| /* |
| * Copyright (c) 2018, 2019, Red Hat, Inc. All rights reserved. |
| * |
| * 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 "precompiled.hpp" |
| |
| #include "gc/shenandoah/shenandoahFreeSet.hpp" |
| #include "gc/shenandoah/shenandoahHeap.inline.hpp" |
| #include "gc/shenandoah/shenandoahPacer.hpp" |
| #include "gc/shenandoah/shenandoahPhaseTimings.hpp" |
| #include "runtime/mutexLocker.hpp" |
| |
| /* |
| * In normal concurrent cycle, we have to pace the application to let GC finish. |
| * |
| * Here, we do not know how large would be the collection set, and what are the |
| * relative performances of the each stage in the concurrent cycle, and so we have to |
| * make some assumptions. |
| * |
| * For concurrent mark, there is no clear notion of progress. The moderately accurate |
| * and easy to get metric is the amount of live objects the mark had encountered. But, |
| * that does directly correlate with the used heap, because the heap might be fully |
| * dead or fully alive. We cannot assume either of the extremes: we would either allow |
| * application to run out of memory if we assume heap is fully dead but it is not, and, |
| * conversely, we would pacify application excessively if we assume heap is fully alive |
| * but it is not. So we need to guesstimate the particular expected value for heap liveness. |
| * The best way to do this is apparently recording the past history. |
| * |
| * For concurrent evac and update-refs, we are walking the heap per-region, and so the |
| * notion of progress is clear: we get reported the "used" size from the processed regions |
| * and use the global heap-used as the baseline. |
| * |
| * The allocatable space when GC is running is "free" at the start of phase, but the |
| * accounted budget is based on "used". So, we need to adjust the tax knowing that. |
| */ |
| |
| void ShenandoahPacer::setup_for_mark() { |
| assert(ShenandoahPacing, "Only be here when pacing is enabled"); |
| |
| size_t live = update_and_get_progress_history(); |
| size_t free = _heap->free_set()->available(); |
| |
| size_t non_taxable = free * ShenandoahPacingCycleSlack / 100; |
| size_t taxable = free - non_taxable; |
| |
| double tax = 1.0 * live / taxable; // base tax for available free space |
| tax *= 1; // mark can succeed with immediate garbage, claim all available space |
| tax *= ShenandoahPacingSurcharge; // additional surcharge to help unclutter heap |
| |
| restart_with(non_taxable, tax); |
| |
| log_info(gc, ergo)("Pacer for Mark. Expected Live: " SIZE_FORMAT "%s, Free: " SIZE_FORMAT "%s, " |
| "Non-Taxable: " SIZE_FORMAT "%s, Alloc Tax Rate: %.1fx", |
| byte_size_in_proper_unit(live), proper_unit_for_byte_size(live), |
| byte_size_in_proper_unit(free), proper_unit_for_byte_size(free), |
| byte_size_in_proper_unit(non_taxable), proper_unit_for_byte_size(non_taxable), |
| tax); |
| } |
| |
| void ShenandoahPacer::setup_for_evac() { |
| assert(ShenandoahPacing, "Only be here when pacing is enabled"); |
| |
| size_t used = _heap->collection_set()->used(); |
| size_t free = _heap->free_set()->available(); |
| |
| size_t non_taxable = free * ShenandoahPacingCycleSlack / 100; |
| size_t taxable = free - non_taxable; |
| |
| double tax = 1.0 * used / taxable; // base tax for available free space |
| tax *= 2; // evac is followed by update-refs, claim 1/2 of remaining free |
| tax = MAX2<double>(1, tax); // never allocate more than GC processes during the phase |
| tax *= ShenandoahPacingSurcharge; // additional surcharge to help unclutter heap |
| |
| restart_with(non_taxable, tax); |
| |
| log_info(gc, ergo)("Pacer for Evacuation. Used CSet: " SIZE_FORMAT "%s, Free: " SIZE_FORMAT "%s, " |
| "Non-Taxable: " SIZE_FORMAT "%s, Alloc Tax Rate: %.1fx", |
| byte_size_in_proper_unit(used), proper_unit_for_byte_size(used), |
| byte_size_in_proper_unit(free), proper_unit_for_byte_size(free), |
| byte_size_in_proper_unit(non_taxable), proper_unit_for_byte_size(non_taxable), |
| tax); |
| } |
| |
| void ShenandoahPacer::setup_for_updaterefs() { |
| assert(ShenandoahPacing, "Only be here when pacing is enabled"); |
| |
| size_t used = _heap->used(); |
| size_t free = _heap->free_set()->available(); |
| |
