author | stefank |
Thu, 01 Sep 2011 16:18:17 +0200 | |
changeset 10524 | 6594ca81279a |
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permissions | -rw-r--r-- |
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/* |
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* Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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* |
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*/ |
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#ifndef SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP |
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#define SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP |
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#include "memory/referencePolicy.hpp" |
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#include "oops/instanceRefKlass.hpp" |
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// ReferenceProcessor class encapsulates the per-"collector" processing |
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// of java.lang.Reference objects for GC. The interface is useful for supporting |
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// a generational abstraction, in particular when there are multiple |
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// generations that are being independently collected -- possibly |
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// concurrently and/or incrementally. Note, however, that the |
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// ReferenceProcessor class abstracts away from a generational setting |
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// by using only a heap interval (called "span" below), thus allowing |
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// its use in a straightforward manner in a general, non-generational |
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// setting. |
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// |
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// The basic idea is that each ReferenceProcessor object concerns |
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// itself with ("weak") reference processing in a specific "span" |
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// of the heap of interest to a specific collector. Currently, |
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// the span is a convex interval of the heap, but, efficiency |
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// apart, there seems to be no reason it couldn't be extended |
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// (with appropriate modifications) to any "non-convex interval". |
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// forward references |
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class ReferencePolicy; |
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class AbstractRefProcTaskExecutor; |
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class DiscoveredList; |
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class ReferenceProcessor : public CHeapObj { |
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protected: |
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MemRegion _span; // (right-open) interval of heap |
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// subject to wkref discovery |
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bool _discovering_refs; // true when discovery enabled |
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bool _discovery_is_atomic; // if discovery is atomic wrt |
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// other collectors in configuration |
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bool _discovery_is_mt; // true if reference discovery is MT. |
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// If true, setting "next" field of a discovered refs list requires |
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// write barrier(s). (Must be true if used in a collector in which |
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// elements of a discovered list may be moved during discovery: for |
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// example, a collector like Garbage-First that moves objects during a |
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// long-term concurrent marking phase that does weak reference |
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// discovery.) |
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bool _discovered_list_needs_barrier; |
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BarrierSet* _bs; // Cached copy of BarrierSet. |
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bool _enqueuing_is_done; // true if all weak references enqueued |
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bool _processing_is_mt; // true during phases when |
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// reference processing is MT. |
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int _next_id; // round-robin mod _num_q counter in |
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// support of work distribution |
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// For collectors that do not keep GC marking information |
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// in the object header, this field holds a closure that |
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// helps the reference processor determine the reachability |
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// of an oop (the field is currently initialized to NULL for |
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// all collectors but the CMS collector). |
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BoolObjectClosure* _is_alive_non_header; |
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// Soft ref clearing policies |
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// . the default policy |
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static ReferencePolicy* _default_soft_ref_policy; |
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// . the "clear all" policy |
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static ReferencePolicy* _always_clear_soft_ref_policy; |
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// . the current policy below is either one of the above |
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ReferencePolicy* _current_soft_ref_policy; |
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// The discovered ref lists themselves |
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// The active MT'ness degree of the queues below |
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int _num_q; |
