_java_threads.threads_do(&thr_cl, worker_id);
// Concurrent weak refs processing
ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_weak_refs);
if (heap->gc_cause() == GCCause::_wb_breakpoint) {
ShenandoahBreakpoint::at_after_reference_processing_started();
}
! heap->ref_processor()->process_references(ShenandoahPhaseTimings::conc_weak_refs, heap->workers(), true /* concurrent */);
}
class ShenandoahEvacUpdateCleanupOopStorageRootsClosure : public BasicOopIterateClosure {
private:
ShenandoahHeap* const _heap;
// Concurrent weak refs processing
ShenandoahGCWorkerPhase worker_phase(ShenandoahPhaseTimings::conc_weak_refs);
if (heap->gc_cause() == GCCause::_wb_breakpoint) {
ShenandoahBreakpoint::at_after_reference_processing_started();
}
! _generation->ref_processor()->process_references(ShenandoahPhaseTimings::conc_weak_refs, heap->workers(), true /* concurrent */);
}
class ShenandoahEvacUpdateCleanupOopStorageRootsClosure : public BasicOopIterateClosure {
private:
ShenandoahHeap* const _heap;
void ShenandoahEvacUpdateCleanupOopStorageRootsClosure::do_oop(oop* p) {
const oop obj = RawAccess<>::oop_load(p);
if (!CompressedOops::is_null(obj)) {
if (!_mark_context->is_marked(obj)) {
! shenandoah_assert_correct(p, obj);
! ShenandoahHeap::atomic_clear_oop(p, obj);
} else if (_evac_in_progress && _heap->in_collection_set(obj)) {
oop resolved = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
if (resolved == obj) {
resolved = _heap->evacuate_object(obj, _thread);
}
void ShenandoahEvacUpdateCleanupOopStorageRootsClosure::do_oop(oop* p) {
const oop obj = RawAccess<>::oop_load(p);
if (!CompressedOops::is_null(obj)) {
if (!_mark_context->is_marked(obj)) {
! if (_heap->is_in_active_generation(obj)) {
! // TODO: This worries me. Here we are asserting that an unmarked from-space object is 'correct'.
+ // Normally, I would call this a bogus assert, but there seems to be a legitimate use-case for
+ // accessing from-space objects during class unloading. However, the from-space object may have
+ // been "filled". We've made no effort to prevent old generation classes being unloaded by young
+ // gen (and vice-versa).
+ shenandoah_assert_correct(p, obj);
+ ShenandoahHeap::atomic_clear_oop(p, obj);
+ }
} else if (_evac_in_progress && _heap->in_collection_set(obj)) {
oop resolved = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
if (resolved == obj) {
resolved = _heap->evacuate_object(obj, _thread);
}
ShenandoahHeap* const heap = ShenandoahHeap::heap();
heap->set_evacuation_in_progress(false);
heap->set_concurrent_weak_root_in_progress(false);
heap->prepare_update_heap_references(true /*concurrent*/);
heap->set_update_refs_in_progress(true);
!
if (ShenandoahPacing) {
heap->pacer()->setup_for_updaterefs();
}
}
ShenandoahHeap* const heap = ShenandoahHeap::heap();
heap->set_evacuation_in_progress(false);
heap->set_concurrent_weak_root_in_progress(false);
heap->prepare_update_heap_references(true /*concurrent*/);
heap->set_update_refs_in_progress(true);
! if (ShenandoahVerify) {
+ heap->verifier()->verify_before_updaterefs();
+ }
if (ShenandoahPacing) {
heap->pacer()->setup_for_updaterefs();
}
}
heap->finish_concurrent_roots();
// Clear cancelled GC, if set. On cancellation path, the block before would handle
// everything.
if (heap->cancelled_gc()) {
! heap->clear_cancelled_gc();
}
// Has to be done before cset is clear
if (ShenandoahVerify) {
heap->verifier()->verify_roots_in_to_space();
}
heap->update_heap_region_states(true /*concurrent*/);
heap->set_update_refs_in_progress(false);
heap->set_has_forwarded_objects(false);
if (ShenandoahVerify) {
heap->verifier()->verify_after_updaterefs();
}
if (VerifyAfterGC) {
heap->finish_concurrent_roots();
// Clear cancelled GC, if set. On cancellation path, the block before would handle
// everything.
if (heap->cancelled_gc()) {
! heap->clear_cancelled_gc(true /* clear oom handler */);
}
// Has to be done before cset is clear
if (ShenandoahVerify) {
heap->verifier()->verify_roots_in_to_space();
}
+ if (heap->mode()->is_generational() && heap->is_concurrent_old_mark_in_progress()) {
+ // When the SATB barrier is left on to support concurrent old gen mark, it may pick up writes to
+ // objects in the collection set. After those objects are evacuated, the pointers in the
+ // SATB are no longer safe. Once we have finished update references, we are guaranteed that
+ // no more writes to the collection set are possible.
