jdk8-mips64-public/hotspot: comparison src/share/vm/memory/sharedHeap.hpp

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+/*
+* 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
+* 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. 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
+//                       is_scavenging, so,
+//                       &buf_scan_non_heap_roots,
+//                       &eager_scan_code_roots);
+//  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()
+//  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;
+// 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);
+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();
+// 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;
+// Same as above, restricted to a memory region.
+virtual void oop_iterate(MemRegion mr, 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_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.
+// The "so" argument determines which 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 is_scavenging,
+ScanningOption so,
+OopClosure* roots,
+CodeBlobClosure* code_roots,
+KlassClosure* klass_closure);
+// 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);
+// 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
+//
+// 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

Mercurial > jdk8-mips64-public > hotspot / file comparison

comparison: src/share/vm/memory/sharedHeap.hpp

src/share/vm/memory/sharedHeap.hpp