/* * Copyright (c) 2001, 2022, Oracle and/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. * * 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. *
*/
void ReferenceProcessor::init_statics() { // We need a monotonically non-decreasing time in ms but // os::javaTimeMillis() does not guarantee monotonicity.
jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
// Initialize the soft ref timestamp clock.
_soft_ref_timestamp_clock = now; // Also update the soft ref clock in j.l.r.SoftReference
java_lang_ref_SoftReference::set_clock(_soft_ref_timestamp_clock);
_always_clear_soft_ref_policy = new AlwaysClearPolicy(); if (CompilerConfig::is_c2_or_jvmci_compiler_enabled()) {
_default_soft_ref_policy = new LRUMaxHeapPolicy();
} else {
_default_soft_ref_policy = new LRUCurrentHeapPolicy();
}
guarantee(RefDiscoveryPolicy == ReferenceBasedDiscovery ||
RefDiscoveryPolicy == ReferentBasedDiscovery, "Unrecognized RefDiscoveryPolicy");
}
void ReferenceProcessor::enable_discovery(bool check_no_refs) { #ifdef ASSERT // Verify that we're not currently discovering refs
assert(!_discovering_refs, "nested call?");
if (check_no_refs) { // Verify that the discovered lists are empty
verify_no_references_recorded();
} #endif// ASSERT
void ReferenceProcessor::weak_oops_do(OopClosure* f) { for (uint i = 0; i < _max_num_queues * number_of_subclasses_of_ref(); i++) { if (UseCompressedOops) {
f->do_oop((narrowOop*)_discovered_refs[i].adr_head());
} else {
f->do_oop((oop*)_discovered_refs[i].adr_head());
}
}
}
void ReferenceProcessor::update_soft_ref_master_clock() { // Update (advance) the soft ref master clock field. This must be done // after processing the soft ref list.
// We need a monotonically non-decreasing time in ms but // os::javaTimeMillis() does not guarantee monotonicity.
jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
NOT_PRODUCT( if (now < _soft_ref_timestamp_clock) {
log_warning(gc)("time warp: " JLONG_FORMAT " to " JLONG_FORMAT,
_soft_ref_timestamp_clock, now);
}
) // The values of now and _soft_ref_timestamp_clock are set using // javaTimeNanos(), which is guaranteed to be monotonically // non-decreasing provided the underlying platform provides such // a time source (and it is bug free). // In product mode, however, protect ourselves from non-monotonicity. if (now > _soft_ref_timestamp_clock) {
_soft_ref_timestamp_clock = now;
java_lang_ref_SoftReference::set_clock(now);
} // Else leave clock stalled at its old value until time progresses // past clock value.
}
size_t ReferenceProcessor::total_count(DiscoveredList lists[]) const {
size_t total = 0; for (uint i = 0; i < _max_num_queues; ++i) {
total += lists[i].length();
} return total;
}
#ifdef ASSERT void ReferenceProcessor::verify_total_count_zero(DiscoveredList lists[], constchar* type) {
size_t count = total_count(lists);
assert(count == 0, "%ss must be empty but has " SIZE_FORMAT " elements", type, count);
} #endif
void BarrierEnqueueDiscoveredFieldClosure::enqueue(HeapWord* discovered_field_addr, oop value) {
assert(Universe::heap()->is_in(discovered_field_addr), PTR_FORMAT " not in heap", p2i(discovered_field_addr));
HeapAccess<AS_NO_KEEPALIVE>::oop_store(discovered_field_addr,
value);
}
void DiscoveredListIterator::load_ptrs(DEBUG_ONLY(bool allow_null_referent)) {
_current_discovered_addr = java_lang_ref_Reference::discovered_addr_raw(_current_discovered);
oop discovered = java_lang_ref_Reference::discovered(_current_discovered);
assert(_current_discovered_addr && oopDesc::is_oop_or_null(discovered), "Expected an oop or NULL for discovered field at " PTR_FORMAT, p2i(discovered));
_next_discovered = discovered;
_referent = java_lang_ref_Reference::unknown_referent_no_keepalive(_current_discovered);
assert(Universe::heap()->is_in_or_null(_referent), "Wrong oop found in java.lang.Reference object");
assert(allow_null_referent ?
