src/hotspot/share/gc/shenandoah/shenandoahTraversalGC.inline.hpp
author shade
Mon, 21 Oct 2019 22:44:48 +0200
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8232730: Shenandoah: Traversal should not CAS the roots Reviewed-by: zgu, rkennke
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/*
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 * Copyright (c) 2018, Red Hat, Inc. All rights reserved.
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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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 */
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#ifndef SHARE_GC_SHENANDOAH_SHENANDOAHTRAVERSALGC_INLINE_HPP
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#define SHARE_GC_SHENANDOAH_SHENANDOAHTRAVERSALGC_INLINE_HPP
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#include "gc/shenandoah/shenandoahAsserts.hpp"
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#include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
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#include "gc/shenandoah/shenandoahHeap.inline.hpp"
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#include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
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#include "gc/shenandoah/shenandoahStringDedup.hpp"
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#include "gc/shenandoah/shenandoahTraversalGC.hpp"
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#include "gc/shenandoah/shenandoahTaskqueue.hpp"
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#include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
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#include "oops/compressedOops.inline.hpp"
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#include "oops/oop.inline.hpp"
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template <class T, bool STRING_DEDUP, bool DEGEN, bool ATOMIC_UPDATE>
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void ShenandoahTraversalGC::process_oop(T* p, Thread* thread, ShenandoahObjToScanQueue* queue, ShenandoahMarkingContext* const mark_context) {
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  T o = RawAccess<>::oop_load(p);
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  if (!CompressedOops::is_null(o)) {
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    oop obj = CompressedOops::decode_not_null(o);
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    if (DEGEN) {
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      assert(!ATOMIC_UPDATE, "Degen path assumes non-atomic updates");
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      oop forw = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
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      if (obj != forw) {
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        // Update reference.
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        RawAccess<IS_NOT_NULL>::oop_store(p, forw);
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      }
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      obj = forw;
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    } else if (_heap->in_collection_set(obj)) {
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      oop forw = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
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      if (obj == forw) {
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        forw = _heap->evacuate_object(obj, thread);
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      }
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      shenandoah_assert_forwarded_except(p, obj, _heap->cancelled_gc());
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      // Update reference.
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      if (ATOMIC_UPDATE) {
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        ShenandoahHeap::cas_oop(forw, p, obj);
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      } else {
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        RawAccess<IS_NOT_NULL>::oop_store(p, forw);
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      }
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      obj = forw;
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    }
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    shenandoah_assert_not_forwarded(p, obj);
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    shenandoah_assert_not_in_cset_except(p, obj, _heap->cancelled_gc());
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    if (mark_context->mark(obj)) {
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      bool succeeded = queue->push(ShenandoahMarkTask(obj));
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      assert(succeeded, "must succeed to push to task queue");
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      if (STRING_DEDUP && ShenandoahStringDedup::is_candidate(obj) && !_heap->cancelled_gc()) {
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        assert(ShenandoahStringDedup::is_enabled(), "Must be enabled");
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        // Only dealing with to-space string, so that we can avoid evac-oom protocol, which is costly here.
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        shenandoah_assert_not_in_cset(p, obj);
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        ShenandoahStringDedup::enqueue_candidate(obj);
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      }
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    }
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  }
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}
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#endif // SHARE_GC_SHENANDOAH_SHENANDOAHTRAVERSALGC_INLINE_HPP