--- a/hotspot/src/share/vm/memory/sharedHeap.hpp Thu May 07 20:50:57 2015 -0700
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,213 +0,0 @@
-/*
- * Copyright (c) 2000, 2015, 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. G1RootProcessor and
-// GenCollectedHeap have SubTasksDone.
-// 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.
-//
-// Examples of using SubTasksDone and SequentialSubTasksDone:
-// G1RootProcessor and GenCollectedHeap::process_roots() use
-// SubTasksDone* _process_strong_tasks to claim tasks for workers
-//
-// GenCollectedHeap::gen_process_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_termination 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;
-
-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;
-
- // 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();
-
- // 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);
-
- // Does operations required after initialization has been done.
- virtual void post_initialize();
-
- // Initialization of ("weak") reference processing support
- virtual void ref_processing_init();
-
- // Iteration functions.
- void oop_iterate(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(); }
-
- // Note, the below comment needs to be updated to reflect the changes
- // introduced by JDK-8076225. This should be done as part of JDK-8076289.
- //
- //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_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_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".
- public:
-
- // Call these in sequential code around process_roots.
- // strong_roots_prologue calls change_strong_roots_parity, if
- // parallel tasks are enabled.
- class StrongRootsScope : public MarkingCodeBlobClosure::MarkScope {
- SharedHeap* _sh;
-
- public:
- StrongRootsScope(SharedHeap* heap, bool activate = true);
- ~StrongRootsScope();
- };
-
- private:
-
- public:
- FlexibleWorkGang* workers() const { return _workers; }
-
- // 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 roots) subsequently.
- virtual void set_par_threads(uint t);
-};
-
-#endif // SHARE_VM_MEMORY_SHAREDHEAP_HPP