--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/z/zDirector.cpp Tue Jun 12 17:40:28 2018 +0200
@@ -0,0 +1,222 @@
+/*
+ * Copyright (c) 2015, 2018, 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.
+ */
+
+#include "precompiled.hpp"
+#include "gc/z/zCollectedHeap.hpp"
+#include "gc/z/zDirector.hpp"
+#include "gc/z/zHeap.inline.hpp"
+#include "gc/z/zStat.hpp"
+#include "gc/z/zUtils.hpp"
+#include "logging/log.hpp"
+
+const double ZDirector::one_in_1000 = 3.290527;
+
+ZDirector::ZDirector() :
+ _metronome(ZStatAllocRate::sample_hz) {
+ set_name("ZDirector");
+ create_and_start();
+}
+
+void ZDirector::sample_allocation_rate() const {
+ // Sample allocation rate. This is needed by rule_allocation_rate()
+ // below to estimate the time we have until we run out of memory.
+ const double bytes_per_second = ZStatAllocRate::sample_and_reset();
+
+ log_debug(gc, alloc)("Allocation Rate: %.3fMB/s, Avg: %.3f(+/-%.3f)MB/s",
+ bytes_per_second / M,
+ ZStatAllocRate::avg() / M,
+ ZStatAllocRate::avg_sd() / M);
+}
+
+bool ZDirector::is_first() const {
+ return ZStatCycle::ncycles() == 0;
+}
+
+bool ZDirector::is_warm() const {
+ return ZStatCycle::ncycles() >= 3;
+}
+
+bool ZDirector::rule_timer() const {
+ if (ZCollectionInterval == 0) {
+ // Rule disabled
+ return false;
+ }
+
+ // Perform GC if timer has expired.
+ const double time_since_last_gc = ZStatCycle::time_since_last();
+ const double time_until_gc = ZCollectionInterval - time_since_last_gc;
+
+ log_debug(gc, director)("Rule: Timer, Interval: %us, TimeUntilGC: %.3lfs",
+ ZCollectionInterval, time_until_gc);
+
+ return time_until_gc <= 0;
+}
+
+bool ZDirector::rule_warmup() const {
+ if (is_warm()) {
+ // Rule disabled
+ return false;
+ }
+
+ // Perform GC if heap usage passes 10/20/30% and no other GC has been
+ // performed yet. This allows us to get some early samples of the GC
+ // duration, which is needed by the other rules.
+ const size_t max_capacity = ZHeap::heap()->max_capacity();
+ const size_t used = ZHeap::heap()->used();
+ const double used_threshold_percent = (ZStatCycle::ncycles() + 1) * 0.1;
+ const size_t used_threshold = max_capacity * used_threshold_percent;
+
+ log_debug(gc, director)("Rule: Warmup %.0f%%, Used: " SIZE_FORMAT "MB, UsedThreshold: " SIZE_FORMAT "MB",
+ used_threshold_percent * 100, used / M, used_threshold / M);
+
+ return used >= used_threshold;
+}
+
+bool ZDirector::rule_allocation_rate() const {
+ if (is_first()) {
+ // Rule disabled
+ return false;
+ }
+
+ // Perform GC if the estimated max allocation rate indicates that we
+ // will run out of memory. The estimated max allocation rate is based
+ // on the moving average of the sampled allocation rate plus a safety
+ // margin based on variations in the allocation rate and unforseen
+ // allocation spikes.
+
+ // Calculate amount of free memory available to Java threads. Note that
+ // the heap reserve is not available to Java threads and is therefore not
+ // considered part of the free memory.
+ const size_t max_capacity = ZHeap::heap()->max_capacity();
+ const size_t max_reserve = ZHeap::heap()->max_reserve();
+ const size_t used = ZHeap::heap()->used();
+ const size_t free_with_reserve = max_capacity - used;
+ const size_t free = free_with_reserve - MIN2(free_with_reserve, max_reserve);
+
+ // Calculate time until OOM given the max allocation rate and the amount
+ // of free memory. The allocation rate is a moving average and we multiply
+ // that with an alllcation spike tolerance factor to guard against unforseen
+ // phase changes in the allocate rate. We then add ~3.3 sigma to account for
+ // the allocation rate variance, which means the probablility is 1 in 1000
+ // that a sample is outside of the confidence interval.
+ const double max_alloc_rate = (ZStatAllocRate::avg() * ZAllocationSpikeTolerance) + (ZStatAllocRate::avg_sd() * one_in_1000);
+ const double time_until_oom = free / (max_alloc_rate + 1.0); // Plus 1.0B/s to avoid division by zero
+
+ // Calculate max duration of a GC cycle. The duration of GC is a moving
+ // average, we add ~3.3 sigma to account for the GC duration variance.
