1 /*
 2  * Copyright (c) 2017, Red Hat, Inc. and/or its affiliates.
 3  * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
 4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 5  *
 6  * This code is free software; you can redistribute it and/or modify it
 7  * under the terms of the GNU General Public License version 2 only, as
 8  * published by the Free Software Foundation.
 9  *
10  * This code is distributed in the hope that it will be useful, but WITHOUT
11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
13  * version 2 for more details (a copy is included in the LICENSE file that
14  * accompanied this code).
15  *
16  * You should have received a copy of the GNU General Public License version
17  * 2 along with this work; if not, write to the Free Software Foundation,
18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19  *
20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21  * or visit www.oracle.com if you need additional information or have any
22  * questions.
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24  */
25 
26 #include "gc/serial/serialArguments.hpp"
27 #include "gc/serial/serialHeap.hpp"
28 #include "gc/shared/fullGCForwarding.hpp"
29 #include "gc/shared/gcArguments.hpp"
30 
31 static size_t compute_heap_alignment() {
32   // The card marking array and the offset arrays for old generations are
33   // committed in os pages as well. Make sure they are entirely full (to
34   // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
35   // byte entry and the os page size is 4096, the maximum heap size should
36   // be 512*4096 = 2MB aligned.
37 
38   size_t alignment = CardTable::ct_max_alignment_constraint();
39 
40   if (UseLargePages) {
41       // In presence of large pages we have to make sure that our
42       // alignment is large page aware.
43       alignment = lcm(os::large_page_size(), alignment);
44   }
45 
46   return alignment;
47 }
48 
49 void SerialArguments::initialize_alignments() {
50   // Initialize card size before initializing alignments
51   CardTable::initialize_card_size();
52   SpaceAlignment = (size_t)Generation::GenGrain;
53   HeapAlignment = compute_heap_alignment();
54 }
55 
56 void SerialArguments::initialize() {
57   GCArguments::initialize();
58   FullGCForwarding::initialize_flags(MaxHeapSize);
59 }
60 
61 size_t SerialArguments::conservative_max_heap_alignment() {
62   return MAX2((size_t)Generation::GenGrain, compute_heap_alignment());
63 }
64 
65 CollectedHeap* SerialArguments::create_heap() {
66   return new SerialHeap();
67 }
68 
69 size_t SerialArguments::young_gen_size_lower_bound() {
70   // The young generation must be aligned and have room for eden + two survivors
71   return 3 * SpaceAlignment;
72 }
73 
74 size_t SerialArguments::old_gen_size_lower_bound() {
75   return SpaceAlignment;
76 }