94 lines
3.7 KiB
C++
94 lines
3.7 KiB
C++
/*
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* Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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#include "precompiled.hpp"
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#include "gc/z/zThreadLocalData.hpp"
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#include "gc/z/zObjArrayAllocator.hpp"
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#include "gc/z/zUtils.inline.hpp"
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#include "memory/universe.hpp"
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#include "oops/arrayKlass.hpp"
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#include "runtime/interfaceSupport.inline.hpp"
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#include "runtime/handles.hpp"
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#include "runtime/os.hpp"
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#include "utilities/debug.hpp"
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#include "utilities/globalDefinitions.hpp"
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// To avoid delaying safepoints, clearing of arrays is split up in segments
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// with safepoint polling inbetween. However, we can't have a not-yet-cleared
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// array of oops on the heap when we safepoint since the GC will then stumble
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// across uninitialized oops. To avoid this we let an array of oops be an
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// array of a primitive type of the same size until the clearing has completed.
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// A max segment size of 64K was chosen because benchmarking suggests that is
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// offers a good trade-off between allocation time and time-to-safepoint.
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static Klass* substitute_object_array_klass(Klass* klass) {
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if (!klass->is_objArray_klass()) {
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return klass;
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}
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Klass* const substitute_klass = Universe::longArrayKlassObj();
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const BasicType type = ArrayKlass::cast(klass)->element_type();
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const BasicType substitute_type = ArrayKlass::cast(substitute_klass)->element_type();
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assert(type2aelembytes(type) == type2aelembytes(substitute_type), "Element size mismatch");
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return substitute_klass;
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}
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ZObjArrayAllocator::ZObjArrayAllocator(Klass* klass, size_t word_size, int length, Thread* thread) :
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ObjArrayAllocator(substitute_object_array_klass(klass), word_size, length, false /* do_zero */, thread),
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_final_klass(klass) {}
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oop ZObjArrayAllocator::finish(HeapWord* mem) const {
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// Set mark word and initial klass pointer
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ObjArrayAllocator::finish(mem);
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// Keep the array alive across safepoints, but make it invisible
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// to the heap itarator until the final klass pointer has been set
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ZThreadLocalData::set_invisible_root(_thread, (oop*)&mem);
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const size_t segment_max = ZUtils::bytes_to_words(64 * K);
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const size_t skip = arrayOopDesc::header_size(ArrayKlass::cast(_klass)->element_type());
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size_t remaining = _word_size - skip;
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while (remaining > 0) {
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// Clear segment
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const size_t segment = MIN2(remaining, segment_max);
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Copy::zero_to_words(mem + (_word_size - remaining), segment);
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remaining -= segment;
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if (remaining > 0) {
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// Safepoint
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ThreadBlockInVM tbivm((JavaThread*)_thread);
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}
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}
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if (_klass != _final_klass) {
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// Set final klass pointer
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oopDesc::release_set_klass(mem, _final_klass);
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}
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// Make the array visible to the heap iterator
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ZThreadLocalData::clear_invisible_root(_thread);
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return oop(mem);
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}
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