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
|
#include "Python.h"
#include "pyarena.h"
/* A simple arena block structure
Measurements with standard library modules suggest the average
allocation is about 20 bytes and that most compiles use a single
block.
*/
#define DEFAULT_BLOCK_SIZE 8192
typedef struct _block {
size_t ab_size;
size_t ab_offset;
struct _block *ab_next;
void *ab_mem;
} block;
/* The arena manages two kinds of memory, blocks of raw memory
and a list of PyObject* pointers. PyObjects are decrefed
when the arena is freed.
*/
struct _arena {
block *a_head;
block *a_cur;
PyObject *a_objects;
#if defined(Py_DEBUG)
/* Debug output */
size_t total_allocs;
size_t total_size;
size_t total_blocks;
size_t total_block_size;
size_t total_big_blocks;
#endif
};
static block *
block_new(size_t size)
{
/* Allocate header and block as one unit.
ab_mem points just past header. */
block *b = (block *)malloc(sizeof(block) + size);
if (!b)
return NULL;
b->ab_size = size;
b->ab_mem = (void *)(b + 1);
b->ab_next = NULL;
b->ab_offset = 0;
return b;
}
static void
block_free(block *b) {
while (b) {
block *next = b->ab_next;
free(b);
b = next;
}
}
static void *
block_alloc(block *b, size_t size)
{
void *p;
assert(b);
if (b->ab_offset + size > b->ab_size) {
/* If we need to allocate more memory than will fit in
the default block, allocate a one-off block that is
exactly the right size. */
/* TODO(jhylton): Think about space waste at end of block */
block *new = block_new(
size < DEFAULT_BLOCK_SIZE ?
DEFAULT_BLOCK_SIZE : size);
if (!new)
return NULL;
assert(!b->ab_next);
b->ab_next = new;
b = new;
}
assert(b->ab_offset + size <= b->ab_size);
p = (void *)(((char *)b->ab_mem) + b->ab_offset);
b->ab_offset += size;
return p;
}
PyArena *
PyArena_New()
{
PyArena* arena = (PyArena *)malloc(sizeof(PyArena));
if (!arena)
return NULL;
arena->a_head = block_new(DEFAULT_BLOCK_SIZE);
arena->a_cur = arena->a_head;
if (!arena->a_head) {
free((void *)arena);
return NULL;
}
arena->a_objects = PyList_New(0);
if (!arena->a_objects) {
block_free(arena->a_head);
free((void *)arena);
return NULL;
}
#if defined(Py_DEBUG)
arena->total_allocs = 0;
arena->total_size = 0;
arena->total_blocks = 1;
arena->total_block_size = DEFAULT_BLOCK_SIZE;
arena->total_big_blocks = 0;
#endif
return arena;
}
void
PyArena_Free(PyArena *arena)
{
assert(arena);
#if defined(Py_DEBUG)
/*
fprintf(stderr,
"alloc=%d size=%d blocks=%d block_size=%d big=%d objects=%d\n",
arena->total_allocs, arena->total_size, arena->total_blocks,
arena->total_block_size, arena->total_big_blocks,
PyList_Size(arena->a_objects));
*/
#endif
block_free(arena->a_head);
assert(arena->a_objects->ob_refcnt == 1);
Py_DECREF(arena->a_objects);
free(arena);
}
void *
PyArena_Malloc(PyArena *arena, size_t size)
{
void *p = block_alloc(arena->a_cur, size);
if (!p)
return NULL;
#if defined(Py_DEBUG)
arena->total_allocs++;
arena->total_size += size;
#endif
/* Reset cur if we allocated a new block. */
if (arena->a_cur->ab_next) {
arena->a_cur = arena->a_cur->ab_next;
#if defined(Py_DEBUG)
arena->total_blocks++;
arena->total_block_size += arena->a_cur->ab_size;
if (arena->a_cur->ab_size > DEFAULT_BLOCK_SIZE)
arena->total_big_blocks++;
#endif
}
return p;
}
int
PyArena_AddPyObject(PyArena *arena, PyObject *obj)
{
return PyList_Append(arena->a_objects, obj) >= 0;
}
|
