view src/share/vm/memory/defNewGeneration.hpp @ 2368:dde920245681

6896099: Integrate CMS heap ergo with default heap sizing ergo 6627787: CMS: JVM refuses to start up with -Xms16m -Xmx16m 7000125: CMS: Anti-monotone young gen sizing with respect to maximum whole heap size specification 7027529: CMS: retire CMSUseOldDefaults flag Summary: Simplify CMS heap sizing code, relying on ergonomic initial sizing consistent with other collectors for the most part, controlling only young gen sizing to rein in pause times. Make CMS young gen sizing default statically cpu-dependant. Remove inconsistencies wrt generation sizing and policy code, allowing for the fixing for 6627787 and 7000125. For 7027529, retire the flag CMSUseOldDefaults which had been introduced as a bridge from JDK 5 to JDK 6 a number of years ago. Reviewed-by: brutisso, poonam
author ysr
date Wed, 16 Mar 2011 10:37:08 -0700
parents 74ee0db180fa
children b632e80fc9dc
line wrap: on
line source

/*
 * Copyright (c) 2001, 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
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 * questions.
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 */

#ifndef SHARE_VM_MEMORY_DEFNEWGENERATION_HPP
#define SHARE_VM_MEMORY_DEFNEWGENERATION_HPP

#include "gc_implementation/shared/ageTable.hpp"
#include "gc_implementation/shared/cSpaceCounters.hpp"
#include "gc_implementation/shared/generationCounters.hpp"
#include "memory/generation.inline.hpp"
#include "utilities/stack.hpp"

class EdenSpace;
class ContiguousSpace;
class ScanClosure;

// DefNewGeneration is a young generation containing eden, from- and
// to-space.

class DefNewGeneration: public Generation {
  friend class VMStructs;

protected:
  Generation* _next_gen;
  int         _tenuring_threshold;   // Tenuring threshold for next collection.
  ageTable    _age_table;
  // Size of object to pretenure in words; command line provides bytes
  size_t        _pretenure_size_threshold_words;

  ageTable*   age_table() { return &_age_table; }
  // Initialize state to optimistically assume no promotion failure will
  // happen.
  void   init_assuming_no_promotion_failure();
  // True iff a promotion has failed in the current collection.
  bool   _promotion_failed;
  bool   promotion_failed() { return _promotion_failed; }

  // Handling promotion failure.  A young generation collection
  // can fail if a live object cannot be copied out of its
  // location in eden or from-space during the collection.  If
  // a collection fails, the young generation is left in a
  // consistent state such that it can be collected by a
  // full collection.
  //   Before the collection
  //     Objects are in eden or from-space
  //     All roots into the young generation point into eden or from-space.
  //
  //   After a failed collection
  //     Objects may be in eden, from-space, or to-space
  //     An object A in eden or from-space may have a copy B
  //       in to-space.  If B exists, all roots that once pointed
  //       to A must now point to B.
  //     All objects in the young generation are unmarked.
  //     Eden, from-space, and to-space will all be collected by
  //       the full collection.
  void handle_promotion_failure(oop);

  // In the absence of promotion failure, we wouldn't look at "from-space"
  // objects after a young-gen collection.  When promotion fails, however,
  // the subsequent full collection will look at from-space objects:
  // therefore we must remove their forwarding pointers.
  void remove_forwarding_pointers();

  // Preserve the mark of "obj", if necessary, in preparation for its mark
  // word being overwritten with a self-forwarding-pointer.
  void   preserve_mark_if_necessary(oop obj, markOop m);
  void   preserve_mark(oop obj, markOop m);    // work routine used by the above

  // Together, these keep <object with a preserved mark, mark value> pairs.
  // They should always contain the same number of elements.
  Stack<oop>     _objs_with_preserved_marks;
  Stack<markOop> _preserved_marks_of_objs;

  // Promotion failure handling
  OopClosure *_promo_failure_scan_stack_closure;
  void set_promo_failure_scan_stack_closure(OopClosure *scan_stack_closure) {
    _promo_failure_scan_stack_closure = scan_stack_closure;
  }

  Stack<oop> _promo_failure_scan_stack;
  void drain_promo_failure_scan_stack(void);
  bool _promo_failure_drain_in_progress;

  // Performance Counters
  GenerationCounters*  _gen_counters;
  CSpaceCounters*      _eden_counters;
  CSpaceCounters*      _from_counters;
  CSpaceCounters*      _to_counters;

  // sizing information
  size_t               _max_eden_size;
  size_t               _max_survivor_size;

  // Allocation support
  bool _should_allocate_from_space;
  bool should_allocate_from_space() const {
    return _should_allocate_from_space;
  }
  void clear_should_allocate_from_space() {
    _should_allocate_from_space = false;
  }
  void set_should_allocate_from_space() {
    _should_allocate_from_space = true;
  }

 protected:
  // Spaces
  EdenSpace*       _eden_space;
  ContiguousSpace* _from_space;
  ContiguousSpace* _to_space;

  enum SomeProtectedConstants {
    // Generations are GenGrain-aligned and have size that are multiples of
    // GenGrain.
    MinFreeScratchWords = 100
  };

  // Return the size of a survivor space if this generation were of size
  // gen_size.
  size_t compute_survivor_size(size_t gen_size, size_t alignment) const {
    size_t n = gen_size / (SurvivorRatio + 2);
    return n > alignment ? align_size_down(n, alignment) : alignment;
  }

 public:  // was "protected" but caused compile error on win32
  class IsAliveClosure: public BoolObjectClosure {
    Generation* _g;
  public:
    IsAliveClosure(Generation* g);
    void do_object(oop p);
    bool do_object_b(oop p);
  };

  class KeepAliveClosure: public OopClosure {
  protected:
    ScanWeakRefClosure* _cl;
    CardTableRS* _rs;
    template <class T> void do_oop_work(T* p);
  public:
    KeepAliveClosure(ScanWeakRefClosure* cl);
    virtual void do_oop(oop* p);
    virtual void do_oop(narrowOop* p);
  };

  class FastKeepAliveClosure: public KeepAliveClosure {
  protected:
    HeapWord* _boundary;
    template <class T> void do_oop_work(T* p);
  public:
    FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl);
    virtual void do_oop(oop* p);
    virtual void do_oop(narrowOop* p);
  };

  class EvacuateFollowersClosure: public VoidClosure {
    GenCollectedHeap* _gch;
    int _level;
    ScanClosure* _scan_cur_or_nonheap;
    ScanClosure* _scan_older;
  public:
    EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
                             ScanClosure* cur, ScanClosure* older);
    void do_void();
  };

  class FastEvacuateFollowersClosure: public VoidClosure {
    GenCollectedHeap* _gch;
    int _level;
    DefNewGeneration* _gen;
    FastScanClosure* _scan_cur_or_nonheap;
    FastScanClosure* _scan_older;
  public:
    FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
                                 DefNewGeneration* gen,
                                 FastScanClosure* cur,
                                 FastScanClosure* older);
    void do_void();
  };

 public:
  DefNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level,
                   const char* policy="Copy");

  virtual Generation::Name kind() { return Generation::DefNew; }

  // Accessing spaces
  EdenSpace*       eden() const           { return _eden_space; }
  ContiguousSpace* from() const           { return _from_space;  }
  ContiguousSpace* to()   const           { return _to_space;    }

  virtual CompactibleSpace* first_compaction_space() const;

  // Space enquiries
  size_t capacity() const;
  size_t used() const;
  size_t free() const;
  size_t max_capacity() const;
  size_t capacity_before_gc() const;
  size_t unsafe_max_alloc_nogc() const;
  size_t contiguous_available() const;

  size_t max_eden_size() const              { return _max_eden_size; }
  size_t max_survivor_size() const          { return _max_survivor_size; }

  bool supports_inline_contig_alloc() const { return true; }
  HeapWord** top_addr() const;
  HeapWord** end_addr() const;

  // Thread-local allocation buffers
  bool supports_tlab_allocation() const { return true; }
  size_t tlab_capacity() const;
  size_t unsafe_max_tlab_alloc() const;

