jdk8-mips64-public/hotspot: src/share/vm/memory/sharedHeap.hpp@f90c822e73f8 (annotated)

src/share/vm/memory/sharedHeap.hpp@f90c822e73f8 (annotated)

src/share/vm/memory/sharedHeap.hpp

Wed, 27 Apr 2016 01:25:04 +0800

author: aoqi
date: Wed, 27 Apr 2016 01:25:04 +0800
changeset 0: f90c822e73f8
child 6876: 710a3c8b516e
permissions: -rw-r--r--

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http://hg.openjdk.java.net/jdk8u/jdk8u/hotspot/
changeset: 6782:28b50d07f6f8
tag: jdk8u25-b17

 /*
  * Copyright (c) 2000, 2013, 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_MEMORY_SHAREDHEAP_HPP
 #define SHARE_VM_MEMORY_SHAREDHEAP_HPP
 #include "gc_interface/collectedHeap.hpp"
 #include "memory/generation.hpp"
 // A "SharedHeap" is an implementation of a java heap for HotSpot.  This
 // is an abstract class: there may be many different kinds of heaps.  This
 // class defines the functions that a heap must implement, and contains
 // infrastructure common to all heaps.
 class Generation;
 class BarrierSet;
 class GenRemSet;
 class Space;
 class SpaceClosure;
 class OopClosure;
 class OopsInGenClosure;
 class ObjectClosure;
 class SubTasksDone;
 class WorkGang;
 class FlexibleWorkGang;
 class CollectorPolicy;
 class KlassClosure;
 // Note on use of FlexibleWorkGang's for GC.
 // There are three places where task completion is determined.
 // In
 //    1) ParallelTaskTerminator::offer_termination() where _n_threads
 //    must be set to the correct value so that count of workers that
 //    have offered termination will exactly match the number
 //    working on the task.  Tasks such as those derived from GCTask
 //    use ParallelTaskTerminator's.  Tasks that want load balancing
 //    by work stealing use this method to gauge completion.
 //    2) SubTasksDone has a variable _n_threads that is used in
 //    all_tasks_completed() to determine completion.  all_tasks_complete()
 //    counts the number of tasks that have been done and then reset
 //    the SubTasksDone so that it can be used again.  When the number of
 //    tasks is set to the number of GC workers, then _n_threads must
 //    be set to the number of active GC workers. G1CollectedHeap,
 //    HRInto_G1RemSet, GenCollectedHeap and SharedHeap have SubTasksDone.
 //    This seems too many.
 //    3) SequentialSubTasksDone has an _n_threads that is used in
 //    a way similar to SubTasksDone and has the same dependency on the
 //    number of active GC workers.  CompactibleFreeListSpace and Space
 //    have SequentialSubTasksDone's.
 // Example of using SubTasksDone and SequentialSubTasksDone
 // G1CollectedHeap::g1_process_strong_roots() calls
 //  process_strong_roots(false, // no scoping; this is parallel code
 //                       is_scavenging, so,
 //                       &buf_scan_non_heap_roots,
 //                       &eager_scan_code_roots);
 //  which delegates to SharedHeap::process_strong_roots() and uses
 //  SubTasksDone* _process_strong_tasks to claim tasks.
 //  process_strong_roots() calls
 //      rem_set()->younger_refs_iterate()
 //  to scan the card table and which eventually calls down into
 //  CardTableModRefBS::par_non_clean_card_iterate_work().  This method
 //  uses SequentialSubTasksDone* _pst to claim tasks.
 //  Both SubTasksDone and SequentialSubTasksDone call their method
 //  all_tasks_completed() to count the number of GC workers that have
 //  finished their work.  That logic is "when all the workers are
 //  finished the tasks are finished".
 //
 //  The pattern that appears  in the code is to set _n_threads
 //  to a value > 1 before a task that you would like executed in parallel
 //  and then to set it to 0 after that task has completed.  A value of
 //  0 is a "special" value in set_n_threads() which translates to
 //  setting _n_threads to 1.
 //
 //  Some code uses _n_terminiation to decide if work should be done in
 //  parallel.  The notorious possibly_parallel_oops_do() in threads.cpp
 //  is an example of such code.  Look for variable "is_par" for other
 //  examples.
 //
 //  The active_workers is not reset to 0 after a parallel phase.  It's
 //  value may be used in later phases and in one instance at least
 //  (the parallel remark) it has to be used (the parallel remark depends
 //  on the partitioning done in the previous parallel scavenge).
 class SharedHeap : public CollectedHeap {
   friend class VMStructs;
   friend class VM_GC_Operation;
   friend class VM_CGC_Operation;
 private:
   // For claiming strong_roots tasks.
   SubTasksDone* _process_strong_tasks;
 protected:
   // There should be only a single instance of "SharedHeap" in a program.
   // This is enforced with the protected constructor below, which will also
   // set the static pointer "_sh" to that instance.
   static SharedHeap* _sh;
   // and the Gen Remembered Set, at least one good enough to scan the perm
   // gen.
   GenRemSet* _rem_set;
   // A gc policy, controls global gc resource issues
   CollectorPolicy *_collector_policy;
   // See the discussion below, in the specification of the reader function
   // for this variable.
   int _strong_roots_parity;
   // If we're doing parallel GC, use this gang of threads.
   FlexibleWorkGang* _workers;
   // Full initialization is done in a concrete subtype's "initialize"
   // function.
   SharedHeap(CollectorPolicy* policy_);
   // Returns true if the calling thread holds the heap lock,
   // or the calling thread is a par gc thread and the heap_lock is held