+ const AbsSeq& duration_of_gc = ZStatCycle::normalized_duration();
+ const double max_duration_of_gc = duration_of_gc.davg() + (duration_of_gc.dsd() * one_in_1000);
+
+ // Calculate time until GC given the time until OOM and max duration of GC.
+ // We also deduct the sample interval, so that we don't overshoot the target
+ // time and end up starting the GC too late in the next interval.
+ const double sample_interval = 1.0 / ZStatAllocRate::sample_hz;
+ const double time_until_gc = time_until_oom - max_duration_of_gc - sample_interval;
+
+ log_debug(gc, director)("Rule: Allocation Rate, MaxAllocRate: %.3lfMB/s, Free: " SIZE_FORMAT "MB, MaxDurationOfGC: %.3lfs, TimeUntilGC: %.3lfs",
+ max_alloc_rate / M, free / M, max_duration_of_gc, time_until_gc);
+
+ return time_until_gc <= 0;
+}
+
+bool ZDirector::rule_proactive() const {
+ if (!ZProactive || !is_warm()) {
+ // Rule disabled
+ return false;
+ }
+
+ // Perform GC if the impact of doing so, in terms of application throughput
+ // reduction, is considered acceptable. This rule allows us to keep the heap
+ // size down and allow reference processing to happen even when we have a lot
+ // of free space on the heap.
+
+ // Only consider doing a proactive GC if the heap usage has grown by at least
+ // 10% of the max capacity since the previous GC, or more than 5 minutes has
+ // passed since the previous GC. This helps avoid superfluous GCs when running
+ // applications with very low allocation rate.
+ const size_t used_after_last_gc = ZStatHeap::used_at_relocate_end();
+ const size_t used_increase_threshold = ZHeap::heap()->max_capacity() * 0.10; // 10%
+ const size_t used_threshold = used_after_last_gc + used_increase_threshold;
+ const size_t used = ZHeap::heap()->used();
+ const double time_since_last_gc = ZStatCycle::time_since_last();
+ const double time_since_last_gc_threshold = 5 * 60; // 5 minutes
+ if (used < used_threshold && time_since_last_gc < time_since_last_gc_threshold) {
+ // Don't even consider doing a proactive GC
+ log_debug(gc, director)("Rule: Proactive, UsedUntilEnabled: " SIZE_FORMAT "MB, TimeUntilEnabled: %.3lfs",
+ (used_threshold - used) / M,
+ time_since_last_gc_threshold - time_since_last_gc);
+ return false;
+ }
+
+ const double assumed_throughput_drop_during_gc = 0.50; // 50%
+ const double acceptable_throughput_drop = 0.01; // 1%
+ const AbsSeq& duration_of_gc = ZStatCycle::normalized_duration();
+ const double max_duration_of_gc = duration_of_gc.davg() + (duration_of_gc.dsd() * one_in_1000);
+ const double acceptable_gc_interval = max_duration_of_gc * ((assumed_throughput_drop_during_gc / acceptable_throughput_drop) - 1.0);
+ const double time_until_gc = acceptable_gc_interval - time_since_last_gc;
+
+ log_debug(gc, director)("Rule: Proactive, AcceptableGCInterval: %.3lfs, TimeSinceLastGC: %.3lfs, TimeUntilGC: %.3lfs",
+ acceptable_gc_interval, time_since_last_gc, time_until_gc);
+
+ return time_until_gc <= 0;
+}
+
+GCCause::Cause ZDirector::make_gc_decision() const {
+ // Rule 0: Timer
+ if (rule_timer()) {
+ return GCCause::_z_timer;
+ }
+
+ // Rule 1: Warmup
+ if (rule_warmup()) {
+ return GCCause::_z_warmup;
+ }
+
+ // Rule 2: Allocation rate
+ if (rule_allocation_rate()) {
+ return GCCause::_z_allocation_rate;
+ }
+
+ // Rule 3: Proactive
+ if (rule_proactive()) {
+ return GCCause::_z_proactive;
+ }
+
+ // No GC
+ return GCCause::_no_gc;
+}
+
+void ZDirector::run_service() {
+ // Main loop
+ while (_metronome.wait_for_tick()) {
+ sample_allocation_rate();
+ const GCCause::Cause cause = make_gc_decision();
+ if (cause != GCCause::_no_gc) {
+ ZCollectedHeap::heap()->collect(cause);
+ }
+ }
+}
+
+void ZDirector::stop_service() {
+ _metronome.stop();
+}