  // Grow the generation by the specified number of bytes.
  // The size of bytes is assumed to be properly aligned.
  // Return true if the expansion was successful.
  bool expand(size_t bytes);

  // DefNewGeneration cannot currently expand except at
  // a GC.
  virtual bool is_maximal_no_gc() const { return true; }

  // Iteration
  void object_iterate(ObjectClosure* blk);
  void object_iterate_since_last_GC(ObjectClosure* cl);

  void younger_refs_iterate(OopsInGenClosure* cl);

  void space_iterate(SpaceClosure* blk, bool usedOnly = false);

  // Allocation support
  virtual bool should_allocate(size_t word_size, bool is_tlab) {
    assert(UseTLAB || !is_tlab, "Should not allocate tlab");

    size_t overflow_limit    = (size_t)1 << (BitsPerSize_t - LogHeapWordSize);

    const bool non_zero      = word_size > 0;
    const bool overflows     = word_size >= overflow_limit;
    const bool check_too_big = _pretenure_size_threshold_words > 0;
    const bool not_too_big   = word_size < _pretenure_size_threshold_words;
    const bool size_ok       = is_tlab || !check_too_big || not_too_big;

    bool result = !overflows &&
                  non_zero   &&
                  size_ok;

    return result;
  }

  HeapWord* allocate(size_t word_size, bool is_tlab);
  HeapWord* allocate_from_space(size_t word_size);

  HeapWord* par_allocate(size_t word_size, bool is_tlab);

  // Prologue & Epilogue
  virtual void gc_prologue(bool full);
  virtual void gc_epilogue(bool full);

  // Save the tops for eden, from, and to
  virtual void record_spaces_top();

  // Doesn't require additional work during GC prologue and epilogue
  virtual bool performs_in_place_marking() const { return false; }

  // Accessing marks
  void save_marks();
  void reset_saved_marks();
  bool no_allocs_since_save_marks();

  // Need to declare the full complement of closures, whether we'll
  // override them or not, or get message from the compiler:
  //   oop_since_save_marks_iterate_nv hides virtual function...
#define DefNew_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
  void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);

  ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DECL)

#undef DefNew_SINCE_SAVE_MARKS_DECL

  // For non-youngest collection, the DefNewGeneration can contribute
  // "to-space".
  virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor,
                          size_t max_alloc_words);

  // Reset for contribution of "to-space".
  virtual void reset_scratch();

  // GC support
  virtual void compute_new_size();

  // Returns true if the collection is likely to be safely
  // completed. Even if this method returns true, a collection
  // may not be guaranteed to succeed, and the system should be
  // able to safely unwind and recover from that failure, albeit
  // at some additional cost. Override superclass's implementation.
  virtual bool collection_attempt_is_safe();

  virtual void collect(bool   full,
                       bool   clear_all_soft_refs,
                       size_t size,
                       bool   is_tlab);
  HeapWord* expand_and_allocate(size_t size,
                                bool is_tlab,
                                bool parallel = false);

  oop copy_to_survivor_space(oop old);
  int tenuring_threshold() { return _tenuring_threshold; }

  // Performance Counter support
  void update_counters();

  // Printing
  virtual const char* name() const;
  virtual const char* short_name() const { return "DefNew"; }

  bool must_be_youngest() const { return true; }
  bool must_be_oldest() const { return false; }

  // PrintHeapAtGC support.
  void print_on(outputStream* st) const;

  void verify(bool allow_dirty);

  bool promo_failure_scan_is_complete() const {
    return _promo_failure_scan_stack.is_empty();
  }

 protected:
  // If clear_space is true, clear the survivor spaces.  Eden is
  // cleared if the minimum size of eden is 0.  If mangle_space
  // is true, also mangle the space in debug mode.
  void compute_space_boundaries(uintx minimum_eden_size,
                                bool clear_space,
                                bool mangle_space);
  // Scavenge support
  void swap_spaces();
};

#endif // SHARE_VM_MEMORY_DEFNEWGENERATION_HPP