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// The maximum MT'ness degree of the queues below |
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int _max_num_q; |
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// Arrays of lists of oops, one per thread |
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DiscoveredList* _discoveredSoftRefs; |
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DiscoveredList* _discoveredWeakRefs; |
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DiscoveredList* _discoveredFinalRefs; |
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DiscoveredList* _discoveredPhantomRefs; |
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public: |
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int num_q() { return _num_q; } |
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int max_num_q() { return _max_num_q; } |
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void set_active_mt_degree(int v) { _num_q = v; } |
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DiscoveredList* discovered_soft_refs() { return _discoveredSoftRefs; } |
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ReferencePolicy* setup_policy(bool always_clear) { |
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_current_soft_ref_policy = always_clear ? |
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_always_clear_soft_ref_policy : _default_soft_ref_policy; |
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_current_soft_ref_policy->setup(); // snapshot the policy threshold |
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return _current_soft_ref_policy; |
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} |
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public: |
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// Process references with a certain reachability level. |
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void process_discovered_reflist(DiscoveredList refs_lists[], |
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ReferencePolicy* policy, |
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bool clear_referent, |
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BoolObjectClosure* is_alive, |
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OopClosure* keep_alive, |
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VoidClosure* complete_gc, |
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AbstractRefProcTaskExecutor* task_executor); |
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void process_phaseJNI(BoolObjectClosure* is_alive, |
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OopClosure* keep_alive, |
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VoidClosure* complete_gc); |
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// Work methods used by the method process_discovered_reflist |
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// Phase1: keep alive all those referents that are otherwise |
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// dead but which must be kept alive by policy (and their closure). |
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void process_phase1(DiscoveredList& refs_list, |
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ReferencePolicy* policy, |
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BoolObjectClosure* is_alive, |
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OopClosure* keep_alive, |
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VoidClosure* complete_gc); |
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// Phase2: remove all those references whose referents are |
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// reachable. |
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inline void process_phase2(DiscoveredList& refs_list, |
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BoolObjectClosure* is_alive, |
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OopClosure* keep_alive, |
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VoidClosure* complete_gc) { |
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if (discovery_is_atomic()) { |
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// complete_gc is ignored in this case for this phase |
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pp2_work(refs_list, is_alive, keep_alive); |
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} else { |
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assert(complete_gc != NULL, "Error"); |
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pp2_work_concurrent_discovery(refs_list, is_alive, |
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keep_alive, complete_gc); |
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} |
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} |
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// Work methods in support of process_phase2 |
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void pp2_work(DiscoveredList& refs_list, |
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BoolObjectClosure* is_alive, |
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OopClosure* keep_alive); |
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void pp2_work_concurrent_discovery( |
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DiscoveredList& refs_list, |
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BoolObjectClosure* is_alive, |
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OopClosure* keep_alive, |
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VoidClosure* complete_gc); |
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// Phase3: process the referents by either clearing them |
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// or keeping them alive (and their closure) |
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void process_phase3(DiscoveredList& refs_list, |
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bool clear_referent, |
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BoolObjectClosure* is_alive, |
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OopClosure* keep_alive, |
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VoidClosure* complete_gc); |
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// Enqueue references with a certain reachability level |
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void enqueue_discovered_reflist(DiscoveredList& refs_list, HeapWord* pending_list_addr); |
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// "Preclean" all the discovered reference lists |
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// by removing references with strongly reachable referents. |
