duke@435: /*
coleenp@4037:  * Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
trims@1907:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907:  * or visit www.oracle.com if you need additional information or have any
trims@1907:  * questions.
duke@435:  *
duke@435:  */
duke@435: 
stefank@2314: #ifndef SHARE_VM_MEMORY_SHAREDHEAP_HPP
stefank@2314: #define SHARE_VM_MEMORY_SHAREDHEAP_HPP
stefank@2314: 
stefank@2314: #include "gc_interface/collectedHeap.hpp"
stefank@2314: #include "memory/generation.hpp"
stefank@2314: 
duke@435: // A "SharedHeap" is an implementation of a java heap for HotSpot.  This
duke@435: // is an abstract class: there may be many different kinds of heaps.  This
duke@435: // class defines the functions that a heap must implement, and contains
duke@435: // infrastructure common to all heaps.
duke@435: 
duke@435: class Generation;
duke@435: class BarrierSet;
duke@435: class GenRemSet;
duke@435: class Space;
duke@435: class SpaceClosure;
duke@435: class OopClosure;
duke@435: class OopsInGenClosure;
duke@435: class ObjectClosure;
duke@435: class SubTasksDone;
duke@435: class WorkGang;
jmasa@2188: class FlexibleWorkGang;
duke@435: class CollectorPolicy;
coleenp@4037: class KlassClosure;
duke@435: 
jmasa@3294: // Note on use of FlexibleWorkGang's for GC.
jmasa@3294: // There are three places where task completion is determined.
jmasa@3294: // In
jmasa@3294: //    1) ParallelTaskTerminator::offer_termination() where _n_threads
jmasa@3294: //    must be set to the correct value so that count of workers that
jmasa@3294: //    have offered termination will exactly match the number
jmasa@3294: //    working on the task.  Tasks such as those derived from GCTask
jmasa@3294: //    use ParallelTaskTerminator's.  Tasks that want load balancing
jmasa@3294: //    by work stealing use this method to gauge completion.
jmasa@3294: //    2) SubTasksDone has a variable _n_threads that is used in
jmasa@3294: //    all_tasks_completed() to determine completion.  all_tasks_complete()
jmasa@3294: //    counts the number of tasks that have been done and then reset
jmasa@3294: //    the SubTasksDone so that it can be used again.  When the number of
jmasa@3294: //    tasks is set to the number of GC workers, then _n_threads must
jmasa@3294: //    be set to the number of active GC workers. G1CollectedHeap,
jmasa@3294: //    HRInto_G1RemSet, GenCollectedHeap and SharedHeap have SubTasksDone.
jmasa@3294: //    This seems too many.
jmasa@3294: //    3) SequentialSubTasksDone has an _n_threads that is used in
jmasa@3294: //    a way similar to SubTasksDone and has the same dependency on the
jmasa@3294: //    number of active GC workers.  CompactibleFreeListSpace and Space
jmasa@3294: //    have SequentialSubTasksDone's.
jmasa@3294: // Example of using SubTasksDone and SequentialSubTasksDone
jmasa@3294: // G1CollectedHeap::g1_process_strong_roots() calls
jmasa@3294: //  process_strong_roots(false, // no scoping; this is parallel code
coleenp@4037: //                       is_scavenging, so,
jmasa@3294: //                       &buf_scan_non_heap_roots,
coleenp@4037: //                       &eager_scan_code_roots);
jmasa@3294: //  which delegates to SharedHeap::process_strong_roots() and uses
jmasa@3294: //  SubTasksDone* _process_strong_tasks to claim tasks.
jmasa@3294: //  process_strong_roots() calls
coleenp@4037: //      rem_set()->younger_refs_iterate()
jmasa@3294: //  to scan the card table and which eventually calls down into
jmasa@3294: //  CardTableModRefBS::par_non_clean_card_iterate_work().  This method
jmasa@3294: //  uses SequentialSubTasksDone* _pst to claim tasks.
jmasa@3294: //  Both SubTasksDone and SequentialSubTasksDone call their method
jmasa@3294: //  all_tasks_completed() to count the number of GC workers that have
jmasa@3294: //  finished their work.  That logic is "when all the workers are
jmasa@3294: //  finished the tasks are finished".
jmasa@3294: //
jmasa@3294: //  The pattern that appears  in the code is to set _n_threads
jmasa@3294: //  to a value > 1 before a task that you would like executed in parallel
jmasa@3294: //  and then to set it to 0 after that task has completed.  A value of
jmasa@3294: //  0 is a "special" value in set_n_threads() which translates to
jmasa@3294: //  setting _n_threads to 1.
