jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/g1/g1CodeCacheRemSet.hpp@e7d0505c8a30

8059758: Footprint regressions with JDK-8038423
Summary: Changes in JDK-8038423 always initialize (zero out) virtual memory used for auxiliary data structures. This causes a footprint regression for G1 in startup benchmarks. This is because they do not touch that memory at all, so the operating system does not actually commit these pages. The fix is to, if the initialization value of the data structures matches the default value of just committed memory (=0), do not do anything.
Reviewed-by: jwilhelm, brutisso

     1 /*

     2  * Copyright (c) 2014, 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  */

    25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1CODECACHEREMSET_HPP

    26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1CODECACHEREMSET_HPP

    28 #include "memory/allocation.hpp"

    30 class CodeBlobClosure;

    31 class CodeRootSetTable;

    32 class HeapRegion;

    33 class nmethod;

    35 // Implements storage for a set of code roots.

    36 // All methods that modify the set are not thread-safe except if otherwise noted.

    37 class G1CodeRootSet VALUE_OBJ_CLASS_SPEC {

    38   friend class G1CodeRootSetTest;

    39  private:

    41   const static size_t SmallSize = 32;

    42   const static size_t Threshold = 24;

    43   const static size_t LargeSize = 512;

    45   CodeRootSetTable* _table;

    46   CodeRootSetTable* load_acquire_table();

    48   size_t _length;

    50   void move_to_large();

    51   void allocate_small_table();

    53  public:

    54   G1CodeRootSet() : _table(NULL), _length(0) {}

    55   ~G1CodeRootSet();

    57   static void purge();

    59   static size_t static_mem_size();

    61   void add(nmethod* method);

    63   bool remove(nmethod* method);

    65   // Safe to call without synchronization, but may return false negatives.

    66   bool contains(nmethod* method);

    68   void clear();

    70   void nmethods_do(CodeBlobClosure* blk) const;

    72   // Remove all nmethods which no longer contain pointers into our "owner" region

    73   void clean(HeapRegion* owner);

    75   bool is_empty() {

    76     bool empty = length() == 0;

    77     assert(empty == (_table == NULL), "is empty only if table is deallocated");

    78     return empty;

    79   }

    81   // Length in elements

    82   size_t length() const { return _length; }

    84   // Memory size in bytes taken by this set.

    85   size_t mem_size();

    87 };

    89 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1CODECACHEREMSET_HPP

Mercurial > jdk8-mips64-public > hotspot / file revision

src/share/vm/gc_implementation/g1/g1CodeCacheRemSet.hpp@e7d0505c8a30

src/share/vm/gc_implementation/g1/g1CodeCacheRemSet.hpp