view src/share/vm/gc_implementation/g1/g1AllocRegion.hpp @ 2593:f44782f04dd4

7039627: G1: avoid BOT updates for survivor allocations and dirty survivor regions incrementally Summary: Refactor the allocation code during GC to use the G1AllocRegion abstraction. Use separate subclasses of G1AllocRegion for survivor and old regions. Avoid BOT updates and dirty survivor cards incrementally for the former. Reviewed-by: brutisso, johnc, ysr
author tonyp
date Fri, 12 Aug 2011 11:31:06 -0400
parents abdfc822206f
children 720b6a76dd9d
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/*
 * Copyright (c) 2011, 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP
#define SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP

#include "gc_implementation/g1/heapRegion.hpp"

class G1CollectedHeap;

// 0 -> no tracing, 1 -> basic tracing, 2 -> basic + allocation tracing
#define G1_ALLOC_REGION_TRACING 0

class ar_ext_msg;

// A class that holds a region that is active in satisfying allocation
// requests, potentially issued in parallel. When the active region is
// full it will be retired and replaced with a new one. The
// implementation assumes that fast-path allocations will be lock-free
// and a lock will need to be taken when the active region needs to be
// replaced.

class G1AllocRegion VALUE_OBJ_CLASS_SPEC {
  friend class ar_ext_msg;

private:
  // The active allocating region we are currently allocating out
  // of. The invariant is that if this object is initialized (i.e.,
  // init() has been called and release() has not) then _alloc_region
  // is either an active allocating region or the dummy region (i.e.,
  // it can never be NULL) and this object can be used to satisfy
  // allocation requests. If this object is not initialized
  // (i.e. init() has not been called or release() has been called)
  // then _alloc_region is NULL and this object should not be used to
  // satisfy allocation requests (it was done this way to force the
  // correct use of init() and release()).
  HeapRegion* _alloc_region;

  // It keeps track of the distinct number of regions that are used
  // for allocation in the active interval of this object, i.e.,
  // between a call to init() and a call to release(). The count
  // mostly includes regions that are freshly allocated, as well as
  // the region that is re-used using the set() method. This count can
  // be used in any heuristics that might want to bound how many
  // distinct regions this object can used during an active interval.
  size_t _count;

  // When we set up a new active region we save its used bytes in this
  // field so that, when we retire it, we can calculate how much space
  // we allocated in it.
  size_t _used_bytes_before;

  // When true, indicates that allocate calls should do BOT updates.
  const bool _bot_updates;

  // Useful for debugging and tracing.
  const char* _name;

  // A dummy region (i.e., it's been allocated specially for this
  // purpose and it is not part of the heap) that is full (i.e., top()
  // == end()). When we don't have a valid active region we make
  // _alloc_region point to this. This allows us to skip checking
  // whether the _alloc_region is NULL or not.
  static HeapRegion* _dummy_region;

  // Some of the methods below take a bot_updates parameter. Its value
  // should be the same as the _bot_updates field. The idea is that
  // the parameter will be a constant for a particular alloc region
  // and, given that these methods will be hopefully inlined, the
  // compiler should compile out the test.

  // Perform a non-MT-safe allocation out of the given region.
  static inline HeapWord* allocate(HeapRegion* alloc_region,
                                   size_t word_size,
                                   bool bot_updates);

  // Perform a MT-safe allocation out of the given region.
  static inline HeapWord* par_allocate(HeapRegion* alloc_region,
                                       size_t word_size,
                                       bool bot_updates);

  // Ensure that the region passed as a parameter has been filled up
  // so that noone else can allocate out of it any more.
  static void fill_up_remaining_space(HeapRegion* alloc_region,
                                      bool bot_updates);

  // Retire the active allocating region. If fill_up is true then make
  // sure that the region is full before we retire it so that noone
  // else can allocate out of it.
  void retire(bool fill_up);

  // Allocate a new active region and use it to perform a word_size
  // allocation. The force parameter will be passed on to
  // G1CollectedHeap::allocate_new_alloc_region() and tells it to try
  // to allocate a new region even if the max has been reached.
  HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);

  void fill_in_ext_msg(ar_ext_msg* msg, const char* message);

protected:
  // For convenience as subclasses use it.
  static G1CollectedHeap* _g1h;

  virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;
  virtual void retire_region(HeapRegion* alloc_region,
                             size_t allocated_bytes) = 0;

  G1AllocRegion(const char* name, bool bot_updates);

public:
  static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);

  HeapRegion* get() const {
    // Make sure that the dummy region does not escape this class.
    return (_alloc_region == _dummy_region) ? NULL : _alloc_region;
  }

  size_t count() { return _count; }

  // The following two are the building blocks for the allocation method.

  // First-level allocation: Should be called without holding a
  // lock. It will try to allocate lock-free out of the active region,
  // or return NULL if it was unable to.
  inline HeapWord* attempt_allocation(size_t word_size, bool bot_updates);

  // Second-level allocation: Should be called while holding a
  // lock. It will try to first allocate lock-free out of the active
  // region or, if it's unable to, it will try to replace the active
  // alloc region with a new one. We require that the caller takes the
  // appropriate lock before calling this so that it is easier to make
  // it conform to its locking protocol.
  inline HeapWord* attempt_allocation_locked(size_t word_size,
                                             bool bot_updates);

  // Should be called to allocate a new region even if the max of this
  // type of regions has been reached. Should only be called if other
  // allocation attempts have failed and we are not holding a valid
  // active region.
  inline HeapWord* attempt_allocation_force(size_t word_size,
                                            bool bot_updates);

  // Should be called before we start using this object.
  void init();

  // This can be used to set the active region to a specific
  // region. (Use Example: we try to retain the last old GC alloc
  // region that we've used during a GC and we can use set() to
  // re-instate it at the beginning of the next GC.)
  void set(HeapRegion* alloc_region);

  // Should be called when we want to release the active region which
  // is returned after it's been retired.
  HeapRegion* release();

#if G1_ALLOC_REGION_TRACING
  void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL);
#else // G1_ALLOC_REGION_TRACING
  void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL) { }
#endif // G1_ALLOC_REGION_TRACING
};

class ar_ext_msg : public err_msg {
public:
  ar_ext_msg(G1AllocRegion* alloc_region, const char *message) : err_msg("") {
    alloc_region->fill_in_ext_msg(this, message);
  }
};

#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP