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

 /*

  * Copyright (c) 2011, 2014, 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* volatile _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.

   uint _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 {

     HeapRegion * hr = _alloc_region;

     // Make sure that the dummy region does not escape this class.

     return (hr == _dummy_region) ? NULL : hr;

   }

   uint 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("%s", "") {

     alloc_region->fill_in_ext_msg(this, message);

   }

 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP