src/hotspot/share/gc/z/zForwarding.cpp
author pliden
Mon, 18 Mar 2019 11:50:39 +0100
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child 54172 f92f1f1045ad
permissions -rw-r--r--
8220588: ZGC: Convert ZRelocationSet to hold ZForwardings instead of ZPages Reviewed-by: stefank, eosterlund
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/*
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 * Copyright (c) 2015, 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/zForwarding.inline.hpp"
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#include "gc/z/zPage.inline.hpp"
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#include "gc/z/zUtils.inline.hpp"
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#include "memory/allocation.hpp"
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#include "utilities/debug.hpp"
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ZForwarding::ZForwarding(ZPage* page, uint32_t nentries) :
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    _virtual(page->virtual_memory()),
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    _object_alignment_shift(page->object_alignment_shift()),
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    _nentries(nentries),
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    _page(page),
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    _refcount(1),
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    _pinned(false) {}
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ZForwarding* ZForwarding::create(ZPage* page) {
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  assert(page->live_objects() > 0, "Invalid value");
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  // Allocate table for linear probing. The size of the table must be
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  // a power of two to allow for quick and inexpensive indexing/masking.
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  // The table is sized to have a load factor of 50%, i.e. sized to have
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  // double the number of entries actually inserted.
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  const uint32_t nentries = ZUtils::round_up_power_of_2(page->live_objects() * 2);
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  const size_t size = sizeof(ZForwarding) + (sizeof(ZForwardingEntry) * nentries);
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  uint8_t* const addr = NEW_C_HEAP_ARRAY(uint8_t, size, mtGC);
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  ZForwardingEntry* const entries = ::new (addr + sizeof(ZForwarding)) ZForwardingEntry[nentries];
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  ZForwarding* const forwarding = ::new (addr) ZForwarding(page, nentries);
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  return forwarding;
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}
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void ZForwarding::destroy(ZForwarding* forwarding) {
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  FREE_C_HEAP_ARRAY(uint8_t, forwarding);
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}
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void ZForwarding::verify() const {
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  guarantee(_refcount > 0, "Invalid refcount");
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  guarantee(_page != NULL, "Invalid page");
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  uint32_t live_objects = 0;
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  for (ZForwardingCursor i = 0; i < _nentries; i++) {
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    const ZForwardingEntry entry = at(&i);
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    if (entry.is_empty()) {
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      // Skip empty entries
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      continue;
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    }
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    // Check from index
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    guarantee(entry.from_index() < _page->object_max_count(), "Invalid from index");
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    // Check for duplicates
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    for (ZForwardingCursor j = i + 1; j < _nentries; j++) {
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      const ZForwardingEntry other = at(&j);
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      guarantee(entry.from_index() != other.from_index(), "Duplicate from");
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      guarantee(entry.to_offset() != other.to_offset(), "Duplicate to");
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    }
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    live_objects++;
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  }
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  // Check number of non-empty entries
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  guarantee(live_objects == _page->live_objects(), "Invalid number of entries");
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}