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// The first argument is a predicate on an oop that indicates |
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// its (strong) reachability and the second is a closure that |
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// may be used to incrementalize or abort the precleaning process. |
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// The caller is responsible for taking care of potential |
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// interference with concurrent operations on these lists |
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// (or predicates involved) by other threads. Currently |
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// only used by the CMS collector. should_unload_classes is |
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// used to aid assertion checking when classes are collected. |
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void preclean_discovered_references(BoolObjectClosure* is_alive, |
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OopClosure* keep_alive, |
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VoidClosure* complete_gc, |
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YieldClosure* yield, |
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bool should_unload_classes); |
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// Delete entries in the discovered lists that have |
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// either a null referent or are not active. Such |
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// Reference objects can result from the clearing |
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// or enqueueing of Reference objects concurrent |
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// with their discovery by a (concurrent) collector. |
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// For a definition of "active" see java.lang.ref.Reference; |
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// Refs are born active, become inactive when enqueued, |
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// and never become active again. The state of being |
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// active is encoded as follows: A Ref is active |
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// if and only if its "next" field is NULL. |
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void clean_up_discovered_references(); |
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void clean_up_discovered_reflist(DiscoveredList& refs_list); |
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// Returns the name of the discovered reference list |
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// occupying the i / _num_q slot. |
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const char* list_name(int i); |
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void enqueue_discovered_reflists(HeapWord* pending_list_addr, AbstractRefProcTaskExecutor* task_executor); |
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protected: |
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// "Preclean" the given discovered reference list |
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// by removing references with strongly reachable referents. |
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// Currently used in support of CMS only. |
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void preclean_discovered_reflist(DiscoveredList& refs_list, |
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BoolObjectClosure* is_alive, |
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OopClosure* keep_alive, |
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VoidClosure* complete_gc, |
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YieldClosure* yield); |
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// round-robin mod _num_q (not: _not_ mode _max_num_q) |
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int next_id() { |
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int id = _next_id; |
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if (++_next_id == _num_q) { |
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_next_id = 0; |
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} |
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return id; |
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} |
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DiscoveredList* get_discovered_list(ReferenceType rt); |
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inline void add_to_discovered_list_mt(DiscoveredList& refs_list, oop obj, |
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HeapWord* discovered_addr); |
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void verify_ok_to_handle_reflists() PRODUCT_RETURN; |
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void clear_discovered_references(DiscoveredList& refs_list); |
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void abandon_partial_discovered_list(DiscoveredList& refs_list); |
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// Calculate the number of jni handles. |
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unsigned int count_jni_refs(); |
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// Balances reference queues. |
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void balance_queues(DiscoveredList ref_lists[]); |
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// Update (advance) the soft ref master clock field. |
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void update_soft_ref_master_clock(); |
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public: |
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// constructor |
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ReferenceProcessor(): |
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_span((HeapWord*)NULL, (HeapWord*)NULL), |
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_discoveredSoftRefs(NULL), _discoveredWeakRefs(NULL), |
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_discoveredFinalRefs(NULL), _discoveredPhantomRefs(NULL), |
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_discovering_refs(false), |
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_discovery_is_atomic(true), |
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_enqueuing_is_done(false), |
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_discovery_is_mt(false), |
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_discovered_list_needs_barrier(false), |
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_bs(NULL), |
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_is_alive_non_header(NULL), |
