/*
* SLOB Allocator: Simple List Of Blocks
*
* Matt Mackall <mpm@selenic.com> 12/30/03
*
* How SLOB works:
*
* The core of SLOB is a traditional K&R style heap allocator, with
* support for returning aligned objects. The granularity of this
* allocator is 8 bytes on x86, though it's perhaps possible to reduce
* this to 4 if it's deemed worth the effort. The slob heap is a
* singly-linked list of pages from __get_free_page, grown on demand
* and allocation from the heap is currently first-fit.
*
* Above this is an implementation of kmalloc/kfree. Blocks returned
* from kmalloc are 8-byte aligned and prepended with a 8-byte header.
* If kmalloc is asked for objects of PAGE_SIZE or larger, it calls
* __get_free_pages directly so that it can return page-aligned blocks
* and keeps a linked list of such pages and their orders. These
* objects are detected in kfree() by their page alignment.
*
* SLAB is emulated on top of SLOB by simply calling constructors and
* destructors for every SLAB allocation. Objects are returned with
* the 8-byte alignment unless the SLAB_MUST_HWCACHE_ALIGN flag is
* set, in which case the low-level allocator will fragment blocks to
* create the proper alignment. Again, objects of page-size or greater
* are allocated by calling __get_free_pages. As SLAB objects know
* their size, no separate size bookkeeping is necessary and there is
* essentially no allocation space overhead.
*/
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/cache.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/timer.h>
struct slob_block {
int units;
struct slob_block *next;
};
typedef struct slob_block slob_t;
#define SLOB_UNIT sizeof(slob_t)
#define SLOB_UNITS(size) (((size) + SLOB_UNIT - 1)/SLOB_UNIT)
#define SLOB_ALIGN L1_CACHE_BYTES
struct bigblock {
int order;
void *pages;
struct bigblock *next;
};
typedef struct bigblock bigblock_t;
static slob_t arena = { .next = &arena, .units = 1 };
static slob_t *slobfree = &arena;
static bigblock_t *bigblocks;
static DEFINE_SPINLOCK(slob_lock);
static DEFINE_SPINLOCK(block_lock);
static void slob_free(void *b, int size);
static void slob_timer_cbk(void);
static void *slob_alloc(size_t size, gfp_t gfp, int align)
{
slob_t *prev, *cur, *aligned = 0;
int delta = 0, units = SLOB_UNITS(size);
unsigned long flags;
spin_lock_irqsave(&slob_lock, flags);
prev = slobfree;
for (cur = prev->next; ; prev = cur, cur = cur->next) {
if (align) {
aligned = (slob_t *)ALIGN((unsigned long)cur, align);
delta = aligned - cur;
}
if (cur->units >= units + delta) { /* room enough? */
if (delta) { /* need to fragment head to align? */
aligned->units = cur->units - delta;
aligned->next = cur->next;
cur->next = aligned;
cur->units = delta;
prev = cur;
cur = aligned;
}
if (cur->units == units) /* exact fit? */
prev->next = cur->next; /* unlink */
else { /* fragment */
prev->next = cur + units;
prev->next->units = cur->units - units;
prev->next->next = cur->next;
cur->units = units;
}
slobfree = prev;
spin_unlock_irqrestore(&slob_lock, flags);
return cur;
}
if (cur == slobfree) {
spin_unlock_irqrestore(&slob_lock, flags);
if (size == PAGE_SIZE) /* trying to shrink arena? */
return 0;
cur = (slob_t *)__get_free_page(gfp);
if (!cur)
return 0;
slob_free(cur, PAGE_SIZE);
spin_lock_irqsave(&slob_lock, flags);
cur = slobfree;
}
}
}
static void slob_free(void *block, int size)
{
slob_t *cur, *b = (slob_t *)block;
unsigned long flags;
if (!block)
return;
if (size)
b->units = SLOB_UNITS(size);
/* Find reinsertion point */
spin_lock_irqsave(&slob_lock, flags);
for (cur = slobfree; !(b > cur && b < cur->next); cur = cur->next)
if (cur >= cur->next && (b > cur || b < cur->next))
break;
if (b + b->units == cur->next) {
b->units += cur->next->units;
b->next = cur->next->next;
} else
b->next = cur->next;
if (cur + cur->units == b) {
cur->units += b->units;
cur->next = b->next;
} else
cur->next = b;
slobfree = cur;
spin_unlock_irqrestore(&slob_lock, flags);
}
static int FASTCALL(find_order(int size));
