--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/g1/g1HeapSizingPolicy.cpp Fri Mar 11 11:22:56 2016 +0100
@@ -0,0 +1,157 @@
+/*
+ * Copyright (c) 2016, 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/g1/g1CollectedHeap.hpp"
+#include "gc/g1/g1HeapSizingPolicy.hpp"
+#include "gc/g1/g1Analytics.hpp"
+#include "logging/log.hpp"
+#include "runtime/globals.hpp"
+#include "utilities/debug.hpp"
+#include "utilities/globalDefinitions.hpp"
+
+G1HeapSizingPolicy::G1HeapSizingPolicy(const G1CollectedHeap* g1, const G1Analytics* analytics) :
+ _g1(g1),
+ _analytics(analytics),
+ _num_prev_pauses_for_heuristics(analytics->number_of_recorded_pause_times()) {
+ assert(MinOverThresholdForGrowth < _num_prev_pauses_for_heuristics, "Threshold must be less than %u", _num_prev_pauses_for_heuristics);
+ clear_ratio_check_data();
+ }
+
+void G1HeapSizingPolicy::clear_ratio_check_data() {
+ _ratio_over_threshold_count = 0;
+ _ratio_over_threshold_sum = 0.0;
+ _pauses_since_start = 0;
+}
+
+size_t G1HeapSizingPolicy::expansion_amount() {
+ double recent_gc_overhead = _analytics->recent_avg_pause_time_ratio() * 100.0;
+ double last_gc_overhead = _analytics->last_pause_time_ratio() * 100.0;
+ assert(GCTimeRatio > 0,
+ "we should have set it to a default value set_g1_gc_flags() "
+ "if a user set it to 0");
+ const double gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio));
+
+ double threshold = gc_overhead_perc;
+ size_t expand_bytes = 0;
+
+ // If the heap is at less than half its maximum size, scale the threshold down,
+ // to a limit of 1. Thus the smaller the heap is, the more likely it is to expand,
+ // though the scaling code will likely keep the increase small.
+ if (_g1->capacity() <= _g1->max_capacity() / 2) {
+ threshold *= (double)_g1->capacity() / (double)(_g1->max_capacity() / 2);
+ threshold = MAX2(threshold, 1.0);
+ }
+
+ // If the last GC time ratio is over the threshold, increment the count of
+ // times it has been exceeded, and add this ratio to the sum of exceeded
+ // ratios.
+ if (last_gc_overhead > threshold) {
+ _ratio_over_threshold_count++;
+ _ratio_over_threshold_sum += last_gc_overhead;
+ }
+
+ // Check if we've had enough GC time ratio checks that were over the
+ // threshold to trigger an expansion. We'll also expand if we've
+ // reached the end of the history buffer and the average of all entries
+ // is still over the threshold. This indicates a smaller number of GCs were
+ // long enough to make the average exceed the threshold.
+ bool filled_history_buffer = _pauses_since_start == _num_prev_pauses_for_heuristics;
+ if ((_ratio_over_threshold_count == MinOverThresholdForGrowth) ||
+ (filled_history_buffer && (recent_gc_overhead > threshold))) {
+ size_t min_expand_bytes = HeapRegion::GrainBytes;
+ size_t reserved_bytes = _g1->max_capacity();
+ size_t committed_bytes = _g1->capacity();
+ size_t uncommitted_bytes = reserved_bytes - committed_bytes;
+ size_t expand_bytes_via_pct =
+ uncommitted_bytes * G1ExpandByPercentOfAvailable / 100;
+ double scale_factor = 1.0;
+
+ // If the current size is less than 1/4 of the Initial heap size, expand
+ // by half of the delta between the current and Initial sizes. IE, grow
+ // back quickly.
+ //
+ // Otherwise, take the current size, or G1ExpandByPercentOfAvailable % of
+ // the available expansion space, whichever is smaller, as the base
+ // expansion size. Then possibly scale this size according to how much the
+ // threshold has (on average) been exceeded by. If the delta is small
+ // (less than the StartScaleDownAt value), scale the size down linearly, but
+ // not by less than MinScaleDownFactor. If the delta is large (greater than
+ // the StartScaleUpAt value), scale up, but adding no more than MaxScaleUpFactor
+ // times the base size. The scaling will be linear in the range from
+ // StartScaleUpAt to (StartScaleUpAt + ScaleUpRange). In other words,
+ // ScaleUpRange sets the rate of scaling up.
+ if (committed_bytes < InitialHeapSize / 4) {
+ expand_bytes = (InitialHeapSize - committed_bytes) / 2;
+ } else {
+ double const MinScaleDownFactor = 0.2;
+ double const MaxScaleUpFactor = 2;
+ double const StartScaleDownAt = gc_overhead_perc;
+ double const StartScaleUpAt = gc_overhead_perc * 1.5;
+ double const ScaleUpRange = gc_overhead_perc * 2.0;
+
+ double ratio_delta;
+ if (filled_history_buffer) {
+ ratio_delta = recent_gc_overhead - threshold;
+ } else {
+ ratio_delta = (_ratio_over_threshold_sum/_ratio_over_threshold_count) - threshold;
+ }
+
+ expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes);
+ if (ratio_delta < StartScaleDownAt) {
+ scale_factor = ratio_delta / StartScaleDownAt;
+ scale_factor = MAX2(scale_factor, MinScaleDownFactor);
+ } else if (ratio_delta > StartScaleUpAt) {
+ scale_factor = 1 + ((ratio_delta - StartScaleUpAt) / ScaleUpRange);
+ scale_factor = MIN2(scale_factor, MaxScaleUpFactor);
+ }
+ }
+
+ log_debug(gc, ergo, heap)("Attempt heap expansion (recent GC overhead higher than threshold after GC) "
+ "recent GC overhead: %1.2f %% threshold: %1.2f %% uncommitted: " SIZE_FORMAT "B base expansion amount and scale: " SIZE_FORMAT "B (%1.2f%%)",
+ recent_gc_overhead, threshold, uncommitted_bytes, expand_bytes, scale_factor * 100);
+
+ expand_bytes = static_cast<size_t>(expand_bytes * scale_factor);
+
+ // Ensure the expansion size is at least the minimum growth amount
+ // and at most the remaining uncommitted byte size.
+ expand_bytes = MAX2(expand_bytes, min_expand_bytes);
+ expand_bytes = MIN2(expand_bytes, uncommitted_bytes);
+
+ clear_ratio_check_data();
+ } else {
+ // An expansion was not triggered. If we've started counting, increment
+ // the number of checks we've made in the current window. If we've
+ // reached the end of the window without resizing, clear the counters to
+ // start again the next time we see a ratio above the threshold.
+ if (_ratio_over_threshold_count > 0) {
+ _pauses_since_start++;
+ if (_pauses_since_start > _num_prev_pauses_for_heuristics) {
+ clear_ratio_check_data();
+ }
+ }
+ }
+
+ return expand_bytes;
+}