Staging
v0.8.1
v0.8.1
https://github.com/python/cpython
Tip revision: 74f4bd53e03ded8408bcc2de67cf0f5a4ac5b1a1 authored by Barry Warsaw on 23 February 2012, 15:59:38 UTC
Bump some more copyright years (as per PEP 101), since this is the first
Bump some more copyright years (as per PEP 101), since this is the first
Tip revision: 74f4bd5
pyarena.c
#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.
TODO(jhylton): Think about a realloc API, maybe just for the last
allocation?
*/
#define DEFAULT_BLOCK_SIZE 8192
#define ALIGNMENT 8
#define ALIGNMENT_MASK (ALIGNMENT - 1)
#define ROUNDUP(x) (((x) + ALIGNMENT_MASK) & ~ALIGNMENT_MASK)
typedef struct _block {
/* Total number of bytes owned by this block available to pass out.
* Read-only after initialization. The first such byte starts at
* ab_mem.
*/
size_t ab_size;
/* Total number of bytes already passed out. The next byte available
* to pass out starts at ab_mem + ab_offset.
*/
size_t ab_offset;
/* An arena maintains a singly-linked, NULL-terminated list of
* all blocks owned by the arena. These are linked via the
* ab_next member.
*/
struct _block *ab_next;
/* Pointer to the first allocatable byte owned by this block. Read-
* only after initialization.
*/
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 {
/* Pointer to the first block allocated for the arena, never NULL.
It is used only to find the first block when the arena is
being freed.
*/
block *a_head;
/* Pointer to the block currently used for allocation. It's
ab_next field should be NULL. If it is not-null after a
call to block_alloc(), it means a new block has been allocated
and a_cur should be reset to point it.
*/
block *a_cur;
/* A Python list object containing references to all the PyObject
pointers associated with this area. They will be DECREFed
when the arena is freed.
*/
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 = ROUNDUP((Py_uintptr_t)(b->ab_mem)) -
(Py_uintptr_t)(b->ab_mem);
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);
size = ROUNDUP(size);
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 *newbl = block_new(
size < DEFAULT_BLOCK_SIZE ?
DEFAULT_BLOCK_SIZE : size);
if (!newbl)
return NULL;
assert(!b->ab_next);
b->ab_next = newbl;
b = newbl;
}
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 (PyArena*)PyErr_NoMemory();
arena->a_head = block_new(DEFAULT_BLOCK_SIZE);
arena->a_cur = arena->a_head;
if (!arena->a_head) {
free((void *)arena);
return (PyArena*)PyErr_NoMemory();
}
arena->a_objects = PyList_New(0);
if (!arena->a_objects) {
block_free(arena->a_head);
free((void *)arena);
return (PyArena*)PyErr_NoMemory();
}
#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)
{
int r;
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);
/* This property normally holds, except when the code being compiled
is sys.getobjects(0), in which case there will be two references.
assert(arena->a_objects->ob_refcnt == 1);
*/
/* Clear all the elements from the list. This is necessary
to guarantee that they will be DECREFed. */
r = PyList_SetSlice(arena->a_objects,
0, PyList_GET_SIZE(arena->a_objects), NULL);
assert(r == 0);
assert(PyList_GET_SIZE(arena->a_objects) == 0);
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 PyErr_NoMemory();
#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)
{
int r = PyList_Append(arena->a_objects, obj);
if (r >= 0) {
Py_DECREF(obj);
}
return r;
}