| size_t non_taxable = free * ShenandoahPacingCycleSlack / 100; |
| size_t taxable = free - non_taxable; |
| |
| double tax = 1.0 * used / taxable; // base tax for available free space |
| tax *= 1; // update-refs is the last phase, claim the remaining free |
| tax = MAX2<double>(1, tax); // never allocate more than GC processes during the phase |
| tax *= ShenandoahPacingSurcharge; // additional surcharge to help unclutter heap |
| |
| restart_with(non_taxable, tax); |
| |
| log_info(gc, ergo)("Pacer for Update Refs. Used: " SIZE_FORMAT "%s, Free: " SIZE_FORMAT "%s, " |
| "Non-Taxable: " SIZE_FORMAT "%s, Alloc Tax Rate: %.1fx", |
| byte_size_in_proper_unit(used), proper_unit_for_byte_size(used), |
| byte_size_in_proper_unit(free), proper_unit_for_byte_size(free), |
| byte_size_in_proper_unit(non_taxable), proper_unit_for_byte_size(non_taxable), |
| tax); |
| } |
| |
| /* |
| * In idle phase, we have to pace the application to let control thread react with GC start. |
| * |
| * Here, we have rendezvous with concurrent thread that adds up the budget as it acknowledges |
| * it had seen recent allocations. It will naturally pace the allocations if control thread is |
| * not catching up. To bootstrap this feedback cycle, we need to start with some initial budget |
| * for applications to allocate at. |
| */ |
| |
| void ShenandoahPacer::setup_for_idle() { |
| assert(ShenandoahPacing, "Only be here when pacing is enabled"); |
| |
| size_t initial = _heap->max_capacity() / 100 * ShenandoahPacingIdleSlack; |
| double tax = 1; |
| |
| restart_with(initial, tax); |
| |
| log_info(gc, ergo)("Pacer for Idle. Initial: " SIZE_FORMAT "%s, Alloc Tax Rate: %.1fx", |
| byte_size_in_proper_unit(initial), proper_unit_for_byte_size(initial), |
| tax); |
| } |
| |
| /* |
| * There is no useful notion of progress for these operations. To avoid stalling |
| * the allocators unnecessarily, allow them to run unimpeded. |
| */ |
| |
| void ShenandoahPacer::setup_for_preclean() { |
| assert(ShenandoahPacing, "Only be here when pacing is enabled"); |
| |
| size_t initial = _heap->max_capacity(); |
| restart_with(initial, 1.0); |
| |
| log_info(gc, ergo)("Pacer for Precleaning. Non-Taxable: " SIZE_FORMAT "%s", |
| byte_size_in_proper_unit(initial), proper_unit_for_byte_size(initial)); |
| } |
| |
| void ShenandoahPacer::setup_for_reset() { |
| assert(ShenandoahPacing, "Only be here when pacing is enabled"); |
| |
| size_t initial = _heap->max_capacity(); |
| restart_with(initial, 1.0); |
| |
| log_info(gc, ergo)("Pacer for Reset. Non-Taxable: " SIZE_FORMAT "%s", |
| byte_size_in_proper_unit(initial), proper_unit_for_byte_size(initial)); |
| } |
| |
| size_t ShenandoahPacer::update_and_get_progress_history() { |
| if (_progress == -1) { |
| // First initialization, report some prior |
| Atomic::store((intptr_t)PACING_PROGRESS_ZERO, &_progress); |
| return (size_t) (_heap->max_capacity() * 0.1); |
| } else { |
| // Record history, and reply historical data |
| _progress_history->add(_progress); |
| Atomic::store((intptr_t)PACING_PROGRESS_ZERO, &_progress); |
| return (size_t) (_progress_history->avg() * HeapWordSize); |
| } |
| } |
| |
| void ShenandoahPacer::restart_with(size_t non_taxable_bytes, double tax_rate) { |
| size_t initial = (size_t)(non_taxable_bytes * tax_rate) >> LogHeapWordSize; |
| STATIC_ASSERT(sizeof(size_t) <= sizeof(intptr_t)); |
| Atomic::xchg((intptr_t)initial, &_budget, memory_order_relaxed); |
| Atomic::store(tax_rate, &_tax_rate); |
| Atomic::inc(&_epoch); |
| |
| // Shake up stalled waiters after budget update. |
| _need_notify_waiters.try_set(); |
| } |
| |
| bool ShenandoahPacer::claim_for_alloc(size_t words, bool force) { |
| assert(ShenandoahPacing, "Only be here when pacing is enabled"); |
| |
| intptr_t tax = MAX2<intptr_t>(1, words * Atomic::load(&_tax_rate)); |
| |
| intptr_t cur = 0; |
| intptr_t new_val = 0; |
| do { |
| cur = Atomic::load(&_budget); |
| if (cur < tax && !force) { |
| // Progress depleted, alas. |
| return false; |
| } |
| new_val = cur - tax; |
| } while (Atomic::cmpxchg(new_val, &_budget, cur, memory_order_relaxed) != cur); |
| return true; |
| } |
| |
| void ShenandoahPacer::unpace_for_alloc(intptr_t epoch, size_t words) { |
| assert(ShenandoahPacing, "Only be here when pacing is enabled"); |