oopDesc::is_oop_or_null(_referent)
: oopDesc::is_oop(_referent), "Expected an oop%s for referent field at " PTR_FORMAT,
(allow_null_referent ? " or NULL" : ""),
p2i(_referent));
}
void DiscoveredListIterator::remove() {
assert(oopDesc::is_oop(_current_discovered), "Dropping a bad reference");
RawAccess<>::oop_store(_current_discovered_addr, oop(NULL));
// First _prev_next ref actually points into DiscoveredList (gross).
oop new_next; if (_next_discovered == _current_discovered) { // At the end of the list, we should make _prev point to itself. // If _ref is the first ref, then _prev_next will be in the DiscoveredList, // and _prev will be NULL.
new_next = _prev_discovered;
} else {
new_next = _next_discovered;
} // Remove Reference object from discovered list. We do not need barriers here, // as we only remove. We will do the barrier when we actually advance the cursor.
RawAccess<>::oop_store(_prev_discovered_addr, new_next);
_removed++;
_refs_list.dec_length(1);
}
void DiscoveredListIterator::complete_enqueue() { if (_prev_discovered != nullptr) { // This is the last object. // Swap refs_list into pending list and set obj's // discovered to what we read from the pending list.
oop old = Universe::swap_reference_pending_list(_refs_list.head());
_enqueue->enqueue(java_lang_ref_Reference::discovered_addr_raw(_prev_discovered), old);
}
}
size_t ReferenceProcessor::process_discovered_list_work(DiscoveredList& refs_list,
BoolObjectClosure* is_alive,
OopClosure* keep_alive,
EnqueueDiscoveredFieldClosure* enqueue, bool do_enqueue_and_clear) {
DiscoveredListIterator iter(refs_list, keep_alive, is_alive, enqueue); while (iter.has_next()) {
iter.load_ptrs(DEBUG_ONLY(discovery_is_concurrent() /* allow_null_referent */)); if (iter.referent() == NULL) { // Reference has been cleared since discovery; only possible if // discovery is concurrent (checked by load_ptrs). Remove // reference from list.
log_dropped_ref(iter, "cleared");
iter.remove();
iter.move_to_next();
} elseif (iter.is_referent_alive()) { // The referent is reachable after all. // Remove reference from list.
log_dropped_ref(iter, "reachable");
iter.remove(); // Update the referent pointer as necessary. Note that this // should not entail any recursive marking because the // referent must already have been traversed.
iter.make_referent_alive();
iter.move_to_next();
} else { if (do_enqueue_and_clear) {
iter.clear_referent();
iter.enqueue();
log_enqueued_ref(iter, "cleared");
} // Keep in discovered list
iter.next();
}
} if (do_enqueue_and_clear) {
iter.complete_enqueue();
refs_list.clear();
}
log_develop_trace(gc, ref)(" Dropped " SIZE_FORMAT " active Refs out of " SIZE_FORMAT " Refs in discovered list " PTR_FORMAT,
iter.removed(), iter.processed(), p2i(&refs_list)); return iter.removed();
}
size_t ReferenceProcessor::process_final_keep_alive_work(DiscoveredList& refs_list,
OopClosure* keep_alive,
EnqueueDiscoveredFieldClosure* enqueue) {
DiscoveredListIterator iter(refs_list, keep_alive, NULL, enqueue); while (iter.has_next()) {
iter.load_ptrs(DEBUG_ONLY(false/* allow_null_referent */)); // keep the referent and followers around
iter.make_referent_alive();
// Self-loop next, to mark the FinalReference not active.
