| /* |
| * Copyright (c) 2000, 2010, 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 |
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| * 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. |
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| |
| #ifndef SHARE_VM_MEMORY_SHAREDHEAP_HPP |
| #define SHARE_VM_MEMORY_SHAREDHEAP_HPP |
| |
| #include "gc_interface/collectedHeap.hpp" |
| #include "gc_implementation/shared/gcHeapSummary.hpp" |
| #include "memory/generation.hpp" |
| #include "memory/permGen.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 PermGen; |
| 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 KlassHandle; |
| |
| // 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 |
| // collecting_perm_gen, so, |
| // &buf_scan_non_heap_roots, |
| // &eager_scan_code_roots, |
| // &buf_scan_perm); |
| // 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(perm_gen(), perm_blk); |
| // 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; |
| |
| // All heaps contain a "permanent generation." This is some ways |
| // similar to a generation in a generational system, in other ways not. |
| // See the "PermGen" class. |
| PermGen* _perm_gen; |
| |
| // 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; } |
| |
| CollectorPolicy *collector_policy() const { return _collector_policy; } |
| |
| 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(); |
| |
| void set_perm(PermGen* perm_gen) { _perm_gen = perm_gen; } |
| |
| // This function returns the "GenRemSet" object that allows us to scan |
| // generations; at least the perm gen, possibly more in a fully |
| // generational heap. |
| GenRemSet* rem_set() { return _rem_set; } |
| |
| // These function return the "permanent" generation, in which |
| // reflective objects are allocated and stored. Two versions, the second |
| // of which returns the view of the perm gen as a generation. |
| PermGen* perm() const { return _perm_gen; } |
| Generation* perm_gen() const { return _perm_gen->as_gen(); } |
| |
| // Iteration functions. |
| void oop_iterate(OopClosure* cl) = 0; |
| |
| // Same as above, restricted to a memory region. |
| virtual void oop_iterate(MemRegion mr, OopClosure* cl) = 0; |
| |
| // Iterate over all objects allocated since the last collection, calling |
| // "cl->do_object" on each. The heap must have been initialized properly |
| // to support this function, or else this call will fail. |
| virtual void object_iterate_since_last_GC(ObjectClosure* 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. |
| // If "collecting_perm_gen" is false, then roots that may only contain |
| // references to permGen objects are not scanned; instead, in that case, |
| // the "perm_blk" closure is applied to all outgoing refs in the |
| // permanent generation. The "so" argument determines which of 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 collecting_perm_gen, |
| ScanningOption so, |
| OopClosure* roots, |
| CodeBlobClosure* code_roots, |
| OopsInGenClosure* perm_blk); |
| |
| // 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, |
| OopClosure* non_root_closure); |
| |
| // 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 |
| // |
| |
| size_t permanent_capacity() const { |
| assert(perm_gen(), "NULL perm gen"); |
| return perm_gen()->capacity(); |
| } |
| |
| size_t permanent_used() const { |
| assert(perm_gen(), "NULL perm gen"); |
| return perm_gen()->used(); |
| } |
| |
| VirtualSpaceSummary create_perm_gen_space_summary() { |
| HeapWord* start = perm_gen()->reserved().start(); |
| return VirtualSpaceSummary(start, (HeapWord*)((uintptr_t)start + perm_gen()->capacity()), perm_gen()->reserved().end()); |
| } |
| |
| bool is_in_permanent(const void *p) const { |
| assert(perm_gen(), "NULL perm gen"); |
| return perm_gen()->is_in_reserved(p); |
| } |
| |
| // Different from is_in_permanent in that is_in_permanent |
| // only checks if p is in the reserved area of the heap |
| // and this checks to see if it in the commited area. |
| // This is typically used by things like the forte stackwalker |
| // during verification of suspicious frame values. |
| bool is_permanent(const void *p) const { |
| assert(perm_gen(), "NULL perm gen"); |
| return perm_gen()->is_in(p); |
| } |
| |
| HeapWord* permanent_mem_allocate(size_t size) { |
| assert(perm_gen(), "NULL perm gen"); |
| return _perm_gen->mem_allocate(size); |
| } |
| |
| void permanent_oop_iterate(OopClosure* cl) { |
| assert(perm_gen(), "NULL perm gen"); |
| _perm_gen->oop_iterate(cl); |
| } |
| |
| void permanent_object_iterate(ObjectClosure* cl) { |
| assert(perm_gen(), "NULL perm gen"); |
| _perm_gen->object_iterate(cl); |
| } |
| |
| // 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 |