| |
| if (Atomic::load(&_epoch) != epoch) { |
| // Stale ticket, no need to unpace. |
| return; |
| } |
| |
| size_t tax = MAX2<size_t>(1, words * Atomic::load(&_tax_rate)); |
| add_budget(tax); |
| } |
| |
| intptr_t ShenandoahPacer::epoch() { |
| return Atomic::load(&_epoch); |
| } |
| |
| void ShenandoahPacer::pace_for_alloc(size_t words) { |
| assert(ShenandoahPacing, "Only be here when pacing is enabled"); |
| |
| // Fast path: try to allocate right away |
| bool claimed = claim_for_alloc(words, false); |
| if (claimed) { |
| return; |
| } |
| |
| // Forcefully claim the budget: it may go negative at this point, and |
| // GC should replenish for this and subsequent allocations. After this claim, |
| // we would wait a bit until our claim is matched by additional progress, |
| // or the time budget depletes. |
| claimed = claim_for_alloc(words, true); |
| assert(claimed, "Should always succeed"); |
| |
| // Threads that are attaching should not block at all: they are not |
| // fully initialized yet. Blocking them would be awkward. |
| // This is probably the path that allocates the thread oop itself. |
| if (JavaThread::current()->is_attaching_via_jni()) { |
| return; |
| } |
| |
| double start = os::elapsedTime(); |
| |
| size_t max_ms = ShenandoahPacingMaxDelay; |
| size_t total_ms = 0; |
| |
| while (true) { |
| // We could instead assist GC, but this would suffice for now. |
| size_t cur_ms = (max_ms > total_ms) ? (max_ms - total_ms) : 1; |
| wait(cur_ms); |
| |
| double end = os::elapsedTime(); |
| total_ms = (size_t)((end - start) * 1000); |
| |
| if (total_ms > max_ms || Atomic::load(&_budget) >= 0) { |
| // Exiting if either: |
| // a) Spent local time budget to wait for enough GC progress. |
| // Breaking out and allocating anyway, which may mean we outpace GC, |
| // and start Degenerated GC cycle. |
| // b) The budget had been replenished, which means our claim is satisfied. |
| ShenandoahThreadLocalData::add_paced_time(JavaThread::current(), end - start); |
| break; |
| } |
| } |
| } |
| |
| void ShenandoahPacer::wait(size_t time_ms) { |
| // Perform timed wait. It works like like sleep(), except without modifying |
| // the thread interruptible status. MonitorLocker also checks for safepoints. |
| assert(time_ms > 0, "Should not call this with zero argument, as it would stall until notify"); |
| assert(time_ms <= LONG_MAX, "Sanity"); |
| MonitorLockerEx locker(_wait_monitor); |
| _wait_monitor->wait(!Mutex::_no_safepoint_check_flag, (long)time_ms); |
| } |
| |
| void ShenandoahPacer::notify_waiters() { |
| if (_need_notify_waiters.try_unset()) { |
| MonitorLockerEx locker(_wait_monitor); |
| _wait_monitor->notify_all(); |
| } |
| } |
| |
| void ShenandoahPacer::flush_stats_to_cycle() { |
| double sum = 0; |
| for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { |
| sum += ShenandoahThreadLocalData::paced_time(t); |
| } |
| ShenandoahHeap::heap()->phase_timings()->record_phase_time(ShenandoahPhaseTimings::pacing, sum); |
| } |
| |
| void ShenandoahPacer::print_cycle_on(outputStream* out) { |
| MutexLocker lock(Threads_lock); |
| |
| double now = os::elapsedTime(); |
| double total = now - _last_time; |
| _last_time = now; |
| |
| out->cr(); |
| out->print_cr("Allocation pacing accrued:"); |
| |
| size_t threads_total = 0; |
| size_t threads_nz = 0; |
| double sum = 0; |
| for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { |
| double d = ShenandoahThreadLocalData::paced_time(t); |
| if (d > 0) { |
| threads_nz++; |
| sum += d; |
| out->print_cr(" %5.0f of %5.0f ms (%5.1f%%): %s", |
| d * 1000, total * 1000, d/total*100, t->name()); |
| } |
| threads_total++; |
| ShenandoahThreadLocalData::reset_paced_time(t); |
| } |
| out->print_cr(" %5.0f of %5.0f ms (%5.1f%%): <total>", |
| sum * 1000, total * 1000, sum/total*100); |
| |
| if (threads_total > 0) { |
| out->print_cr(" %5.0f of %5.0f ms (%5.1f%%): <average total>", |
| sum / threads_total * 1000, total * 1000, sum / threads_total / total * 100); |
| } |
| if (threads_nz > 0) { |
| out->print_cr(" %5.0f of %5.0f ms (%5.1f%%): <average non-zero>", |
| sum / threads_nz * 1000, total * 1000, sum / threads_nz / total * 100); |
| } |
| out->cr(); |
| } |