assert(java_lang_ref_Reference::next(iter.obj()) == NULL, "enqueued FinalReference");
java_lang_ref_Reference::set_next_raw(iter.obj(), iter.obj());
assert(iter.removed() == 0, "This phase does not remove anything."); return iter.removed();
}
void
ReferenceProcessor::clear_discovered_references(DiscoveredList& refs_list) {
oop obj = NULL;
oop next = refs_list.head(); while (next != obj) {
obj = next;
next = java_lang_ref_Reference::discovered(obj);
java_lang_ref_Reference::set_discovered_raw(obj, NULL);
}
refs_list.clear();
}
void ReferenceProcessor::abandon_partial_discovery() { // loop over the lists for (uint i = 0; i < _max_num_queues * number_of_subclasses_of_ref(); i++) { if ((i % _max_num_queues) == 0) {
log_develop_trace(gc, ref)("Abandoning %s discovered list", list_name(i));
}
clear_discovered_references(_discovered_refs[i]);
}
}
size_t ReferenceProcessor::total_reference_count(ReferenceType type) const {
DiscoveredList* list = NULL;
switch (type) { case REF_SOFT:
list = _discoveredSoftRefs; break; case REF_WEAK:
list = _discoveredWeakRefs; break; case REF_FINAL:
list = _discoveredFinalRefs; break; case REF_PHANTOM:
list = _discoveredPhantomRefs; break; case REF_NONE: default:
ShouldNotReachHere();
} return total_count(list);
}
bool ReferenceProcessor::need_balance_queues(DiscoveredList refs_lists[]) {
assert(processing_is_mt(), "why balance non-mt processing?"); // _num_queues is the processing degree. Only list entries up to // _num_queues will be processed, so any non-empty lists beyond // that must be redistributed to lists in that range. Even if not // needed for that, balancing may be desirable to eliminate poor // distribution of references among the lists. if (ParallelRefProcBalancingEnabled) { returntrue; // Configuration says do it.
} else { // Configuration says don't balance, but if there are non-empty // lists beyond the processing degree, then must ignore the // configuration and balance anyway. for (uint i = _num_queues; i < _max_num_queues; ++i) { if (!refs_lists[i].is_empty()) { returntrue; // Must balance despite configuration.
}
} returnfalse; // Safe to obey configuration and not balance.
}
}
void ReferenceProcessor::maybe_balance_queues(DiscoveredList refs_lists[]) {
assert(processing_is_mt(), "Should not call this otherwise"); if (need_balance_queues(refs_lists)) {
balance_queues(refs_lists);
}
}
// Balances reference queues. // Move entries from all queues[0, 1, ..., _max_num_q-1] to // queues[0, 1, ..., _num_q-1] because only the first _num_q // corresponding to the active workers will be processed. void ReferenceProcessor::balance_queues(DiscoveredList ref_lists[])
{ // calculate total length
size_t total_refs = 0;
log_develop_trace(gc, ref)("Balance ref_lists ");
log_reflist_counts(ref_lists, _max_num_queues);
for (uint i = 0; i < _max_num_queues; ++i) {
total_refs += ref_lists[i].length();
}
size_t avg_refs = total_refs / _num_queues + 1;
uint to_idx = 0; for (uint from_idx = 0; from_idx < _max_num_queues; from_idx++) { bool move_all = false; if (from_idx >= _num_queues) {
move_all = ref_lists[from_idx].length() > 0;
} while ((ref_lists[from_idx].length() > avg_refs) ||
move_all) {
assert(to_idx < _num_queues, "Sanity Check!"); if (ref_lists[to_idx].length() < avg_refs) { // move superfluous refs
size_t refs_to_move; // Move all the Ref's if the from queue will not be processed. if (move_all) {
refs_to_move = MIN2(ref_lists[from_idx].length(),
avg_refs - ref_lists[to_idx].length());
} else {
refs_to_move = MIN2(ref_lists[from_idx].length() - avg_refs,
avg_refs - ref_lists[to_idx].length());
}
assert(refs_to_move > 0, "otherwise the code below will fail");
oop move_head = ref_lists[from_idx].head();
oop move_tail = move_head;
oop new_head = move_head; // find an element to split the list on for (size_t j = 0; j < refs_to_move; ++j) {
move_tail = new_head;
new_head = java_lang_ref_Reference::discovered(new_head);
}
// Add the chain to the to list. if (ref_lists[to_idx].head() == NULL) { // to list is empty. Make a loop at the end.
java_lang_ref_Reference::set_discovered_raw(move_tail, move_tail);
} else {
java_lang_ref_Reference::set_discovered_raw(move_tail, ref_lists[to_idx].head());
}
ref_lists[to_idx].set_head(move_head);
ref_lists[to_idx].inc_length(refs_to_move);
// Remove the chain from the from list. if (move_tail == new_head) { // We found the end of the from list.
