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view src/share/vm/memory/sharedHeap.hpp @ 6308:1bb742086acd
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author | Gilles Duboscq <duboscq@ssw.jku.at> |
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date | Mon, 03 Sep 2012 12:52:41 +0200 |
parents | 441e946dc1af |
children | da91efe96a93 |
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/* * 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 * 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" #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(); } 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