1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
|
// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include "traits.h"
#include "arrayref.h"
#include "memoryusage.h"
#include <cstdlib>
#include <memory>
namespace vespalib {
namespace stash {
struct Cleanup {
Cleanup * const next;
explicit Cleanup(Cleanup *next_in) noexcept : next(next_in) {}
virtual void cleanup() = 0;
virtual size_t allocated() const noexcept { return 0; }
protected:
virtual ~Cleanup() = default;
};
// used as header for memory allocated outside the stash
struct DeleteMemory final : public Cleanup {
explicit DeleteMemory(size_t sz, Cleanup *next_in) noexcept : Cleanup(next_in), _allocated(sz) {}
void cleanup() override { free((void*)this); }
size_t allocated() const noexcept override { return _allocated; }
size_t _allocated;
};
// used as prefix for objects to be destructed
template<typename T>
struct DestructObject final : public Cleanup {
explicit DestructObject(Cleanup *next_in) noexcept : Cleanup(next_in) {}
void cleanup() override { reinterpret_cast<T*>(this + 1)->~T(); }
};
// used as prefix for arrays to be destructed
template<typename T>
struct DestructArray final : public Cleanup {
size_t size;
explicit DestructArray(Cleanup *next_in, size_t size_in) noexcept
: Cleanup(next_in), size(size_in) {}
void cleanup() override {
T *array = reinterpret_cast<T*>(this + 1);
for (size_t i = size; i-- > 0;) {
array[i].~T();
}
}
};
struct Chunk {
Chunk *next;
size_t used;
Chunk(const Chunk &) = delete;
explicit Chunk(Chunk *next_in) noexcept : next(next_in), used(sizeof(Chunk)) {}
void clear() noexcept { used = sizeof(Chunk); }
char *alloc(size_t size, size_t chunk_size) noexcept {
size_t aligned_size = ((size + (sizeof(char *) - 1))
& ~(sizeof(char *) - 1));
if (used + aligned_size > chunk_size) {
return nullptr;
}
char *ret = reinterpret_cast<char*>(this) + used;
used += aligned_size;
return ret;
}
};
} // namespace vespalib::stash
/**
* @brief A Stash stores mixed typed objects next to each other in
* memory.
*
* When a stash is destructed, destruction of internal objects will be
* performed in reverse creation order. Objects that satisfy the
* vespalib::can_skip_destruction concept are not destructed. This
* will save both time and space.
*
* The minimal chunk size of a stash is 4k. Any object larger than 1/4
* of the chunk size will be allocated separately.
**/
class Stash
{
private:
stash::Chunk *_chunks;
stash::Cleanup *_cleanup;
size_t _chunk_size;
char *do_alloc(size_t size);
bool is_small(size_t size) const noexcept { return (size < (_chunk_size / 4)); }
template <typename T, typename ... Args>
T *init_array(char *mem, size_t size, Args && ... args) {
T *array = reinterpret_cast<T*>(mem);
for (size_t i = 0; i < size; ++i) {
new (array + i) T(std::forward<Args>(args)...);
}
return array;
}
template <typename T>
T *copy_elements(char *mem, ConstArrayRef<T> src) {
T *array = reinterpret_cast<T*>(mem);
for (size_t i = 0; i < src.size(); ++i) {
new (array + i) T(src[i]);
}
return array;
}
public:
/**
* A mark denoting a specific stash state that can later be
* reverted to. Used with the 'mark' and 'revert' functions. Note
* that trying to revert to a mark that does not represent an
* earlier state of the appropriate stash yields undefined
* behavior. A default constructed mark can be used on any stash
* to revert it to its initial empty state.
**/
class Mark {
private:
friend class Stash;
stash::Cleanup *_cleanup;
stash::Chunk *_chunk;
size_t _used;
Mark(stash::Cleanup *cleanup, stash::Chunk *chunk) noexcept
: _cleanup(cleanup), _chunk(chunk), _used(chunk ? chunk->used : 0u) {}
public:
Mark() noexcept : Mark(nullptr, nullptr) {}
};
using UP = std::unique_ptr<Stash>;
explicit Stash(size_t chunk_size) noexcept ;
Stash() noexcept : Stash(4096) {}
Stash(Stash &&rhs) noexcept;
Stash(const Stash &) = delete;
Stash & operator = (const Stash &) = delete;
~Stash();
Stash &operator=(Stash &&rhs) noexcept;
void clear();
Mark mark() const noexcept { return Mark(_cleanup, _chunks); }
void revert(const Mark &mark);
size_t count_used() const;
size_t get_chunk_size() const { return _chunk_size; }
MemoryUsage get_memory_usage() const;
char *alloc(size_t size) {
char *ret = __builtin_expect(is_small(size) && _chunks != nullptr, true)
? _chunks->alloc(size, _chunk_size) : nullptr;
return __builtin_expect(ret != nullptr, true) ? ret : do_alloc(size);
}
template <typename T, typename ... Args>
T &create(Args && ... args) {
if (can_skip_destruction<T>) {
return *(new (alloc(sizeof(T))) T(std::forward<Args>(args)...));
}
using DeleteHook = stash::DestructObject<T>;
char *mem = alloc(sizeof(DeleteHook) + sizeof(T));
T *ret = new (mem + sizeof(DeleteHook)) T(std::forward<Args>(args)...);
_cleanup = new (mem) DeleteHook(_cleanup);
return *ret;
}
template <typename T, typename ... Args>
ArrayRef<T> create_array(size_t size, Args && ... args) {
if (can_skip_destruction<T>) {
return ArrayRef<T>(init_array<T, Args...>(alloc(size * sizeof(T)), size, std::forward<Args>(args)...), size);
}
using DeleteHook = stash::DestructArray<T>;
char *mem = alloc(sizeof(DeleteHook) + (size * sizeof(T)));
T *ret = init_array<T, Args...>(mem + sizeof(DeleteHook), size, std::forward<Args>(args)...);
_cleanup = new (mem) DeleteHook(_cleanup, size);
return ArrayRef<T>(ret, size);
}
template <typename T>
ArrayRef<T> create_uninitialized_array(size_t size) {
static_assert(std::is_trivially_copyable_v<T>);
static_assert(can_skip_destruction<T>);
return ArrayRef<T>(reinterpret_cast<T*>(alloc(size * sizeof(T))), size);
}
template <typename T>
ArrayRef<T> copy_array(ConstArrayRef<T> src) {
if (can_skip_destruction<T>) {
return ArrayRef<T>(copy_elements<T>(alloc(src.size() * sizeof(T)), src), src.size());
}
using DeleteHook = stash::DestructArray<T>;
char *mem = alloc(sizeof(DeleteHook) + (src.size() * sizeof(T)));
T *ret = copy_elements<T>(mem + sizeof(DeleteHook), src);
_cleanup = new (mem) DeleteHook(_cleanup, src.size());
return ArrayRef<T>(ret, src.size());
}
};
} // namespace vespalib
|