ref_lists[from_idx].set_head(NULL);
} else {
ref_lists[from_idx].set_head(new_head);
}
ref_lists[from_idx].dec_length(refs_to_move); if (ref_lists[from_idx].length() == 0) { break;
}
} else {
to_idx = (to_idx + 1) % _num_queues;
}
}
} #ifdef ASSERT
log_reflist_counts(ref_lists, _num_queues);
size_t balanced_total_refs = 0; for (uint i = 0; i < _num_queues; ++i) {
balanced_total_refs += ref_lists[i].length();
}
assert(total_refs == balanced_total_refs, "Balancing was incomplete"); #endif
}
proxy_task.prepare_run_task(task, num_queues(), processing_is_mt() ? RefProcThreadModel::Multi : RefProcThreadModel::Single, marks_oops_alive); if (processing_is_mt()) {
WorkerThreads* workers = Universe::heap()->safepoint_workers();
assert(workers != NULL, "can not dispatch multi threaded without workers");
assert(workers->active_workers() >= num_queues(), "Ergonomically chosen workers(%u) should be less than or equal to active workers(%u)",
num_queues(), workers->active_workers());
workers->run_task(&proxy_task, num_queues());
} else { for (unsigned i = 0; i < _max_num_queues; ++i) {
proxy_task.work(i);
}
}
}
if (processing_is_mt()) {
RefProcBalanceQueuesTimeTracker tt(KeepAliveFinalRefsPhase, &phase_times);
maybe_balance_queues(_discoveredFinalRefs);
}
// Traverse referents of final references and keep them and followers alive.
RefProcKeepAliveFinalPhaseTask phase_task(*this, &phase_times);
run_task(phase_task, proxy_task, true);
inline DiscoveredList* ReferenceProcessor::get_discovered_list(ReferenceType rt) {
uint id = 0; // Determine the queue index to use for this object. if (_discovery_is_mt) { // During a multi-threaded discovery phase, // each thread saves to its "own" list.
id = WorkerThread::worker_id();
} else { // single-threaded discovery, we save in round-robin // fashion to each of the lists. if (processing_is_mt()) {
id = next_id();
}
}
assert(id < _max_num_queues, "Id is out of bounds id %u and max id %u)", id, _max_num_queues);
// Get the discovered queue to which we will add
DiscoveredList* list = NULL; switch (rt) { case REF_SOFT:
list = &_discoveredSoftRefs[id]; break; case REF_WEAK:
list = &_discoveredWeakRefs[id]; break; case REF_FINAL:
list = &_discoveredFinalRefs[id]; break; case REF_PHANTOM:
list = &_discoveredPhantomRefs[id]; break; case REF_NONE: // we should not reach here if we are an InstanceRefKlass default:
ShouldNotReachHere();
}
log_develop_trace(gc, ref)("Thread %d gets list " PTR_FORMAT, id, p2i(list)); return list;
}
inlinevoid ReferenceProcessor::add_to_discovered_list(DiscoveredList& refs_list,
oop obj,
HeapWord* discovered_addr) {
oop current_head = refs_list.head(); // Prepare value to put into the discovered field. The last ref must have its // discovered field pointing to itself.
oop next_discovered = (current_head != NULL) ? current_head : obj;
bool added = set_discovered_link(discovered_addr, next_discovered); if (added) { // We can always add the object without synchronization: every thread has its // own list head.
refs_list.add_as_head(obj);
log_develop_trace(gc, ref)("Discovered reference (%s) (" PTR_FORMAT ": %s)",
discovery_is_mt() ? "mt" : "st", p2i(obj), obj->klass()->internal_name());
} else {
log_develop_trace(gc, ref)("Already discovered reference (mt) (" PTR_FORMAT ": %s)",
p2i(obj), obj->klass()->internal_name());
}
}
if (discovery_is_stw()) { // Do a raw store here: the field will be visited later when processing // the discovered references.
