--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.cpp Mon Dec 10 15:47:44 2018 +0100
@@ -0,0 +1,214 @@
+/*
+ * Copyright (c) 2018, 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/heuristics/shenandoahAdaptiveHeuristics.hpp"
+#include "gc/shenandoah/shenandoahCollectionSet.hpp"
+#include "gc/shenandoah/shenandoahFreeSet.hpp"
+#include "gc/shenandoah/shenandoahHeapRegion.hpp"
+#include "logging/log.hpp"
+#include "logging/logTag.hpp"
+#include "utilities/quickSort.hpp"
+
+ShenandoahAdaptiveHeuristics::ShenandoahAdaptiveHeuristics() :
+ ShenandoahHeuristics(),
+ _cycle_gap_history(new TruncatedSeq(5)),
+ _conc_mark_duration_history(new TruncatedSeq(5)),
+ _conc_uprefs_duration_history(new TruncatedSeq(5)) {
+
+ SHENANDOAH_ERGO_ENABLE_FLAG(ExplicitGCInvokesConcurrent);
+ SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahImplicitGCInvokesConcurrent);
+
+ // Final configuration checks
+ SHENANDOAH_CHECK_FLAG_SET(ShenandoahSATBBarrier);
+ SHENANDOAH_CHECK_FLAG_SET(ShenandoahReadBarrier);
+ SHENANDOAH_CHECK_FLAG_SET(ShenandoahWriteBarrier);
+ SHENANDOAH_CHECK_FLAG_SET(ShenandoahStoreValReadBarrier);
+ SHENANDOAH_CHECK_FLAG_SET(ShenandoahKeepAliveBarrier);
+ SHENANDOAH_CHECK_FLAG_SET(ShenandoahCASBarrier);
+ SHENANDOAH_CHECK_FLAG_SET(ShenandoahAcmpBarrier);
+ SHENANDOAH_CHECK_FLAG_SET(ShenandoahCloneBarrier);
+}
+
+ShenandoahAdaptiveHeuristics::~ShenandoahAdaptiveHeuristics() {}
+
+void ShenandoahAdaptiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
+ RegionData* data, size_t size,
+ size_t actual_free) {
+ size_t garbage_threshold = ShenandoahHeapRegion::region_size_bytes() * ShenandoahGarbageThreshold / 100;
+
+ // The logic for cset selection in adaptive is as follows:
+ //
+ // 1. We cannot get cset larger than available free space. Otherwise we guarantee OOME
+ // during evacuation, and thus guarantee full GC. In practice, we also want to let
+ // application to allocate something. This is why we limit CSet to some fraction of
+ // available space. In non-overloaded heap, max_cset would contain all plausible candidates
+ // over garbage threshold.
+ //
+ // 2. We should not get cset too low so that free threshold would not be met right
+ // after the cycle. Otherwise we get back-to-back cycles for no reason if heap is
+ // too fragmented. In non-overloaded non-fragmented heap min_garbage would be around zero.
+ //
+ // Therefore, we start by sorting the regions by garbage. Then we unconditionally add the best candidates
+ // before we meet min_garbage. Then we add all candidates that fit with a garbage threshold before
+ // we hit max_cset. When max_cset is hit, we terminate the cset selection. Note that in this scheme,
+ // ShenandoahGarbageThreshold is the soft threshold which would be ignored until min_garbage is hit.
+
+ size_t capacity = ShenandoahHeap::heap()->capacity();
+ size_t free_target = ShenandoahMinFreeThreshold * capacity / 100;
+ size_t min_garbage = free_target > actual_free ? (free_target - actual_free) : 0;
+ size_t max_cset = (size_t)(1.0 * ShenandoahEvacReserve * capacity / 100 / ShenandoahEvacWaste);
+
+ log_info(gc, ergo)("Adaptive CSet Selection. Target Free: " SIZE_FORMAT "M, Actual Free: "
+ SIZE_FORMAT "M, Max CSet: " SIZE_FORMAT "M, Min Garbage: " SIZE_FORMAT "M",
+ free_target / M, actual_free / M, max_cset / M, min_garbage / M);
+
+ // Better select garbage-first regions
+ QuickSort::sort<RegionData>(data, (int)size, compare_by_garbage, false);
+
+ size_t cur_cset = 0;
+ size_t cur_garbage = 0;
+ _bytes_in_cset = 0;
+
+ for (size_t idx = 0; idx < size; idx++) {
+ ShenandoahHeapRegion* r = data[idx]._region;
+
+ size_t new_cset = cur_cset + r->get_live_data_bytes();
+ size_t new_garbage = cur_garbage + r->garbage();
+
+ if (new_cset > max_cset) {
+ break;
+ }
+
+ if ((new_garbage < min_garbage) || (r->garbage() > garbage_threshold)) {
+ cset->add_region(r);
+ _bytes_in_cset += r->used();
+ cur_cset = new_cset;
+ cur_garbage = new_garbage;
+ }
+ }
+}
+
+void ShenandoahAdaptiveHeuristics::record_cycle_start() {
+ ShenandoahHeuristics::record_cycle_start();
+ double last_cycle_gap = (_cycle_start - _last_cycle_end);
+ _cycle_gap_history->add(last_cycle_gap);
+}
+
+void ShenandoahAdaptiveHeuristics::record_phase_time(ShenandoahPhaseTimings::Phase phase, double secs) {
+ if (phase == ShenandoahPhaseTimings::conc_mark) {
+ _conc_mark_duration_history->add(secs);
+ } else if (phase == ShenandoahPhaseTimings::conc_update_refs) {
+ _conc_uprefs_duration_history->add(secs);
+ } // Else ignore
+}
+
+bool ShenandoahAdaptiveHeuristics::should_start_normal_gc() const {
+ ShenandoahHeap* heap = ShenandoahHeap::heap();
+ size_t capacity = heap->capacity();
+ size_t available = heap->free_set()->available();
+
+ // Check if we are falling below the worst limit, time to trigger the GC, regardless of
+ // anything else.
