--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/g1/g1CollectionSet.cpp Mon Mar 07 17:23:59 2016 +0100
@@ -0,0 +1,426 @@
+/*
+ * 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/g1CollectionSet.hpp"
+#include "gc/g1/g1CollectorPolicy.hpp"
+#include "gc/g1/g1CollectorState.hpp"
+#include "gc/g1/heapRegion.inline.hpp"
+#include "gc/g1/heapRegionRemSet.hpp"
+#include "gc/g1/heapRegionSet.hpp"
+#include "utilities/debug.hpp"
+
+G1CollectorState* G1CollectionSet::collector_state() {
+ return _g1->collector_state();
+}
+
+G1GCPhaseTimes* G1CollectionSet::phase_times() {
+ return _policy->phase_times();
+}
+
+CollectionSetChooser* G1CollectionSet::cset_chooser() {
+ return _cset_chooser;
+}
+
+double G1CollectionSet::predict_region_elapsed_time_ms(HeapRegion* hr) {
+ return _policy->predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
+}
+
+
+G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h) :
+ _g1(g1h),
+ _policy(NULL),
+ _cset_chooser(new CollectionSetChooser()),
+ _eden_region_length(0),
+ _survivor_region_length(0),
+ _old_region_length(0),
+
+ _head(NULL),
+ _bytes_used_before(0),
+ _recorded_rs_lengths(0),
+ // Incremental CSet attributes
+ _inc_build_state(Inactive),
+ _inc_head(NULL),
+ _inc_tail(NULL),
+ _inc_bytes_used_before(0),
+ _inc_recorded_rs_lengths(0),
+ _inc_recorded_rs_lengths_diffs(0),
+ _inc_predicted_elapsed_time_ms(0.0),
+ _inc_predicted_elapsed_time_ms_diffs(0.0) {}
+
+G1CollectionSet::~G1CollectionSet() {
+ delete _cset_chooser;
+}
+
+void G1CollectionSet::init_region_lengths(uint eden_cset_region_length,
+ uint survivor_cset_region_length) {
+ _eden_region_length = eden_cset_region_length;
+ _survivor_region_length = survivor_cset_region_length;
+ _old_region_length = 0;
+}
+
+void G1CollectionSet::set_recorded_rs_lengths(size_t rs_lengths) {
+ _recorded_rs_lengths = rs_lengths;
+}
+
+// Add the heap region at the head of the non-incremental collection set
+void G1CollectionSet::add_old_region(HeapRegion* hr) {
+ assert(_inc_build_state == Active, "Precondition");
+ assert(hr->is_old(), "the region should be old");
+
+ assert(!hr->in_collection_set(), "should not already be in the CSet");
+ _g1->register_old_region_with_cset(hr);
+ hr->set_next_in_collection_set(_head);
+ _head = hr;
+ _bytes_used_before += hr->used();
+ size_t rs_length = hr->rem_set()->occupied();
+ _recorded_rs_lengths += rs_length;
+ _old_region_length += 1;
+}
+
+// Initialize the per-collection-set information
+void G1CollectionSet::start_incremental_building() {
+ assert(_inc_build_state == Inactive, "Precondition");
+
+ _inc_head = NULL;
+ _inc_tail = NULL;
+ _inc_bytes_used_before = 0;
+
+ _inc_recorded_rs_lengths = 0;
+ _inc_recorded_rs_lengths_diffs = 0;
+ _inc_predicted_elapsed_time_ms = 0.0;
+ _inc_predicted_elapsed_time_ms_diffs = 0.0;
+ _inc_build_state = Active;
+}
+
+void G1CollectionSet::finalize_incremental_building() {
+ assert(_inc_build_state == Active, "Precondition");
+ assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
+
+ // The two "main" fields, _inc_recorded_rs_lengths and
+ // _inc_predicted_elapsed_time_ms, are updated by the thread
+ // that adds a new region to the CSet. Further updates by the
+ // concurrent refinement thread that samples the young RSet lengths
+ // are accumulated in the *_diffs fields. Here we add the diffs to
+ // the "main" fields.
