hotspot/src/share/vm/memory/defNewGeneration.inline.hpp
author ysr
Thu, 03 Dec 2009 15:01:57 -0800
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permissions -rw-r--r--
6906727: UseCompressedOops: some card-marking fixes related to object arrays Summary: Introduced a new write_ref_array(HeapWords* start, size_t count) method that does the requisite MemRegion range calculation so (some of the) clients of the erstwhile write_ref_array(MemRegion mr) do not need to worry. This removed all external uses of array_size(), which was also simplified and made private. Asserts were added to catch other possible issues. Further, less essential, fixes stemming from this investigation are deferred to CR 6904516 (to follow shortly in hs17). Reviewed-by: kvn, coleenp, jmasa
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/*
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 * Copyright 2001-2008 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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 * CA 95054 USA or visit www.sun.com if you need additional information or
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 * have any questions.
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 *
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 */
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// Methods of protected closure types
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template <class T>
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inline void DefNewGeneration::KeepAliveClosure::do_oop_work(T* p) {
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#ifdef ASSERT
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  {
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    // We never expect to see a null reference being processed
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    // as a weak reference.
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    assert (!oopDesc::is_null(*p), "expected non-null ref");
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    oop obj = oopDesc::load_decode_heap_oop_not_null(p);
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    assert (obj->is_oop(), "expected an oop while scanning weak refs");
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  }
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#endif // ASSERT
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  _cl->do_oop_nv(p);
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  // Card marking is trickier for weak refs.
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  // This oop is a 'next' field which was filled in while we
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  // were discovering weak references. While we might not need
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  // to take a special action to keep this reference alive, we
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  // will need to dirty a card as the field was modified.
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  //
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  // Alternatively, we could create a method which iterates through
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  // each generation, allowing them in turn to examine the modified
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  // field.
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  //
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  // We could check that p is also in an older generation, but
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  // dirty cards in the youngest gen are never scanned, so the
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  // extra check probably isn't worthwhile.
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  if (Universe::heap()->is_in_reserved(p)) {
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    oop obj = oopDesc::load_decode_heap_oop_not_null(p);
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    _rs->inline_write_ref_field_gc(p, obj);
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  }
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}
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template <class T>
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inline void DefNewGeneration::FastKeepAliveClosure::do_oop_work(T* p) {
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#ifdef ASSERT
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  {
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    // We never expect to see a null reference being processed
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    // as a weak reference.
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    assert (!oopDesc::is_null(*p), "expected non-null ref");
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    oop obj = oopDesc::load_decode_heap_oop_not_null(p);
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    assert (obj->is_oop(), "expected an oop while scanning weak refs");
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  }
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#endif // ASSERT
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  _cl->do_oop_nv(p);
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  // Optimized for Defnew generation if it's the youngest generation:
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  // we set a younger_gen card if we have an older->youngest
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  // generation pointer.
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  oop obj = oopDesc::load_decode_heap_oop_not_null(p);
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  if (((HeapWord*)obj < _boundary) && Universe::heap()->is_in_reserved(p)) {
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    _rs->inline_write_ref_field_gc(p, obj);
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  }
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}