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/* EINA - EFL data type library
* Copyright (C) 2009 Jorge Luis Zapata Muga
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library;
* if not, see <http://www.gnu.org/licenses/>.
*/
/*
* This is a naive 'buddy' allocator following Knuth's documentation.
* The main difference is that we dont store the block information
* on the block memory itself but on another malloc'd area.
* This is useful for managing memory which isn't as fast as the main
* memory like the video memory
* The algorithm uses an area to store the linked list of blocks.
* Each block size is equal to the minimum allocatable block size for
* the memory pool and the number of blocks is equal to the size of the
* memory pool divided by the block size.
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include <stdio.h>
#include "eina_types.h"
#include "eina_inlist.h"
#include "eina_module.h"
#include "eina_mempool.h"
#include "eina_private.h"
typedef struct _Block
{
EINA_INLIST;
Eina_Bool available : 1;
unsigned short int order : 7; /* final order is order + min_order */
} Block;
typedef struct _Buddy
{
void *heap; /* start address of the heap */
size_t size; /* total size in bytes of the heap */
unsigned int min_order; /* minimum size is 1 << min_order */
unsigned int max_order; /* maximum size is 1 << max_order */
unsigned int num_order; /* number of orders */
Eina_Inlist **areas; /* one area per order */
Block *blocks; /* the allocated block information */
} Buddy;
/* get the minimum order greater or equal to size */
static inline unsigned int _get_order(Buddy *b, size_t size)
{
unsigned int i;
size_t bytes;
bytes = 1 << b->min_order;
for (i = 0; bytes < size && i < b->num_order; i++)
{
bytes += bytes;
}
//printf("order for size %d is %d\n", size, i + b->min_order);
return i;
}
static inline void *_get_offset(Buddy *b, Block *block)
{
void *ret;
ret = (char *)b->heap + ((block - &b->blocks[0]) << b->min_order);
return ret;
}
static void *_init(__UNUSED__ const char *context,
__UNUSED__ const char *options,
va_list args)
{
Buddy *b;
int i;
size_t bytes;
size_t size;
size_t min_order;
void *heap;
heap = va_arg(args, void *);
size = va_arg(args, size_t);
min_order = va_arg(args, int);
/* the minimum order we support is 15 (32K) */
min_order = min_order < 15 ? 15 : min_order;
bytes = 1 << min_order;
for (i = 0; bytes <= size; i++)
{
bytes += bytes;
}
if (!i)
return NULL;
b = malloc(sizeof(Buddy));
b->heap = heap;
b->size = size;
b->min_order = min_order;
b->max_order = min_order + i - 1;
b->num_order = i;
b->areas = calloc(b->num_order, sizeof(Eina_Inlist *));
b->blocks = calloc(1 << (b->num_order - 1), sizeof(Block));
/* setup the initial free area */
b->blocks[0].available = EINA_TRUE;
b->areas[b->num_order - 1] = EINA_INLIST_GET(&(b->blocks[0]));
return b;
}
static void _shutdown(void *data)
{
Buddy *b = data;
free(b->blocks);
free(b->areas);
free(b);
}
static void _free(void *data, void *element)
{
Buddy *b = data;
Block *block, *buddy;
size_t offset;
size_t idx;
offset = (unsigned char *)element - (unsigned char *)b->heap;
if (offset > b->size)
return;
idx = offset >> b->min_order;
block = &b->blocks[idx];
//printf("free %x idx = %d order = %d buddy = %d\n", offset, idx, block->order, idx ^ (1 << block->order));
/* we should always work with the buddy at right */
if (idx & (1 << block->order))
{
Block *left;
idx = idx ^ (1 << block->order);
left = &b->blocks[idx];
if (!left->available)
goto end;
else
{
buddy = block;
block = left;
b->areas[block->order] = eina_inlist_remove(b->areas[block->order],
EINA_INLIST_GET(block));
block->order++;
}
}
check:
/* already on the last order */
if (block->order + b->min_order == b->max_order)
{
goto end; /* get the buddy */
}
buddy = &b->blocks[idx ^ (1 << block->order)];
if (!buddy->available)
{
goto end; /* merge two blocks */
}
b->areas[block->order] = eina_inlist_remove(b->areas[block->order],
EINA_INLIST_GET(buddy));
block->order++;
goto check;
end:
/* add the block to the free list */
block->available = EINA_TRUE;
b->areas[block->order] = eina_inlist_append(b->areas[block->order],
EINA_INLIST_GET(block));
}
static void *_alloc(void *data, unsigned int size)
{
Buddy *b = data;
Block *block, *buddy;
unsigned int k, j;
k = j = _get_order(b, size);
/* get a free list of order k where k <= j <= max_order */
while ((j < b->num_order) && !b->areas[j])
j++;
/* check that the order is on our range */
if (j + b->min_order > b->max_order)
return NULL;
/* get a free element on this order, if not, go splitting until we find one */
//printf("getting order %d (%d) for size %d\n", j, k, size);
found:
if (j == k)
{
void *ret;
block = EINA_INLIST_CONTAINER_GET(b->areas[j], Block);
block->available = EINA_FALSE;
block->order = j;
/* remove the block from the list */
b->areas[j] = eina_inlist_remove(b->areas[j], EINA_INLIST_GET(block));
ret = _get_offset(b, block);
return ret;
}
block = EINA_INLIST_CONTAINER_GET(b->areas[j], Block);
/* split */
b->areas[j] = eina_inlist_remove(b->areas[j], EINA_INLIST_GET(block));
j--;
b->areas[j] = eina_inlist_append(b->areas[j], EINA_INLIST_GET(block));
buddy = block + (1 << j);
buddy->order = j;
buddy->available = EINA_TRUE;
b->areas[j] = eina_inlist_append(b->areas[j], EINA_INLIST_GET(buddy));
goto found;
}
static void _statistics(void *data)
{
Buddy *b = data;
unsigned int i;
printf("Information:\n");
printf(
"size = %zu, min_order = %d, max_order = %d, num_order = %d, num_blocks = %d (%uKB)\n",
b->size,
b->min_order,
b->max_order,
b->num_order,
1 << b->num_order,
((1 << (b->num_order)) * sizeof(Block)) / 1024);
printf("Area dumping:");
/* iterate over the free lists and dump the maps */
for (i = 0; i < b->num_order; i++)
{
Block *block;
printf("\n2^%d:", b->min_order + i);
EINA_INLIST_FOREACH(b->areas[i], block)
{
printf(" %d", (block - &b->blocks[0]));
}
}
printf("\nBlocks dumping:\n");
}
static Eina_Mempool_Backend _backend = {
"buddy",
&_init,
&_free,
&_alloc,
NULL, /* realloc */
NULL, /* garbage collect */
&_statistics,
&_shutdown,
NULL /* repack */
};
Eina_Bool buddy_init(void)
{
return eina_mempool_register(&_backend);
}
void buddy_shutdown(void)
{
eina_mempool_unregister(&_backend);
}
#ifndef EINA_STATIC_BUILD_BUDDY
EINA_MODULE_INIT(buddy_init);
EINA_MODULE_SHUTDOWN(buddy_shutdown);
#endif /* ! EINA_STATIC_BUILD_BUDDY */
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