1/*
2 * Copyright (c) 2014, 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#ifndef SHARE_GC_SHENANDOAH_SHENANDOAHMARKCOMPACT_HPP
25#define SHARE_GC_SHENANDOAH_SHENANDOAHMARKCOMPACT_HPP
26
27#include "gc/shared/gcTimer.hpp"
28#include "gc/shenandoah/shenandoahHeap.hpp"
29#include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
30
31/**
32 * This implements Full GC (e.g. when invoking System.gc()) using a mark-compact algorithm.
33 *
34 * Current implementation is parallel sliding Lisp-2-style algorithm, based on
35 * "Parallel Garbage Collection for Shared Memory Multiprocessors", by Christine Flood et al.
36 * http://people.csail.mit.edu/shanir/publications/dfsz2001.pdf
37 *
38 * It is implemented in four phases:
39 *
40 * 1. Mark all live objects of the heap by traversing objects starting at GC roots.
41 * 2. Calculate the new location of each live object. This is done by sequentially scanning
42 * the heap, keeping track of a next-location-pointer, which is then written to each
43 * object's fwdptr field.
44 * 3. Update all references. This is implemented by another scan of the heap, and updates
45 * all references in live objects by what's stored in the target object's fwdptr.
46 * 4. Compact the heap by copying all live objects to their new location.
47 *
48 * Parallelization is handled by assigning each GC worker the slice of the heap (the set of regions)
49 * where it does sliding compaction, without interfering with other threads.
50 */
51
52class PreservedMarksSet;
53
54class ShenandoahMarkCompact : public CHeapObj<mtGC> {
55 friend class ShenandoahPrepareForCompactionObjectClosure;
56private:
57 GCTimer* _gc_timer;
58
59 PreservedMarksSet* _preserved_marks;
60
61public:
62 ShenandoahMarkCompact();
63 void initialize(GCTimer* gc_timer);
64
65 void do_it(GCCause::Cause gc_cause);
66
67private:
68 void phase1_mark_heap();
69 void phase2_calculate_target_addresses(ShenandoahHeapRegionSet** worker_slices);
70 void phase3_update_references();
71 void phase4_compact_objects(ShenandoahHeapRegionSet** worker_slices);
72
73 void calculate_target_humongous_objects();
74 void compact_humongous_objects();
75};
76
77#endif // SHARE_GC_SHENANDOAH_SHENANDOAHMARKCOMPACT_HPP
78