RawAccess<>::oop_store(discovered_addr, next_discovered);
} else {
HeapAccess<AS_NO_KEEPALIVE>::oop_store(discovered_addr, next_discovered);
} // Always successful. returntrue;
}
// We must make sure this object is only enqueued once. Try to CAS into the discovered_addr.
oop retest; if (discovery_is_stw()) { // Try a raw store here, still making sure that we enqueue only once: the field // will be visited later when processing the discovered references.
retest = RawAccess<>::oop_atomic_cmpxchg(discovered_addr, oop(NULL), next_discovered);
} else {
retest = HeapAccess<AS_NO_KEEPALIVE>::oop_atomic_cmpxchg(discovered_addr, oop(NULL), next_discovered);
} return retest == NULL;
}
#ifndef PRODUCT // Concurrent discovery might allow us to observe j.l.References with NULL // referents, being those cleared concurrently by mutators during (or after) discovery. void ReferenceProcessor::verify_referent(oop obj) { bool concurrent = discovery_is_concurrent();
oop referent = java_lang_ref_Reference::unknown_referent_no_keepalive(obj);
assert(concurrent ? oopDesc::is_oop_or_null(referent) : oopDesc::is_oop(referent), "Bad referent " PTR_FORMAT " found in Reference "
PTR_FORMAT " during %sconcurrent discovery ",
p2i(referent), p2i(obj), concurrent ? "" : "non-");
} #endif
// We mention two of several possible choices here: // #0: if the reference object is not in the "originating generation" // (or part of the heap being collected, indicated by our "span") // we don't treat it specially (i.e. we scan it as we would // a normal oop, treating its references as strong references). // This means that references can't be discovered unless their // referent is also in the same span. This is the simplest, // most "local" and most conservative approach, albeit one // that may cause weak references to be enqueued least promptly. // We call this choice the "ReferenceBasedDiscovery" policy. // #1: the reference object may be in any generation (span), but if // the referent is in the generation (span) being currently collected // then we can discover the reference object, provided // the object has not already been discovered by // a different concurrently running discoverer (as may be the // case, for instance, if the reference object is in G1 old gen and // the referent in G1 young gen), and provided the processing // of this reference object by the current collector will // appear atomically to every other discoverer in the system. // (Thus, for instance, a concurrent discoverer may not // discover references in other generations even if the // referent is in its own generation). This policy may, // in certain cases, enqueue references somewhat sooner than // might Policy #0 above, but at marginally increased cost // and complexity in processing these references. // We call this choice the "ReferentBasedDiscovery" policy. bool ReferenceProcessor::discover_reference(oop obj, ReferenceType rt) { // Make sure we are discovering refs (rather than processing discovered refs). if (!_discovering_refs || !RegisterReferences) { returnfalse;
}
if (RefDiscoveryPolicy == ReferenceBasedDiscovery &&
!is_subject_to_discovery(obj)) { // Reference is not in the originating generation; // don't treat it specially (i.e. we want to scan it as a normal // object with strong references). returnfalse;
}
// We only discover references whose referents are not (yet) // known to be strongly reachable. if (is_alive_non_header() != NULL) {
verify_referent(obj);
oop referent = java_lang_ref_Reference::unknown_referent_no_keepalive(obj); if (is_alive_non_header()->do_object_b(referent)) { returnfalse; // referent is reachable
}
} if (rt == REF_SOFT) { // For soft refs we can decide now if these are not // current candidates for clearing, in which case we // can mark through them now, rather than delaying that // to the reference-processing phase. Since all current // time-stamp policies advance the soft-ref clock only // at a full collection cycle, this is always currently // accurate. if (!_current_soft_ref_policy->should_clear_reference(obj, _soft_ref_timestamp_clock)) { returnfalse;
}
}
ResourceMark rm; // Needed for tracing.
