1/*
2 * Copyright (c) 2018, Red Hat, Inc. All rights reserved.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This code is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
11 * version 2 for more details (a copy is included in the LICENSE file that
12 * accompanied this code).
13 *
14 * You should have received a copy of the GNU General Public License version
15 * 2 along with this work; if not, write to the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17 *
18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19 * or visit www.oracle.com if you need additional information or have any
20 * questions.
21 *
22 */
23
24#include "precompiled.hpp"
25
26#include "gc/shenandoah/heuristics/shenandoahPassiveHeuristics.hpp"
27#include "gc/shenandoah/shenandoahCollectionSet.hpp"
28#include "gc/shenandoah/shenandoahHeapRegion.hpp"
29#include "logging/log.hpp"
30#include "logging/logTag.hpp"
31
32ShenandoahPassiveHeuristics::ShenandoahPassiveHeuristics() : ShenandoahHeuristics() {
33 // Do not allow concurrent cycles.
34 FLAG_SET_DEFAULT(ExplicitGCInvokesConcurrent, false);
35 FLAG_SET_DEFAULT(ShenandoahImplicitGCInvokesConcurrent, false);
36
37 // Passive runs with max speed, reacts on allocation failure.
38 FLAG_SET_DEFAULT(ShenandoahPacing, false);
39
40 // No need for evacuation reserve with Full GC, only for Degenerated GC.
41 if (!ShenandoahDegeneratedGC) {
42 SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahEvacReserve, 0);
43 }
44
45 // Disable known barriers by default.
46 SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahLoadRefBarrier);
47 SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahSATBBarrier);
48 SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahKeepAliveBarrier);
49 SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahStoreValEnqueueBarrier);
50 SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahCASBarrier);
51 SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahCloneBarrier);
52
53 // Final configuration checks
54 // No barriers are required to run.
55}
56
57bool ShenandoahPassiveHeuristics::should_start_normal_gc() const {
58 // Never do concurrent GCs.
59 return false;
60}
61
62bool ShenandoahPassiveHeuristics::should_process_references() {
63 // Always process references, if we can.
64 return can_process_references();
65}
66
67bool ShenandoahPassiveHeuristics::should_unload_classes() {
68 // Always unload classes, if we can.
69 return can_unload_classes();
70}
71
72bool ShenandoahPassiveHeuristics::should_degenerate_cycle() {
73 // Always fail to Degenerated GC, if enabled
74 return ShenandoahDegeneratedGC;
75}
76
77void ShenandoahPassiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
78 RegionData* data, size_t size,
79 size_t actual_free) {
80 assert(ShenandoahDegeneratedGC, "This path is only taken for Degenerated GC");
81
82 // Do not select too large CSet that would overflow the available free space.
83 // Take at least the entire evacuation reserve, and be free to overflow to free space.
84 size_t capacity = ShenandoahHeap::heap()->max_capacity();
85 size_t available = MAX2(capacity / 100 * ShenandoahEvacReserve, actual_free);
86 size_t max_cset = (size_t)(available / ShenandoahEvacWaste);
87
88 log_info(gc, ergo)("CSet Selection. Actual Free: " SIZE_FORMAT "M, Max CSet: " SIZE_FORMAT "M",
89 actual_free / M, max_cset / M);
90
91 size_t threshold = ShenandoahHeapRegion::region_size_bytes() * ShenandoahGarbageThreshold / 100;
92
93 size_t live_cset = 0;
94 for (size_t idx = 0; idx < size; idx++) {
95 ShenandoahHeapRegion* r = data[idx]._region;
96 size_t new_cset = live_cset + r->get_live_data_bytes();
97 if (new_cset < max_cset && r->garbage() > threshold) {
98 live_cset = new_cset;
99 cset->add_region(r);
100 }
101 }
102}
103
104const char* ShenandoahPassiveHeuristics::name() {
105 return "passive";
106}
107
108bool ShenandoahPassiveHeuristics::is_diagnostic() {
109 return true;
110}
111
112bool ShenandoahPassiveHeuristics::is_experimental() {
113 return false;
114}
115