1 /*
 2  * Copyright (c) 2019, 2021, Oracle and/or its affiliates. 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 #include "precompiled.hpp"
25 #include "gc/z/zThreadLocalData.hpp"
26 #include "gc/z/zObjArrayAllocator.hpp"
27 #include "gc/z/zUtils.inline.hpp"
28 #include "oops/arrayKlass.hpp"
29 #include "runtime/interfaceSupport.inline.hpp"
30 
31 ZObjArrayAllocator::ZObjArrayAllocator(Klass* klass, size_t word_size, int length, Thread* thread) :
32     ObjArrayAllocator(klass, word_size, length, false /* do_zero */, thread) {}
33 
34 oop ZObjArrayAllocator::finish(HeapWord* mem) const {
35   // Initialize object header and length field
36   ObjArrayAllocator::finish(mem);
37 
38   // Keep the array alive across safepoints through an invisible
39   // root. Invisible roots are not visited by the heap itarator
40   // and the marking logic will not attempt to follow its elements.
41   ZThreadLocalData::set_invisible_root(_thread, (oop*)&mem);
42 
43   // A max segment size of 64K was chosen because microbenchmarking
44   // suggested that it offered a good trade-off between allocation
45   // time and time-to-safepoint
46   const size_t segment_max = ZUtils::bytes_to_words(64 * K);
47   const size_t skip = arrayOopDesc::header_size(ArrayKlass::cast(_klass)->element_type());
48   size_t remaining = _word_size - skip;
49 
50   while (remaining > 0) {
51     // Clear segment
52     const size_t segment = MIN2(remaining, segment_max);
53     Copy::zero_to_words(mem + (_word_size - remaining), segment);
54     remaining -= segment;
55 
56     if (remaining > 0) {
57       // Safepoint
58       ThreadBlockInVM tbivm(JavaThread::cast(_thread));
59     }
60   }
61 
62   ZThreadLocalData::clear_invisible_root(_thread);
63 
64   return cast_to_oop(mem);
65 }