static int fastcall find_order(int size)
{
int order = 0;
for ( ; size > 4096 ; size >>=1)
order++;
return order;
}
void *__kmalloc(size_t size, gfp_t gfp)
{
slob_t *m;
bigblock_t *bb;
unsigned long flags;
if (size < PAGE_SIZE - SLOB_UNIT) {
m = slob_alloc(size + SLOB_UNIT, gfp, 0);
return m ? (void *)(m + 1) : 0;
}
bb = slob_alloc(sizeof(bigblock_t), gfp, 0);
if (!bb)
return 0;
bb->order = find_order(size);
bb->pages = (void *)__get_free_pages(gfp, bb->order);
if (bb->pages) {
spin_lock_irqsave(&block_lock, flags);
bb->next = bigblocks;
bigblocks = bb;
spin_unlock_irqrestore(&block_lock, flags);
return bb->pages;
}
slob_free(bb, sizeof(bigblock_t));
return 0;
}
EXPORT_SYMBOL(__kmalloc);
void kfree(const void *block)
{
bigblock_t *bb, **last = &bigblocks;
unsigned long flags;
if (!block)
return;
if (!((unsigned long)block & (PAGE_SIZE-1))) {
/* might be on the big block list */
spin_lock_irqsave(&block_lock, flags);
for (bb = bigblocks; bb; last = &bb->next, bb = bb->next) {
if (bb->pages == block) {
*last = bb->next;
spin_unlock_irqrestore(&block_lock, flags);
free_pages((unsigned long)block, bb->order);
slob_free(bb, sizeof(bigblock_t));
return;
}
}
spin_unlock_irqrestore(&block_lock, flags);
}
slob_free((slob_t *)block - 1, 0);
return;
}
EXPORT_SYMBOL(kfree);
unsigned int ksize(const void *block)
{
bigblock_t *bb;
unsigned long flags;
if (!block)
return 0;
if (!((unsigned long)block & (PAGE_SIZE-1))) {
spin_lock_irqsave(&block_lock, flags);
for (bb = bigblocks; bb; bb = bb->next)
if (bb->pages == block) {
spin_unlock_irqrestore(&slob_lock, flags);
return PAGE_SIZE << bb->order;
}
spin_unlock_irqrestore(&block_lock, flags);
}
return ((slob_t *)block - 1)->units * SLOB_UNIT;
}
struct kmem_cache {
unsigned int size, align;
const char *name;
void (*ctor)(void *, struct kmem_cache *, unsigned long);
void (*dtor)(void *, struct kmem_cache *, unsigned long);
};
struct kmem_cache *kmem_cache_create(const char *name, size_t size,
size_t align, unsigned long flags,
void (*ctor)(void*, struct kmem_cache *, unsigned long),
void (*dtor)(void*, struct kmem_cache *, unsigned long))
{
struct kmem_cache *c;
c = slob_alloc(sizeof(struct kmem_cache), flags, 0);
if (c) {
c->name = name;
c->size = size;
c->ctor = ctor;
c->dtor = dtor;
/* ignore alignment unless it's forced */
c->align = (flags & SLAB_MUST_HWCACHE_ALIGN) ? SLOB_ALIGN : 0;
if (c->align < align)
c->align = align;
}
return c;
}
EXPORT_SYMBOL(kmem_cache_create);
void kmem_cache_destroy(struct kmem_cache *c)
{
slob_free(c, sizeof(struct kmem_cache));
}
EXPORT_SYMBOL(kmem_cache_destroy);
void *kmem_cache_alloc(struct kmem_cache *c, gfp_t flags)
{
void *b;
if (c->size < PAGE_SIZE)
b = slob_alloc(c->size, flags, c->align);
else
b = (void *)__get_free_pages(flags, find_order(c->size));
if (c->ctor)
c->ctor(b, c, SLAB_CTOR_CONSTRUCTOR);
return b;
}
EXPORT_SYMBOL(kmem_cache_alloc);
void *kmem_cache_zalloc(struct kmem_cache *c, gfp_t flags)
{
void *ret = kmem_cache_alloc(c, flags);
if (ret)
memset(ret, 0, c->size);
return ret;
}
EXPORT_SYMBOL(kmem_cache_zalloc);
void kmem_cache_free(struct kmem_cache *c, void *b)
{
if (c->dtor)
c->dtor(b, c, 0);
if (c->size < PAGE_SIZE)
slob_free(b, c->size);
else
free_pages((unsigned long)b, find_order(c->size));
}
EXPORT_SYMBOL(kmem_cache_free);
unsigned int kmem_cache_size(struct kmem_cache *c)
{
return c->size;
}
EXPORT_SYMBOL(kmem_cache_size);
const char *kmem_cache_name(struct kmem_cache *c)
{
return c->name;
}
EXPORT_SYMBOL(kmem_cache_name);
static struct timer_list slob_timer = TIMER_INITIALIZER(
(void (*)(unsigned long))slob_timer_cbk, 0, 0);
int kmem_cache_shrink(struct kmem_cache *d)
{
return 0;
}
EXPORT_SYMBOL(kmem_cache_shrink);
int kmem_ptr_validate(struct kmem_cache *a, const void *b)
{
return 0;
}
void __init kmem_cache_init(void)
{
slob_timer_cbk();
}
static void slob_timer_cbk(void)
{
void *p = slob_alloc(PAGE_SIZE, 0, PAGE_SIZE-1);
if (p)
free_page((unsigned long)p);
mod_timer(&slob_timer, jiffies + HZ);
}