HeapWord* const discovered_addr = java_lang_ref_Reference::discovered_addr_raw(obj); const oop discovered = java_lang_ref_Reference::discovered(obj);
assert(oopDesc::is_oop_or_null(discovered), "Expected an oop or NULL for discovered field at " PTR_FORMAT, p2i(discovered)); if (discovered != NULL) { // The reference has already been discovered...
log_develop_trace(gc, ref)("Already discovered reference (" PTR_FORMAT ": %s)",
p2i(obj), obj->klass()->internal_name()); if (RefDiscoveryPolicy == ReferentBasedDiscovery) { // assumes that an object is not processed twice; // if it's been already discovered it must be on another // generation's discovered list; so we won't discover it. returnfalse;
} else {
assert(RefDiscoveryPolicy == ReferenceBasedDiscovery, "Unrecognized policy"); // Check assumption that an object is not potentially // discovered twice except by concurrent collectors that potentially // trace the same Reference object twice.
assert(UseG1GC, "Only possible with a concurrent marking collector"); returntrue;
}
}
if (RefDiscoveryPolicy == ReferentBasedDiscovery) {
verify_referent(obj); // Discover if and only if EITHER: // .. reference is in our span, OR // .. we are a stw discoverer and referent is in our span if (is_subject_to_discovery(obj) ||
(discovery_is_stw() &&
is_subject_to_discovery(java_lang_ref_Reference::unknown_referent_no_keepalive(obj)))) {
} else { returnfalse;
}
} else {
assert(RefDiscoveryPolicy == ReferenceBasedDiscovery &&
is_subject_to_discovery(obj), "code inconsistency");
}
// Get the right type of discovered queue head.
DiscoveredList* list = get_discovered_list(rt);
add_to_discovered_list(*list, obj, discovered_addr);
assert(oopDesc::is_oop(obj), "Discovered a bad reference");
verify_referent(obj); returntrue;
}
void ReferenceProcessor::preclean_discovered_references(BoolObjectClosure* is_alive,
EnqueueDiscoveredFieldClosure* enqueue,
YieldClosure* yield,
GCTimer* gc_timer) { // These lists can be handled here in any order and, indeed, concurrently.
// Soft references
{
GCTraceTime(Debug, gc, ref) tm("Preclean SoftReferences", gc_timer);
log_reflist("SoftRef before: ", _discoveredSoftRefs, _max_num_queues); for (uint i = 0; i < _max_num_queues; i++) { if (yield->should_return()) { return;
} if (preclean_discovered_reflist(_discoveredSoftRefs[i], is_alive,
enqueue, yield)) {
log_reflist("SoftRef abort: ", _discoveredSoftRefs, _max_num_queues); return;
}
}
log_reflist("SoftRef after: ", _discoveredSoftRefs, _max_num_queues);
}
// Weak references
{
GCTraceTime(Debug, gc, ref) tm("Preclean WeakReferences", gc_timer);
log_reflist("WeakRef before: ", _discoveredWeakRefs, _max_num_queues); for (uint i = 0; i < _max_num_queues; i++) { if (yield->should_return()) { return;
} if (preclean_discovered_reflist(_discoveredWeakRefs[i], is_alive,
enqueue, yield)) {
log_reflist("WeakRef abort: ", _discoveredWeakRefs, _max_num_queues); return;
}
}
log_reflist("WeakRef after: ", _discoveredWeakRefs, _max_num_queues);
}
// Final references
{
GCTraceTime(Debug, gc, ref) tm("Preclean FinalReferences", gc_timer);
log_reflist("FinalRef before: ", _discoveredFinalRefs, _max_num_queues); for (uint i = 0; i < _max_num_queues; i++) { if (yield->should_return()) { return;
} if (preclean_discovered_reflist(_discoveredFinalRefs[i], is_alive,
enqueue, yield)) {
log_reflist("FinalRef abort: ", _discoveredFinalRefs, _max_num_queues); return;
}
}
log_reflist("FinalRef after: ", _discoveredFinalRefs, _max_num_queues);
}
int j = i / _max_num_queues; switch (j) { case 0: return"SoftRef"; case 1: return"WeakRef"; case 2: return"FinalRef"; case 3: return"PhantomRef";
}
ShouldNotReachHere(); return NULL;
}
uint RefProcMTDegreeAdjuster::ergo_proc_thread_count(size_t ref_count,
uint max_threads,
RefProcPhases phase) const {
assert(0 < max_threads, "must allow at least one thread");
if (use_max_threads(phase) || (ReferencesPerThread == 0)) { return max_threads;
}
bool RefProcMTDegreeAdjuster::use_max_threads(RefProcPhases phase) const { // Even a small number of references in this phase could produce large amounts of work. return phase == ReferenceProcessor::KeepAliveFinalRefsPhase;
}
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