| /* |
| * 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 |
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| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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| |
| #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_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; |
| |
| 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); |
| |
| // 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; |
| |
| // 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_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: |
| int strong_roots_parity() { return _strong_roots_parity; } |
| |
| // 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); |
| }; |
| friend class StrongRootsScope; |
| |
| private: |
| void change_strong_roots_parity(); |
| |
| 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); |
| |
| // |
| // 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 |