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_num_q(0), |
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_max_num_q(0), |
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_processing_is_mt(false), |
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_next_id(0) |
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{ } |
1 | 259 |
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// Default parameters give you a vanilla reference processor. |
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ReferenceProcessor(MemRegion span, |
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bool mt_processing = false, int mt_processing_degree = 1, |
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bool mt_discovery = false, int mt_discovery_degree = 1, |
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bool atomic_discovery = true, |
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BoolObjectClosure* is_alive_non_header = NULL, |
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bool discovered_list_needs_barrier = false); |
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1 | 268 |
// RefDiscoveryPolicy values |
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enum DiscoveryPolicy { |
1 | 270 |
ReferenceBasedDiscovery = 0, |
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ReferentBasedDiscovery = 1, |
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DiscoveryPolicyMin = ReferenceBasedDiscovery, |
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DiscoveryPolicyMax = ReferentBasedDiscovery |
1 | 274 |
}; |
275 |
||
276 |
static void init_statics(); |
|
277 |
||
278 |
public: |
|
279 |
// get and set "is_alive_non_header" field |
|
280 |
BoolObjectClosure* is_alive_non_header() { |
|
281 |
return _is_alive_non_header; |
|
282 |
} |
|
283 |
void set_is_alive_non_header(BoolObjectClosure* is_alive_non_header) { |
|
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_is_alive_non_header = is_alive_non_header; |
|
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} |
|
286 |
||
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// get and set span |
|
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MemRegion span() { return _span; } |
|
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void set_span(MemRegion span) { _span = span; } |
|
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// start and stop weak ref discovery |
|
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void enable_discovery() { _discovering_refs = true; } |
|
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void disable_discovery() { _discovering_refs = false; } |
|
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bool discovery_enabled() { return _discovering_refs; } |
|
295 |
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// whether discovery is atomic wrt other collectors |
|
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bool discovery_is_atomic() const { return _discovery_is_atomic; } |
|
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void set_atomic_discovery(bool atomic) { _discovery_is_atomic = atomic; } |
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// whether discovery is done by multiple threads same-old-timeously |
|
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bool discovery_is_mt() const { return _discovery_is_mt; } |
|
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void set_mt_discovery(bool mt) { _discovery_is_mt = mt; } |
|
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// Whether we are in a phase when _processing_ is MT. |
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bool processing_is_mt() const { return _processing_is_mt; } |
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void set_mt_processing(bool mt) { _processing_is_mt = mt; } |
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307 |
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// whether all enqueuing of weak references is complete |
|
309 |
bool enqueuing_is_done() { return _enqueuing_is_done; } |
|
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void set_enqueuing_is_done(bool v) { _enqueuing_is_done = v; } |
|
311 |
||
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// iterate over oops |
|
313 |
void weak_oops_do(OopClosure* f); // weak roots |
|
314 |
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// Balance each of the discovered lists. |
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void balance_all_queues(); |
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|
1 | 318 |
// Discover a Reference object, using appropriate discovery criteria |
319 |
bool discover_reference(oop obj, ReferenceType rt); |
|
320 |
||
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// Process references found during GC (called by the garbage collector) |
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void process_discovered_references(BoolObjectClosure* is_alive, |
1 | 323 |
OopClosure* keep_alive, |
324 |
VoidClosure* complete_gc, |
|
325 |
AbstractRefProcTaskExecutor* task_executor); |
|
326 |
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public: |
|
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// Enqueue references at end of GC (called by the garbage collector) |
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bool enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor = NULL); |
|
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// If a discovery is in process that is being superceded, abandon it: all |
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// the discovered lists will be empty, and all the objects on them will |
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// have NULL discovered fields. Must be called only at a safepoint. |
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void abandon_partial_discovery(); |
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|
1 | 336 |
// debugging |
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void verify_no_references_recorded() PRODUCT_RETURN; |
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void verify_referent(oop obj) PRODUCT_RETURN; |
1 | 339 |
|
340 |
// clear the discovered lists (unlinking each entry). |
|
341 |
void clear_discovered_references() PRODUCT_RETURN; |
|
342 |
}; |
|
343 |
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344 |
// A utility class to disable reference discovery in |
|
345 |
// the scope which contains it, for given ReferenceProcessor. |
|
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class NoRefDiscovery: StackObj { |
|
347 |
private: |
|
348 |
ReferenceProcessor* _rp; |
|
349 |
bool _was_discovering_refs; |
|