+ size_t min_threshold = ShenandoahMinFreeThreshold * heap->capacity() / 100;
+ if (available < min_threshold) {
+ log_info(gc)("Trigger: Free (" SIZE_FORMAT "M) is below minimum threshold (" SIZE_FORMAT "M)",
+ available / M, min_threshold / M);
+ return true;
+ }
+
+ // Check if are need to learn a bit about the application
+ const size_t max_learn = ShenandoahLearningSteps;
+ if (_gc_times_learned < max_learn) {
+ size_t init_threshold = ShenandoahInitFreeThreshold * heap->capacity() / 100;
+ if (available < init_threshold) {
+ log_info(gc)("Trigger: Learning " SIZE_FORMAT " of " SIZE_FORMAT ". Free (" SIZE_FORMAT "M) is below initial threshold (" SIZE_FORMAT "M)",
+ _gc_times_learned + 1, max_learn, available / M, init_threshold / M);
+ return true;
+ }
+ }
+
+ // Check if allocation headroom is still okay. This also factors in:
+ // 1. Some space to absorb allocation spikes
+ // 2. Accumulated penalties from Degenerated and Full GC
+
+ size_t allocation_headroom = available;
+
+ size_t spike_headroom = ShenandoahAllocSpikeFactor * capacity / 100;
+ size_t penalties = _gc_time_penalties * capacity / 100;
+
+ allocation_headroom -= MIN2(allocation_headroom, spike_headroom);
+ allocation_headroom -= MIN2(allocation_headroom, penalties);
+
+ // TODO: Allocation rate is way too averaged to be useful during state changes
+
+ double average_gc = _gc_time_history->avg();
+ double time_since_last = time_since_last_gc();
+ double allocation_rate = heap->bytes_allocated_since_gc_start() / time_since_last;
+
+ if (average_gc > allocation_headroom / allocation_rate) {
+ log_info(gc)("Trigger: Average GC time (%.2f ms) is above the time for allocation rate (%.2f MB/s) to deplete free headroom (" SIZE_FORMAT "M)",
+ average_gc * 1000, allocation_rate / M, allocation_headroom / M);
+ log_info(gc, ergo)("Free headroom: " SIZE_FORMAT "M (free) - " SIZE_FORMAT "M (spike) - " SIZE_FORMAT "M (penalties) = " SIZE_FORMAT "M",
+ available / M, spike_headroom / M, penalties / M, allocation_headroom / M);
+ return true;
+ }
+
+ return ShenandoahHeuristics::should_start_normal_gc();
+}
+
+bool ShenandoahAdaptiveHeuristics::should_start_update_refs() {
+ if (! _update_refs_adaptive) {
+ return _update_refs_early;
+ }
+
+ double cycle_gap_avg = _cycle_gap_history->avg();
+ double conc_mark_avg = _conc_mark_duration_history->avg();
+ double conc_uprefs_avg = _conc_uprefs_duration_history->avg();
+
+ if (_update_refs_early) {
+ double threshold = ShenandoahMergeUpdateRefsMinGap / 100.0;
+ if (conc_mark_avg + conc_uprefs_avg > cycle_gap_avg * threshold) {
+ _update_refs_early = false;
+ }
+ } else {
+ double threshold = ShenandoahMergeUpdateRefsMaxGap / 100.0;
+ if (conc_mark_avg + conc_uprefs_avg < cycle_gap_avg * threshold) {
+ _update_refs_early = true;
+ }
+ }
+ return _update_refs_early;
+}
+
+const char* ShenandoahAdaptiveHeuristics::name() {
+ return "adaptive";
+}
+
+bool ShenandoahAdaptiveHeuristics::is_diagnostic() {
+ return false;
+}
+
+bool ShenandoahAdaptiveHeuristics::is_experimental() {
+ return false;
+}