jmasa@3294: //
jmasa@3294: //  Some code uses _n_terminiation to decide if work should be done in
jmasa@3294: //  parallel.  The notorious possibly_parallel_oops_do() in threads.cpp
jmasa@3294: //  is an example of such code.  Look for variable "is_par" for other
jmasa@3294: //  examples.
jmasa@3294: //
jmasa@3294: //  The active_workers is not reset to 0 after a parallel phase.  It's
jmasa@3294: //  value may be used in later phases and in one instance at least
jmasa@3294: //  (the parallel remark) it has to be used (the parallel remark depends
jmasa@3294: //  on the partitioning done in the previous parallel scavenge).
jmasa@3294: 
duke@435: class SharedHeap : public CollectedHeap {
duke@435:   friend class VMStructs;
duke@435: 
ysr@777:   friend class VM_GC_Operation;
ysr@777:   friend class VM_CGC_Operation;
ysr@777: 
duke@435: private:
duke@435:   // For claiming strong_roots tasks.
duke@435:   SubTasksDone* _process_strong_tasks;
duke@435: 
duke@435: protected:
duke@435:   // There should be only a single instance of "SharedHeap" in a program.
duke@435:   // This is enforced with the protected constructor below, which will also
duke@435:   // set the static pointer "_sh" to that instance.
duke@435:   static SharedHeap* _sh;
duke@435: 
duke@435:   // and the Gen Remembered Set, at least one good enough to scan the perm
duke@435:   // gen.
duke@435:   GenRemSet* _rem_set;
duke@435: 
duke@435:   // A gc policy, controls global gc resource issues
duke@435:   CollectorPolicy *_collector_policy;
duke@435: 
duke@435:   // See the discussion below, in the specification of the reader function
duke@435:   // for this variable.
duke@435:   int _strong_roots_parity;
duke@435: 
duke@435:   // If we're doing parallel GC, use this gang of threads.
jmasa@2188:   FlexibleWorkGang* _workers;
duke@435: 
duke@435:   // Full initialization is done in a concrete subtype's "initialize"
duke@435:   // function.
duke@435:   SharedHeap(CollectorPolicy* policy_);
duke@435: 
ysr@777:   // Returns true if the calling thread holds the heap lock,
ysr@777:   // or the calling thread is a par gc thread and the heap_lock is held
ysr@777:   // by the vm thread doing a gc operation.
ysr@777:   bool heap_lock_held_for_gc();
ysr@777:   // True if the heap_lock is held by the a non-gc thread invoking a gc
ysr@777:   // operation.
ysr@777:   bool _thread_holds_heap_lock_for_gc;
ysr@777: 
duke@435: public:
duke@435:   static SharedHeap* heap() { return _sh; }
duke@435: 
duke@435:   void set_barrier_set(BarrierSet* bs);
jmasa@3294:   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
duke@435: 
duke@435:   // Does operations required after initialization has been done.
duke@435:   virtual void post_initialize();
duke@435: 
duke@435:   // Initialization of ("weak") reference processing support
duke@435:   virtual void ref_processing_init();
duke@435: 
duke@435:   // This function returns the "GenRemSet" object that allows us to scan
coleenp@4037:   // generations in a fully generational heap.
duke@435:   GenRemSet* rem_set() { return _rem_set; }
duke@435: 
duke@435:   // Iteration functions.
coleenp@4037:   void oop_iterate(ExtendedOopClosure* cl) = 0;
duke@435: 
duke@435:   // Same as above, restricted to a memory region.
coleenp@4037:   virtual void oop_iterate(MemRegion mr, ExtendedOopClosure* cl) = 0;
duke@435: 
duke@435:   // Iterate over all objects allocated since the last collection, calling
duke@435:   // "cl->do_object" on each.  The heap must have been initialized properly
duke@435:   // to support this function, or else this call will fail.
duke@435:   virtual void object_iterate_since_last_GC(ObjectClosure* cl) = 0;
duke@435: 
duke@435:   // Iterate over all spaces in use in the heap, in an undefined order.
duke@435:   virtual void space_iterate(SpaceClosure* cl) = 0;
duke@435: 
duke@435:   // A SharedHeap will contain some number of spaces.  This finds the
duke@435:   // space whose reserved area contains the given address, or else returns
duke@435:   // NULL.
duke@435:   virtual Space* space_containing(const void* addr) const = 0;
duke@435: 
duke@435:   bool no_gc_in_progress() { return !is_gc_active(); }
duke@435: 
duke@435:   // Some collectors will perform "process_strong_roots" in parallel.
duke@435:   // Such a call will involve claiming some fine-grained tasks, such as
duke@435:   // scanning of threads.  To make this process simpler, we provide the
duke@435:   // "strong_roots_parity()" method.  Collectors that start parallel tasks
duke@435:   // whose threads invoke "process_strong_roots" must
duke@435:   // call "change_strong_roots_parity" in sequential code starting such a
duke@435:   // task.  (This also means that a parallel thread may only call
duke@435:   // process_strong_roots once.)