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public: |
|
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NoRefDiscovery(ReferenceProcessor* rp) : _rp(rp) { |
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_was_discovering_refs = _rp->discovery_enabled(); |
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if (_was_discovering_refs) { |
1 | 354 |
_rp->disable_discovery(); |
355 |
} |
|
356 |
} |
|
357 |
||
358 |
~NoRefDiscovery() { |
|
359 |
if (_was_discovering_refs) { |
|
360 |
_rp->enable_discovery(); |
|
361 |
} |
|
362 |
} |
|
363 |
}; |
|
364 |
||
365 |
||
366 |
// A utility class to temporarily mutate the span of the |
|
367 |
// given ReferenceProcessor in the scope that contains it. |
|
368 |
class ReferenceProcessorSpanMutator: StackObj { |
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369 |
private: |
|
370 |
ReferenceProcessor* _rp; |
|
371 |
MemRegion _saved_span; |
|
372 |
||
373 |
public: |
|
374 |
ReferenceProcessorSpanMutator(ReferenceProcessor* rp, |
|
375 |
MemRegion span): |
|
376 |
_rp(rp) { |
|
377 |
_saved_span = _rp->span(); |
|
378 |
_rp->set_span(span); |
|
379 |
} |
|
380 |
||
381 |
~ReferenceProcessorSpanMutator() { |
|
382 |
_rp->set_span(_saved_span); |
|
383 |
} |
|
384 |
}; |
|
385 |
||
386 |
// A utility class to temporarily change the MT'ness of |
|
387 |
// reference discovery for the given ReferenceProcessor |
|
388 |
// in the scope that contains it. |
|
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class ReferenceProcessorMTDiscoveryMutator: StackObj { |
1 | 390 |
private: |
391 |
ReferenceProcessor* _rp; |
|
392 |
bool _saved_mt; |
|
393 |
||
394 |
public: |
|
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ReferenceProcessorMTDiscoveryMutator(ReferenceProcessor* rp, |
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bool mt): |
1 | 397 |
_rp(rp) { |
398 |
_saved_mt = _rp->discovery_is_mt(); |
|
399 |
_rp->set_mt_discovery(mt); |
|
400 |
} |
|
401 |
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402 |
~ReferenceProcessorMTDiscoveryMutator() { |
1 | 403 |
_rp->set_mt_discovery(_saved_mt); |
404 |
} |
|
405 |
}; |
|
406 |
||
407 |
||
408 |
// A utility class to temporarily change the disposition |
|
409 |
// of the "is_alive_non_header" closure field of the |
|
410 |
// given ReferenceProcessor in the scope that contains it. |
|
411 |
class ReferenceProcessorIsAliveMutator: StackObj { |
|
412 |
private: |
|
413 |
ReferenceProcessor* _rp; |
|
414 |
BoolObjectClosure* _saved_cl; |
|
415 |
||
416 |
public: |
|
417 |
ReferenceProcessorIsAliveMutator(ReferenceProcessor* rp, |
|
418 |
BoolObjectClosure* cl): |
|
419 |
_rp(rp) { |
|
420 |
_saved_cl = _rp->is_alive_non_header(); |
|
421 |
_rp->set_is_alive_non_header(cl); |
|
422 |
} |
|
423 |
||
424 |
~ReferenceProcessorIsAliveMutator() { |
|
425 |
_rp->set_is_alive_non_header(_saved_cl); |
|
426 |
} |
|
427 |
}; |
|
428 |
||
429 |
// A utility class to temporarily change the disposition |
|
430 |
// of the "discovery_is_atomic" field of the |
|
431 |
// given ReferenceProcessor in the scope that contains it. |
|
432 |
class ReferenceProcessorAtomicMutator: StackObj { |
|
433 |
private: |
|
434 |
ReferenceProcessor* _rp; |
|
435 |
bool _saved_atomic_discovery; |
|
436 |
||
437 |
public: |
|
438 |
ReferenceProcessorAtomicMutator(ReferenceProcessor* rp, |
|
439 |
bool atomic): |
|
440 |
_rp(rp) { |
|
441 |
_saved_atomic_discovery = _rp->discovery_is_atomic(); |
|
442 |
_rp->set_atomic_discovery(atomic); |
|
443 |
} |
|
444 |
||
445 |
~ReferenceProcessorAtomicMutator() { |
|
446 |
_rp->set_atomic_discovery(_saved_atomic_discovery); |
|
447 |
} |
|
448 |
}; |
|
449 |
||
450 |
||
451 |
// A utility class to temporarily change the MT processing |
|
452 |
// disposition of the given ReferenceProcessor instance |
|
453 |
// in the scope that contains it. |
|
454 |
class ReferenceProcessorMTProcMutator: StackObj { |
|
455 |
private: |
|
456 |
ReferenceProcessor* _rp; |
|
457 |
bool _saved_mt; |
|
458 |
||
459 |
public: |
|
460 |
ReferenceProcessorMTProcMutator(ReferenceProcessor* rp, |
|
461 |
bool mt): |
|
462 |
_rp(rp) { |
|
463 |
_saved_mt = _rp->processing_is_mt(); |
|
464 |
_rp->set_mt_processing(mt); |
|
465 |
} |
|
466 |
||
467 |
~ReferenceProcessorMTProcMutator() { |
|
468 |
_rp->set_mt_processing(_saved_mt); |
|
469 |
} |
|
470 |
}; |
|
471 |
||
472 |
||
473 |
// This class is an interface used to implement task execution for the |
|
474 |
// reference processing. |
|
475 |
class AbstractRefProcTaskExecutor { |
|
476 |
public: |
|
477 |
||
478 |
// Abstract tasks to execute. |
|
479 |
class ProcessTask; |
|
480 |
class EnqueueTask; |
|
481 |
||
482 |
// Executes a task using worker threads. |
|
483 |
virtual void execute(ProcessTask& task) = 0; |
|
484 |
virtual void execute(EnqueueTask& task) = 0; |
|
485 |
||
486 |
// Switch to single threaded mode. |
|
487 |
virtual void set_single_threaded_mode() { }; |
|
488 |
}; |
|
489 |
||
490 |
// Abstract reference processing task to execute. |
|
491 |
class AbstractRefProcTaskExecutor::ProcessTask { |
|
492 |
protected: |
|
493 |
ProcessTask(ReferenceProcessor& ref_processor, |
|
494 |
DiscoveredList refs_lists[], |
|
495 |
bool marks_oops_alive) |
|
496 |
: _ref_processor(ref_processor), |
|
497 |
_refs_lists(refs_lists), |
|
498 |
_marks_oops_alive(marks_oops_alive) |
|
499 |
{ } |
|
500 |
||
501 |
public: |
|
502 |
virtual void work(unsigned int work_id, BoolObjectClosure& is_alive, |
|
503 |
OopClosure& keep_alive, |
|
504 |
VoidClosure& complete_gc) = 0; |
|
505 |
||
506 |
// Returns true if a task marks some oops as alive. |
|
507 |
bool marks_oops_alive() const |
|
508 |
{ return _marks_oops_alive; } |
|
509 |
||
510 |
protected: |
|
511 |
ReferenceProcessor& _ref_processor; |
|
512 |
DiscoveredList* _refs_lists; |
|
513 |
const bool _marks_oops_alive; |
|
514 |
}; |
|
515 |
||
516 |
// Abstract reference processing task to execute. |
|
517 |
class AbstractRefProcTaskExecutor::EnqueueTask { |
|
518 |
protected: |
|
519 |
EnqueueTask(ReferenceProcessor& ref_processor, |
|
520 |
DiscoveredList refs_lists[], |
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521 |
HeapWord* pending_list_addr, |
1 | 522 |
int n_queues) |
523 |
: _ref_processor(ref_processor), |
|
524 |
_refs_lists(refs_lists), |
|
525 |
_pending_list_addr(pending_list_addr), |
|
526 |
_n_queues(n_queues) |
|
527 |
{ } |
|
528 |
||
529 |
public: |
|
530 |
virtual void work(unsigned int work_id) = 0; |
|
531 |
||
532 |
protected: |
|
533 |
ReferenceProcessor& _ref_processor; |
|
534 |
DiscoveredList* _refs_lists; |
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HeapWord* _pending_list_addr; |
1 | 536 |
int _n_queues; |
537 |
}; |
|
7397 | 538 |
|
539 |
#endif // SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP |