1 /*
 2  * Copyright (c) 2018, 2019, Red Hat, Inc. All rights reserved.
 3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 4  *
 5  * This code is free software; you can redistribute it and/or modify it
 6  * under the terms of the GNU General Public License version 2 only, as
 7  * published by the Free Software Foundation.
 8  *
 9  * This code is distributed in the hope that it will be useful, but WITHOUT
10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12  * version 2 for more details (a copy is included in the LICENSE file that
13  * accompanied this code).
14  *
15  * You should have received a copy of the GNU General Public License version
16  * 2 along with this work; if not, write to the Free Software Foundation,
17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18  *
19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20  * or visit www.oracle.com if you need additional information or have any
21  * questions.
22  *
23  */
24 
25 #include "precompiled.hpp"
26 
27 #include "gc/shenandoah/heuristics/shenandoahAggressiveHeuristics.hpp"
28 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
29 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
30 #include "logging/log.hpp"
31 #include "logging/logTag.hpp"
32 #include "runtime/os.hpp"
33 
34 ShenandoahAggressiveHeuristics::ShenandoahAggressiveHeuristics(ShenandoahGeneration* generation) : ShenandoahHeuristics(generation) {
35   // Do not shortcut evacuation
36   SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahImmediateThreshold, 100);
37 
38   // Aggressive evacuates everything, so it needs as much evac space as it can get
39   SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahEvacReserveOverflow);
40 
41   // If class unloading is globally enabled, aggressive does unloading even with
42   // concurrent cycles.
43   if (ClassUnloading) {
44     SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahUnloadClassesFrequency, 1);
45   }
46 }
47 
48 void ShenandoahAggressiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
49                                                                            RegionData* data, size_t size,
50                                                                            size_t free) {
51   assert(!ShenandoahHeap::heap()->mode()->is_generational(), "AggressiveHeuristics not appropriate in generational mode");
52 
53   // Note that there's no bound on collection set size.  If we try to collect too much memory, we'll get an alloc
54   // failure during collection and we'll degenerate.
55   for (size_t idx = 0; idx < size; idx++) {
56     ShenandoahHeapRegion* r = data[idx]._region;
57     if (r->garbage() > 0) {
58       cset->add_region(r);
59     }
60   }
61 }
62 
63 bool ShenandoahAggressiveHeuristics::should_start_gc() {
64   log_info(gc)("Trigger: Start next cycle immediately");
65   return true;
66 }
67 
68 bool ShenandoahAggressiveHeuristics::should_unload_classes() {
69   if (!can_unload_classes_normal()) return false;
70   if (has_metaspace_oom()) return true;
71   // Randomly unload classes with 50% chance.
72   return (os::random() & 1) == 1;
73 }
--- EOF ---