duke@435:   //
duke@435:   // For calls to process_strong_roots by sequential code, the parity is
duke@435:   // updated automatically.
duke@435:   //
duke@435:   // The idea is that objects representing fine-grained tasks, such as
duke@435:   // threads, will contain a "parity" field.  A task will is claimed in the
duke@435:   // current "process_strong_roots" call only if its parity field is the
duke@435:   // same as the "strong_roots_parity"; task claiming is accomplished by
duke@435:   // updating the parity field to the strong_roots_parity with a CAS.
duke@435:   //
duke@435:   // If the client meats this spec, then strong_roots_parity() will have
duke@435:   // the following properties:
duke@435:   //   a) to return a different value than was returned before the last
duke@435:   //      call to change_strong_roots_parity, and
duke@435:   //   c) to never return a distinguished value (zero) with which such
duke@435:   //      task-claiming variables may be initialized, to indicate "never
duke@435:   //      claimed".
jrose@1424:  private:
duke@435:   void change_strong_roots_parity();
jrose@1424:  public:
duke@435:   int strong_roots_parity() { return _strong_roots_parity; }
duke@435: 
jrose@1424:   // Call these in sequential code around process_strong_roots.
jrose@1424:   // strong_roots_prologue calls change_strong_roots_parity, if
jrose@1424:   // parallel tasks are enabled.
jrose@1424:   class StrongRootsScope : public MarkingCodeBlobClosure::MarkScope {
jrose@1424:   public:
jrose@1424:     StrongRootsScope(SharedHeap* outer, bool activate = true);
jrose@1424:     ~StrongRootsScope();
jrose@1424:   };
jrose@1424:   friend class StrongRootsScope;
jrose@1424: 
duke@435:   enum ScanningOption {
duke@435:     SO_None                = 0x0,
duke@435:     SO_AllClasses          = 0x1,
duke@435:     SO_SystemClasses       = 0x2,
ysr@2825:     SO_Strings             = 0x4,
ysr@2825:     SO_CodeCache           = 0x8
duke@435:   };
duke@435: 
jmasa@2188:   FlexibleWorkGang* workers() const { return _workers; }
duke@435: 
duke@435:   // Invoke the "do_oop" method the closure "roots" on all root locations.
coleenp@4037:   // The "so" argument determines which roots the closure is applied to:
duke@435:   // "SO_None" does none;
duke@435:   // "SO_AllClasses" applies the closure to all entries in the SystemDictionary;
duke@435:   // "SO_SystemClasses" to all the "system" classes and loaders;
duke@435:   // "SO_Strings" applies the closure to all entries in StringTable;
duke@435:   // "SO_CodeCache" applies the closure to all elements of the CodeCache.
jrose@1424:   void process_strong_roots(bool activate_scope,
coleenp@4037:                             bool is_scavenging,
duke@435:                             ScanningOption so,
duke@435:                             OopClosure* roots,
jrose@1424:                             CodeBlobClosure* code_roots,
coleenp@4037:                             KlassClosure* klass_closure);
duke@435: 
duke@435:   // Apply "blk" to all the weak roots of the system.  These include
duke@435:   // JNI weak roots, the code cache, system dictionary, symbol table,
duke@435:   // string table.
duke@435:   void process_weak_roots(OopClosure* root_closure,
jrose@1424:                           CodeBlobClosure* code_roots,
duke@435:                           OopClosure* non_root_closure);
duke@435: 
duke@435:   // The functions below are helper functions that a subclass of
duke@435:   // "SharedHeap" can use in the implementation of its virtual
duke@435:   // functions.
duke@435: 
ysr@777: public:
duke@435: 
duke@435:   // Do anything common to GC's.
duke@435:   virtual void gc_prologue(bool full) = 0;
duke@435:   virtual void gc_epilogue(bool full) = 0;
duke@435: 
jmasa@3294:   // Sets the number of parallel threads that will be doing tasks
jmasa@3294:   // (such as process strong roots) subsequently.
jmasa@3357:   virtual void set_par_threads(uint t);
jmasa@3294: 
jmasa@3294:   int n_termination();
jmasa@3294:   void set_n_termination(int t);
jmasa@3294: 
duke@435:   //
duke@435:   // New methods from CollectedHeap
duke@435:   //
duke@435: 
duke@435:   // Some utilities.
ysr@777:   void print_size_transition(outputStream* out,
ysr@777:                              size_t bytes_before,
duke@435:                              size_t bytes_after,
duke@435:                              size_t capacity);
duke@435: };
stefank@2314: 
stefank@2314: #endif // SHARE_VM_MEMORY_SHAREDHEAP_HPP