   // by the vm thread doing a gc operation.
   bool heap_lock_held_for_gc();
   // True if the heap_lock is held by the a non-gc thread invoking a gc
   // operation.
   bool _thread_holds_heap_lock_for_gc;
 public:
   static SharedHeap* heap() { return _sh; }
   void set_barrier_set(BarrierSet* bs);
   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
   // Does operations required after initialization has been done.
   virtual void post_initialize();
   // Initialization of ("weak") reference processing support
   virtual void ref_processing_init();
   // This function returns the "GenRemSet" object that allows us to scan
   // generations in a fully generational heap.
   GenRemSet* rem_set() { return _rem_set; }
   // Iteration functions.
   void oop_iterate(ExtendedOopClosure* cl) = 0;
   // Same as above, restricted to a memory region.
   virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl) = 0;
   // Iterate over all spaces in use in the heap, in an undefined order.
   virtual void space_iterate(SpaceClosure* cl) = 0;
   // A SharedHeap will contain some number of spaces.  This finds the
   // space whose reserved area contains the given address, or else returns
   // NULL.
   virtual Space* space_containing(const void* addr) const = 0;
   bool no_gc_in_progress() { return !is_gc_active(); }
   // Some collectors will perform "process_strong_roots" in parallel.
   // Such a call will involve claiming some fine-grained tasks, such as
   // scanning of threads.  To make this process simpler, we provide the
   // "strong_roots_parity()" method.  Collectors that start parallel tasks
   // whose threads invoke "process_strong_roots" must
   // call "change_strong_roots_parity" in sequential code starting such a
   // task.  (This also means that a parallel thread may only call
   // process_strong_roots once.)
   //
   // For calls to process_strong_roots by sequential code, the parity is
   // updated automatically.
   //
   // The idea is that objects representing fine-grained tasks, such as
   // threads, will contain a "parity" field.  A task will is claimed in the
   // current "process_strong_roots" call only if its parity field is the
   // same as the "strong_roots_parity"; task claiming is accomplished by
   // updating the parity field to the strong_roots_parity with a CAS.
   //
   // If the client meats this spec, then strong_roots_parity() will have
   // the following properties:
   //   a) to return a different value than was returned before the last
   //      call to change_strong_roots_parity, and
   //   c) to never return a distinguished value (zero) with which such
   //      task-claiming variables may be initialized, to indicate "never
   //      claimed".
  private:
   void change_strong_roots_parity();
  public:
   int strong_roots_parity() { return _strong_roots_parity; }
   // Call these in sequential code around process_strong_roots.
   // strong_roots_prologue calls change_strong_roots_parity, if
   // parallel tasks are enabled.
   class StrongRootsScope : public MarkingCodeBlobClosure::MarkScope {
   public:
     StrongRootsScope(SharedHeap* outer, bool activate = true);
     ~StrongRootsScope();
   };
   friend class StrongRootsScope;
   enum ScanningOption {
     SO_None                = 0x0,
     SO_AllClasses          = 0x1,
     SO_SystemClasses       = 0x2,
     SO_Strings             = 0x4,
     SO_CodeCache           = 0x8
   };
   FlexibleWorkGang* workers() const { return _workers; }
   // Invoke the "do_oop" method the closure "roots" on all root locations.
   // The "so" argument determines which roots the closure is applied to:
   // "SO_None" does none;
   // "SO_AllClasses" applies the closure to all entries in the SystemDictionary;
   // "SO_SystemClasses" to all the "system" classes and loaders;
   // "SO_Strings" applies the closure to all entries in StringTable;
   // "SO_CodeCache" applies the closure to all elements of the CodeCache.
   void process_strong_roots(bool activate_scope,
                             bool is_scavenging,
                             ScanningOption so,
                             OopClosure* roots,
                             CodeBlobClosure* code_roots,
                             KlassClosure* klass_closure);
   // Apply "blk" to all the weak roots of the system.  These include
   // JNI weak roots, the code cache, system dictionary, symbol table,
   // string table.
   void process_weak_roots(OopClosure* root_closure,
                           CodeBlobClosure* code_roots);
   // The functions below are helper functions that a subclass of
   // "SharedHeap" can use in the implementation of its virtual
   // functions.
 public:
   // Do anything common to GC's.
   virtual void gc_prologue(bool full) = 0;
   virtual void gc_epilogue(bool full) = 0;
   // Sets the number of parallel threads that will be doing tasks
   // (such as process strong roots) subsequently.
   virtual void set_par_threads(uint t);
   int n_termination();
   void set_n_termination(int t);
   //
   // New methods from CollectedHeap
   //
   // Some utilities.
   void print_size_transition(outputStream* out,
                              size_t bytes_before,
                              size_t bytes_after,
                              size_t capacity);
 };
 #endif // SHARE_VM_MEMORY_SHAREDHEAP_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/memory/sharedHeap.hpp@f90c822e73f8 (annotated)

src/share/vm/memory/sharedHeap.hpp