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/shenandoahPassiveHeuristics.hpp"
28 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
29 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
30 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
31 #include "logging/log.hpp"
32 #include "logging/logTag.hpp"
33 
34 bool ShenandoahPassiveHeuristics::should_start_gc() {
35   // Never do concurrent GCs.
36   return false;
37 }
38 
39 bool ShenandoahPassiveHeuristics::should_unload_classes() {
40   // Always unload classes, if we can.
41   return can_unload_classes();
42 }
43 
44 bool ShenandoahPassiveHeuristics::should_degenerate_cycle() {
45   // Always fail to Degenerated GC, if enabled
46   return ShenandoahDegeneratedGC;
47 }
48 
49 void ShenandoahPassiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
50                                                                         RegionData* data, size_t size,
51                                                                         size_t actual_free) {
52   assert(ShenandoahDegeneratedGC, "This path is only taken for Degenerated GC");
53 
54   // Do not select too large CSet that would overflow the available free space.
55   // Take at least the entire evacuation reserve, and be free to overflow to free space.
56   size_t max_capacity = ShenandoahHeap::heap()->max_capacity();
57   size_t available = MAX2((max_capacity / 100) * ShenandoahEvacReserve, actual_free);
58   size_t max_cset  = (size_t)(available / ShenandoahEvacWaste);
59 
60   log_info(gc, ergo)("CSet Selection. Actual Free: " SIZE_FORMAT "%s, Max CSet: " SIZE_FORMAT "%s",
61                      byte_size_in_proper_unit(actual_free), proper_unit_for_byte_size(actual_free),
62                      byte_size_in_proper_unit(max_cset),    proper_unit_for_byte_size(max_cset));
63 
64   size_t threshold = ShenandoahHeapRegion::region_size_bytes() * ShenandoahGarbageThreshold / 100;
65 
66   size_t live_cset = 0;
67   for (size_t idx = 0; idx < size; idx++) {
68     ShenandoahHeapRegion* r = data[idx]._region;
69     size_t new_cset = live_cset + r->get_live_data_bytes();
70     if (new_cset < max_cset && r->garbage() > threshold) {
71       live_cset = new_cset;
72       cset->add_region(r);
73     }
74   }
75 }