+
+ if (_inc_recorded_rs_lengths_diffs >= 0) {
+ _inc_recorded_rs_lengths += _inc_recorded_rs_lengths_diffs;
+ } else {
+ // This is defensive. The diff should in theory be always positive
+ // as RSets can only grow between GCs. However, given that we
+ // sample their size concurrently with other threads updating them
+ // it's possible that we might get the wrong size back, which
+ // could make the calculations somewhat inaccurate.
+ size_t diffs = (size_t) (-_inc_recorded_rs_lengths_diffs);
+ if (_inc_recorded_rs_lengths >= diffs) {
+ _inc_recorded_rs_lengths -= diffs;
+ } else {
+ _inc_recorded_rs_lengths = 0;
+ }
+ }
+ _inc_predicted_elapsed_time_ms += _inc_predicted_elapsed_time_ms_diffs;
+
+ _inc_recorded_rs_lengths_diffs = 0;
+ _inc_predicted_elapsed_time_ms_diffs = 0.0;
+}
+
+void G1CollectionSet::update_young_region_prediction(HeapRegion* hr,
+ size_t new_rs_length) {
+ // Update the CSet information that is dependent on the new RS length
+ assert(hr->is_young(), "Precondition");
+ assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint");
+
+ // We could have updated _inc_recorded_rs_lengths and
+ // _inc_predicted_elapsed_time_ms directly but we'd need to do
+ // that atomically, as this code is executed by a concurrent
+ // refinement thread, potentially concurrently with a mutator thread
+ // allocating a new region and also updating the same fields. To
+ // avoid the atomic operations we accumulate these updates on two
+ // separate fields (*_diffs) and we'll just add them to the "main"
+ // fields at the start of a GC.
+
+ ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
+ ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length;
+ _inc_recorded_rs_lengths_diffs += rs_lengths_diff;
+
+ double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
+ double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
+ double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
+ _inc_predicted_elapsed_time_ms_diffs += elapsed_ms_diff;
+
+ hr->set_recorded_rs_length(new_rs_length);
+ hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
+}
+
+void G1CollectionSet::add_young_region_common(HeapRegion* hr) {
+ assert(hr->is_young(), "invariant");
+ assert(hr->young_index_in_cset() > -1, "should have already been set");
+ assert(_inc_build_state == Active, "Precondition");
+
+ // This routine is used when:
+ // * adding survivor regions to the incremental cset at the end of an
+ // evacuation pause or
+ // * adding the current allocation region to the incremental cset
+ // when it is retired.
+ // Therefore this routine may be called at a safepoint by the
+ // VM thread, or in-between safepoints by mutator threads (when
+ // retiring the current allocation region)
+ // We need to clear and set the cached recorded/cached collection set
+ // information in the heap region here (before the region gets added
+ // to the collection set). An individual heap region's cached values
+ // are calculated, aggregated with the policy collection set info,
+ // and cached in the heap region here (initially) and (subsequently)
+ // by the Young List sampling code.
