1/*
2 * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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24
25#ifndef SHARE_VM_GC_SHARED_PLAB_HPP
26#define SHARE_VM_GC_SHARED_PLAB_HPP
27
28#include "gc/shared/gcUtil.hpp"
29#include "memory/allocation.hpp"
30#include "utilities/globalDefinitions.hpp"
31
32// Forward declarations.
33class PLABStats;
34
35// A per-thread allocation buffer used during GC.
36class PLAB: public CHeapObj<mtGC> {
37protected:
38  char      head[32];
39  size_t    _word_sz;          // In HeapWord units
40  HeapWord* _bottom;
41  HeapWord* _top;
42  HeapWord* _end;           // Last allocatable address + 1
43  HeapWord* _hard_end;      // _end + AlignmentReserve
44  // In support of ergonomic sizing of PLAB's
45  size_t    _allocated;     // in HeapWord units
46  size_t    _wasted;        // in HeapWord units
47  size_t    _undo_wasted;
48  char      tail[32];
49  static size_t AlignmentReserve;
50
51  // Force future allocations to fail and queries for contains()
52  // to return false. Returns the amount of unused space in this PLAB.
53  size_t invalidate() {
54    _end    = _hard_end;
55    size_t remaining = pointer_delta(_end, _top);  // Calculate remaining space.
56    _top    = _end;      // Force future allocations to fail.
57    _bottom = _end;      // Force future contains() queries to return false.
58    return remaining;
59  }
60
61  // Fill in remaining space with a dummy object and invalidate the PLAB. Returns
62  // the amount of remaining space.
63  size_t retire_internal();
64
65  void add_undo_waste(HeapWord* obj, size_t word_sz);
66
67  // Undo the last allocation in the buffer, which is required to be of the
68  // "obj" of the given "word_sz".
69  void undo_last_allocation(HeapWord* obj, size_t word_sz);
70
71public:
72  // Initializes the buffer to be empty, but with the given "word_sz".
73  // Must get initialized with "set_buf" for an allocation to succeed.
74  PLAB(size_t word_sz);
75  virtual ~PLAB() {}
76
77  static size_t size_required_for_allocation(size_t word_size) { return word_size + AlignmentReserve; }
78
79  // Minimum PLAB size.
80  static size_t min_size();
81  // Maximum PLAB size.
82  static size_t max_size();
83
84  // If an allocation of the given "word_sz" can be satisfied within the
85  // buffer, do the allocation, returning a pointer to the start of the
86  // allocated block.  If the allocation request cannot be satisfied,
87  // return NULL.
88  HeapWord* allocate(size_t word_sz) {
89    HeapWord* res = _top;
90    if (pointer_delta(_end, _top) >= word_sz) {
91      _top = _top + word_sz;
92      return res;
93    } else {
94      return NULL;
95    }
96  }
97
98  // Allocate the object aligned to "alignment_in_bytes".
99  inline HeapWord* allocate_aligned(size_t word_sz, unsigned short alignment_in_bytes);
100
101  // Undo any allocation in the buffer, which is required to be of the
102  // "obj" of the given "word_sz".
103  void undo_allocation(HeapWord* obj, size_t word_sz);
104
105  // The total (word) size of the buffer, including both allocated and
106  // unallocated space.
107  size_t word_sz() { return _word_sz; }
108
109  size_t waste() { return _wasted; }
110  size_t undo_waste() { return _undo_wasted; }
111
112  // The number of words of unallocated space remaining in the buffer.
113  size_t words_remaining() {
114    assert(_end >= _top, "Negative buffer");
115    return pointer_delta(_end, _top, HeapWordSize);
116  }
117
118  bool contains(void* addr) {
119    return (void*)_bottom <= addr && addr < (void*)_hard_end;
120  }
121
122  // Sets the space of the buffer to be [buf, space+word_sz()).
123  virtual void set_buf(HeapWord* buf, size_t new_word_sz) {
124    assert(new_word_sz > AlignmentReserve, "Too small");
125    _word_sz = new_word_sz;
126
127    _bottom   = buf;
128    _top      = _bottom;
129    _hard_end = _bottom + word_sz();
130    _end      = _hard_end - AlignmentReserve;
131    assert(_end >= _top, "Negative buffer");
132    // In support of ergonomic sizing
133    _allocated += word_sz();
134  }
135
136  // Flush allocation statistics into the given PLABStats supporting ergonomic
137  // sizing of PLAB's and retire the current buffer. To be called at the end of
138  // GC.
139  virtual void flush_and_retire_stats(PLABStats* stats);
140
141  // Fills in the unallocated portion of the buffer with a garbage object and updates
142  // statistics. To be called during GC.
143  virtual void retire();
144};
145
146// PLAB book-keeping.
147class PLABStats : public CHeapObj<mtGC> {
148 protected:
149  const char* _description;   // Identifying string.
150
151  size_t _allocated;          // Total allocated
152  size_t _wasted;             // of which wasted (internal fragmentation)
153  size_t _undo_wasted;        // of which wasted on undo (is not used for calculation of PLAB size)
154  size_t _unused;             // Unused in last buffer
155  size_t _desired_net_plab_sz;// Output of filter (below), suitably trimmed and quantized
156  AdaptiveWeightedAverage
157         _filter;             // Integrator with decay
158
159  virtual void reset() {
160    _allocated   = 0;
161    _wasted      = 0;
162    _undo_wasted = 0;
163    _unused      = 0;
164  }
165
166  virtual void log_plab_allocation();
167  virtual void log_sizing(size_t calculated, size_t net_desired);
168 public:
169  PLABStats(const char* description, size_t desired_net_plab_sz_, unsigned wt) :
170    _description(description),
171    _allocated(0),
172    _wasted(0),
173    _undo_wasted(0),
174    _unused(0),
175    _desired_net_plab_sz(desired_net_plab_sz_),
176    _filter(wt)
177  { }
178
179  virtual ~PLABStats() { }
180
181  size_t allocated() const { return _allocated; }
182  size_t wasted() const { return _wasted; }
183  size_t unused() const { return _unused; }
184  size_t used() const { return allocated() - (wasted() + unused()); }
185  size_t undo_wasted() const { return _undo_wasted; }
186
187  static const size_t min_size() {
188    return PLAB::min_size();
189  }
190
191  static const size_t max_size() {
192    return PLAB::max_size();
193  }
194
195  // Calculates plab size for current number of gc worker threads.
196  size_t desired_plab_sz(uint no_of_gc_workers);
197
198  // Updates the current desired PLAB size. Computes the new desired PLAB size with one gc worker thread,
199  // updates _desired_plab_sz and clears sensor accumulators.
200  virtual void adjust_desired_plab_sz();
201
202  inline void add_allocated(size_t v);
203
204  inline void add_unused(size_t v);
205
206  inline void add_wasted(size_t v);
207
208  inline void add_undo_wasted(size_t v);
209};
210
211#endif // SHARE_VM_GC_SHARED_PLAB_HPP
212