diff -r 1dbddb2a1971 -r 07146758775b hotspot/src/share/vm/memory/sharedHeap.hpp --- 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