view src/share/vm/runtime/aprofiler.hpp @ 1716:be3f9c242c9d

6948538: CMS: BOT walkers can fall into object allocation and initialization cracks Summary: GC workers now recognize an intermediate transient state of blocks which are allocated but have not yet completed initialization. blk_start() calls do not attempt to determine the size of a block in the transient state, rather waiting for the block to become initialized so that it is safe to query its size. Audited and ensured the order of initialization of object fields (klass, free bit and size) to respect block state transition protocol. Also included some new assertion checking code enabled in debug mode. Reviewed-by: chrisphi, johnc, poonam
author ysr
date Mon, 16 Aug 2010 15:58:42 -0700
parents c18cbe5936b8
children f95d63e2154a
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/*
 * Copyright (c) 1997, 2003, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

// A simple allocation profiler for Java. The profiler collects and prints
// the number and total size of instances allocated per class, including
// array classes.
//
// The profiler is currently global for all threads. It can be changed to a
// per threads profiler by keeping a more elaborate data structure and calling
// iterate_since_last_scavenge at thread switches.


class AllocationProfiler: AllStatic {
  friend class GenCollectedHeap;
  friend class G1CollectedHeap;
  friend class MarkSweep;
 private:
  static bool _active;                          // tells whether profiler is active
  static GrowableArray<klassOop>* _print_array; // temporary array for printing

  // Utility printing functions
  static void add_class_to_array(klassOop k);
  static void add_classes_to_array(klassOop k);
  static int  compare_classes(klassOop* k1, klassOop* k2);
  static int  average(size_t alloc_size, int alloc_count);
  static void sort_and_print_array(size_t cutoff);

  // Call for collecting allocation information. Called at scavenge, mark-sweep and disengage.
  static void iterate_since_last_gc();

 public:
  // Start profiler
  static void engage();
  // Stop profiler
  static void disengage();
  // Tells whether profiler is active
  static bool is_active()                   { return _active; }
  // Print profile
  static void print(size_t cutoff);   // Cutoff in total allocation size (in words)
};