+
+ size_t rs_length = hr->rem_set()->occupied();
+ double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
+
+ // Cache the values we have added to the aggregated information
+ // in the heap region in case we have to remove this region from
+ // the incremental collection set, or it is updated by the
+ // rset sampling code
+ hr->set_recorded_rs_length(rs_length);
+ hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
+
+ size_t used_bytes = hr->used();
+ _inc_recorded_rs_lengths += rs_length;
+ _inc_predicted_elapsed_time_ms += region_elapsed_time_ms;
+ _inc_bytes_used_before += used_bytes;
+
+ assert(!hr->in_collection_set(), "invariant");
+ _g1->register_young_region_with_cset(hr);
+ assert(hr->next_in_collection_set() == NULL, "invariant");
+}
+
+// Add the region at the RHS of the incremental cset
+void G1CollectionSet::add_survivor_regions(HeapRegion* hr) {
+ // We should only ever be appending survivors at the end of a pause
+ assert(hr->is_survivor(), "Logic");
+
+ // Do the 'common' stuff
+ add_young_region_common(hr);
+
+ // Now add the region at the right hand side
+ if (_inc_tail == NULL) {
+ assert(_inc_head == NULL, "invariant");
+ _inc_head = hr;
+ } else {
+ _inc_tail->set_next_in_collection_set(hr);
+ }
+ _inc_tail = hr;
+}
+
+// Add the region to the LHS of the incremental cset
+void G1CollectionSet::add_eden_region(HeapRegion* hr) {
+ // Survivors should be added to the RHS at the end of a pause
+ assert(hr->is_eden(), "Logic");
+
+ // Do the 'common' stuff
+ add_young_region_common(hr);
+
+ // Add the region at the left hand side
+ hr->set_next_in_collection_set(_inc_head);
+ if (_inc_head == NULL) {
+ assert(_inc_tail == NULL, "Invariant");
+ _inc_tail = hr;
+ }
+ _inc_head = hr;
+}
+
+#ifndef PRODUCT
+void G1CollectionSet::print(HeapRegion* list_head, outputStream* st) {
+ assert(list_head == inc_head() || list_head == head(), "must be");
+
+ st->print_cr("\nCollection_set:");
+ HeapRegion* csr = list_head;
+ while (csr != NULL) {
+ HeapRegion* next = csr->next_in_collection_set();
+ assert(csr->in_collection_set(), "bad CS");
+ st->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
+ HR_FORMAT_PARAMS(csr),
+ p2i(csr->prev_top_at_mark_start()), p2i(csr->next_top_at_mark_start()),
+ csr->age_in_surv_rate_group_cond());
+ csr = next;
+ }
+}
+#endif // !PRODUCT
+
+double G1CollectionSet::finalize_young_part(double target_pause_time_ms) {
+ double young_start_time_sec = os::elapsedTime();
+
+ YoungList* young_list = _g1->young_list();
+ finalize_incremental_building();
+
+ guarantee(target_pause_time_ms > 0.0,
+ "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
+ guarantee(_head == NULL, "Precondition");
+
+ size_t pending_cards = _policy->pending_cards();
+ double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards);
+ double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
+
+ log_trace(gc, ergo, cset)("Start choosing CSet. pending cards: " SIZE_FORMAT " predicted base time: %1.2fms remaining time: %1.2fms target pause time: %1.2fms",
+ pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
+
+ collector_state()->set_last_gc_was_young(collector_state()->gcs_are_young());
+
+ // The young list is laid with the survivor regions from the previous
+ // pause are appended to the RHS of the young list, i.e.
+ // [Newly Young Regions ++ Survivors from last pause].
+
+ uint survivor_region_length = young_list->survivor_length();
+ uint eden_region_length = young_list->eden_length();
+ init_region_lengths(eden_region_length, survivor_region_length);
+
+ HeapRegion* hr = young_list->first_survivor_region();
+ while (hr != NULL) {
+ assert(hr->is_survivor(), "badly formed young list");
+ // There is a convention that all the young regions in the CSet
+ // are tagged as "eden", so we do this for the survivors here. We
+ // use the special set_eden_pre_gc() as it doesn't check that the
+ // region is free (which is not the case here).
+ hr->set_eden_pre_gc();
+ hr = hr->get_next_young_region();
+ }
+
+ // Clear the fields that point to the survivor list - they are all young now.
+ young_list->clear_survivors();
+
+ _head = _inc_head;
+ _bytes_used_before = _inc_bytes_used_before;
+ time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0);
+
+ log_trace(gc, ergo, cset)("Add young regions to CSet. eden: %u regions, survivors: %u regions, predicted young region time: %1.2fms, target pause time: %1.2fms",
+ eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms);
+
+ // The number of recorded young regions is the incremental
+ // collection set's current size
+ set_recorded_rs_lengths(_inc_recorded_rs_lengths);
+
+ double young_end_time_sec = os::elapsedTime();
+ phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
+
+ return time_remaining_ms;
+}
+
+void G1CollectionSet::finalize_old_part(double time_remaining_ms) {
+ double non_young_start_time_sec = os::elapsedTime();
+ double predicted_old_time_ms = 0.0;
+
+ if (!collector_state()->gcs_are_young()) {
+ cset_chooser()->verify();
+ const uint min_old_cset_length = _policy->calc_min_old_cset_length();
+ const uint max_old_cset_length = _policy->calc_max_old_cset_length();
+
+ uint expensive_region_num = 0;
+ bool check_time_remaining = _policy->adaptive_young_list_length();
+
+ HeapRegion* hr = cset_chooser()->peek();
+ while (hr != NULL) {
+ if (old_region_length() >= max_old_cset_length) {
+ // Added maximum number of old regions to the CSet.
