1 /* 2 * Copyright (c) 2019, 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/zObjArrayAllocator.hpp" 26 #include "gc/z/zUtils.inline.hpp" 27 #include "memory/universe.hpp" 28 #include "oops/arrayKlass.hpp" 29 #include "runtime/interfaceSupport.inline.hpp" 30 #include "runtime/handles.hpp" 31 #include "runtime/os.hpp" 32 #include "utilities/globalDefinitions.hpp" 33 34 // To avoid delaying safepoints, clearing of arrays is split up in segments 35 // with safepoint polling inbetween. However, we can't have a not-yet-cleared 36 // array of oops on the heap when we safepoint since the GC will then stumble 37 // across uninitialized oops. To avoid this we let an array of oops be an 38 // array of longs until the clearing has completed. We use longs as substitue 39 // for oops because they have the same size and alignment when using ZGC (i.e. 40 // compressed oops is disabled). A max segment size of 64K was chosen because 41 // it offers a good trade-off between allocation time and time-to-safepoint. 42 43 static Klass* substitute_oop_array_klass(Klass* klass) { 44 return klass == Universe::objectArrayKlassObj() ? Universe::longArrayKlassObj() : klass; 45 } 46 47 ZObjArrayAllocator::ZObjArrayAllocator(Klass* klass, size_t word_size, int length, Thread* thread) : 48 ObjArrayAllocator(substitute_oop_array_klass(klass), word_size, length, false /* do_zero */, thread), 49 _final_klass(klass) {} 50 51 oop ZObjArrayAllocator::finish(HeapWord* mem) const { 52 HandleMark hm; 53 Handle array(_thread, ObjArrayAllocator::finish(mem)); 54 55 // Clear array 56 const size_t segment_max = ZUtils::bytes_to_words(64 * K); 57 const size_t skip = arrayOopDesc::header_size(ArrayKlass::cast(_klass)->element_type()); 58 size_t remaining = _word_size - skip; 59 60 while (remaining > 0) { 61 // Clear segment 62 const size_t segment = MIN2(remaining, segment_max); 63 Copy::zero_to_words((HeapWord*)array() + (_word_size - remaining), segment); 64 remaining -= segment; 65 66 // Safepoint 67 ThreadBlockInVM tbivm((JavaThread*)_thread); 68 } 69 70 if (_klass != _final_klass) { 71 // Set final klass 72 oopDesc::release_set_klass((HeapWord*)array(), _final_klass); 73 } 74 75 return array(); 76 }