+ //
+ // This will transfer any old pointers in _active_ regions from the SATB to the old gen
+ // mark queues. All other pointers will be discarded. This would also discard any pointers
+ // in old regions that were included in a mixed evacuation. We aren't using the SATB filter
+ // methods here because we cannot control when they execute. If the SATB filter runs _after_
+ // a region has been recycled, we will not be able to detect the bad pointer.
+ //
+ // We are not concerned about skipping this step in abbreviated cycles because regions
+ // with no live objects cannot have been written to and so cannot have entries in the SATB
+ // buffers.
+ heap->transfer_old_pointers_from_satb();
+ }
+
heap->update_heap_region_states(true /*concurrent*/);
heap->set_update_refs_in_progress(false);
heap->set_has_forwarded_objects(false);
+ // Aging_cycle is only relevant during evacuation cycle for individual objects and during final mark for
+ // entire regions. Both of these relevant operations occur before final update refs.
+ heap->set_aging_cycle(false);
+
if (ShenandoahVerify) {
heap->verifier()->verify_after_updaterefs();
}
if (VerifyAfterGC) {
heap->rebuild_free_set(true /*concurrent*/);
}
void ShenandoahConcurrentGC::op_final_roots() {
! ShenandoahHeap::heap()->set_concurrent_weak_root_in_progress(false);
}
void ShenandoahConcurrentGC::op_cleanup_complete() {
ShenandoahHeap::heap()->free_set()->recycle_trash();
}
heap->rebuild_free_set(true /*concurrent*/);
}
void ShenandoahConcurrentGC::op_final_roots() {
!
+ ShenandoahHeap *heap = ShenandoahHeap::heap();
+ heap->set_concurrent_weak_root_in_progress(false);
+ heap->set_evacuation_in_progress(false);
+
+ if (heap->mode()->is_generational()) {
+ ShenandoahMarkingContext *ctx = heap->complete_marking_context();
+
+ for (size_t i = 0; i < heap->num_regions(); i++) {
+ ShenandoahHeapRegion *r = heap->get_region(i);
+ if (r->is_active() && r->is_young()) {
+ HeapWord* tams = ctx->top_at_mark_start(r);
+ HeapWord* top = r->top();
+ if (top > tams) {
+ r->reset_age();
+ } else if (heap->is_aging_cycle()) {
+ r->increment_age();
+ }
+ }
+ }
+ }
}
void ShenandoahConcurrentGC::op_cleanup_complete() {
ShenandoahHeap::heap()->free_set()->recycle_trash();
}
const char* ShenandoahConcurrentGC::init_mark_event_message() const {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
assert(!heap->has_forwarded_objects(), "Should not have forwarded objects here");
if (heap->unload_classes()) {
! return "Pause Init Mark (unload classes)";
} else {
! return "Pause Init Mark";
}
}
const char* ShenandoahConcurrentGC::final_mark_event_message() const {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
! assert(!heap->has_forwarded_objects(), "Should not have forwarded objects here");
if (heap->unload_classes()) {
! return "Pause Final Mark (unload classes)";
} else {
! return "Pause Final Mark";
}
}
const char* ShenandoahConcurrentGC::conc_mark_event_message() const {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
! assert(!heap->has_forwarded_objects(), "Should not have forwarded objects here");
if (heap->unload_classes()) {
! return "Concurrent marking (unload classes)";
} else {
! return "Concurrent marking";
}
}
const char* ShenandoahConcurrentGC::init_mark_event_message() const {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
assert(!heap->has_forwarded_objects(), "Should not have forwarded objects here");
if (heap->unload_classes()) {
! SHENANDOAH_RETURN_EVENT_MESSAGE(heap, _generation->type(), "Pause Init Mark", " (unload classes)");
} else {
! SHENANDOAH_RETURN_EVENT_MESSAGE(heap, _generation->type(), "Pause Init Mark", "");
}
}
const char* ShenandoahConcurrentGC::final_mark_event_message() const {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
! assert(!heap->has_forwarded_objects() || heap->is_concurrent_old_mark_in_progress(),
+ "Should not have forwarded objects during final mark, unless old gen concurrent mark is running");
+
if (heap->unload_classes()) {
! SHENANDOAH_RETURN_EVENT_MESSAGE(heap, _generation->type(), "Pause Final Mark", " (unload classes)");
} else {
! SHENANDOAH_RETURN_EVENT_MESSAGE(heap, _generation->type(), "Pause Final Mark", "");
}
}
const char* ShenandoahConcurrentGC::conc_mark_event_message() const {
ShenandoahHeap* const heap = ShenandoahHeap::heap();
! assert(!heap->has_forwarded_objects() || heap->is_concurrent_old_mark_in_progress(),
+ "Should not have forwarded objects concurrent mark, unless old gen concurrent mark is running");
if (heap->unload_classes()) {
! SHENANDOAH_RETURN_EVENT_MESSAGE(heap, _generation->type(), "Concurrent marking", " (unload classes)");
} else {
! SHENANDOAH_RETURN_EVENT_MESSAGE(heap, _generation->type(), "Concurrent marking", "");
}
}
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