+ log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached max). old %u regions, max %u regions",
+ old_region_length(), max_old_cset_length);
+ break;
+ }
+
+ // Stop adding regions if the remaining reclaimable space is
+ // not above G1HeapWastePercent.
+ size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
+ double reclaimable_perc = _policy->reclaimable_bytes_perc(reclaimable_bytes);
+ double threshold = (double) G1HeapWastePercent;
+ if (reclaimable_perc <= threshold) {
+ // We've added enough old regions that the amount of uncollected
+ // reclaimable space is at or below the waste threshold. Stop
+ // adding old regions to the CSet.
+ log_debug(gc, ergo, cset)("Finish adding old regions to CSet (reclaimable percentage not over threshold). "
+ "old %u regions, max %u regions, reclaimable: " SIZE_FORMAT "B (%1.2f%%) threshold: " UINTX_FORMAT "%%",
+ old_region_length(), max_old_cset_length, reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
+ break;
+ }
+
+ double predicted_time_ms = predict_region_elapsed_time_ms(hr);
+ if (check_time_remaining) {
+ if (predicted_time_ms > time_remaining_ms) {
+ // Too expensive for the current CSet.
+
+ if (old_region_length() >= min_old_cset_length) {
+ // We have added the minimum number of old regions to the CSet,
+ // we are done with this CSet.
+ log_debug(gc, ergo, cset)("Finish adding old regions to CSet (predicted time is too high). "
+ "predicted time: %1.2fms, remaining time: %1.2fms old %u regions, min %u regions",
+ predicted_time_ms, time_remaining_ms, old_region_length(), min_old_cset_length);
+ break;
+ }
+
+ // We'll add it anyway given that we haven't reached the
+ // minimum number of old regions.
+ expensive_region_num += 1;
+ }
+ } else {
+ if (old_region_length() >= min_old_cset_length) {
+ // In the non-auto-tuning case, we'll finish adding regions
+ // to the CSet if we reach the minimum.
+
+ log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached min). old %u regions, min %u regions",
+ old_region_length(), min_old_cset_length);
+ break;
+ }
+ }
+
+ // We will add this region to the CSet.
+ time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
+ predicted_old_time_ms += predicted_time_ms;
+ cset_chooser()->pop(); // already have region via peek()
+ _g1->old_set_remove(hr);
+ add_old_region(hr);
+
+ hr = cset_chooser()->peek();
+ }
+ if (hr == NULL) {
+ log_debug(gc, ergo, cset)("Finish adding old regions to CSet (candidate old regions not available)");
+ }
+
+ if (expensive_region_num > 0) {
+ // We print the information once here at the end, predicated on
+ // whether we added any apparently expensive regions or not, to
+ // avoid generating output per region.
+ log_debug(gc, ergo, cset)("Added expensive regions to CSet (old CSet region num not reached min)."
+ "old: %u regions, expensive: %u regions, min: %u regions, remaining time: %1.2fms",
+ old_region_length(), expensive_region_num, min_old_cset_length, time_remaining_ms);
+ }
+
+ cset_chooser()->verify();
+ }
+
+ stop_incremental_building();
+
+ log_debug(gc, ergo, cset)("Finish choosing CSet. old: %u regions, predicted old region time: %1.2fms, time remaining: %1.2f",
+ old_region_length(), predicted_old_time_ms, time_remaining_ms);
+
+ double non_young_end_time_sec = os::elapsedTime();
+ phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
+}