static int init_bucket(Bucket * const bucket)
{
init_slab(&bucket->slab, sizeof(Slot), "slots");
bucket->bucket_size = (NbSlots) BUCKET_SIZE;
bucket->busy_slots = (NbSlots) 0U;
return 0;
}
static struct page *make_new_slab(struct kmem_cache *cache)
{
struct page *page = alloc_pages(cache->pages_per_slab);
if (page)
{
init_slab(page, cache);
}
return page;
}
/* Initialize a slab cache without any allocations */
void slab_cache_init(slab_cache_t *slab_cache, void *slab, size_t object_size, int flags)
{
/* Fill in the slab cache information */
slab_cache->object_size = object_size;
slab_cache->flags = flags;
slab_cache->empty = (slab_header_t*) slab;
slab_cache->partial = NULL;
slab_cache->full = NULL;
spinlock_recursive_init(&slab_cache->lock);
/* Calculate the amount of available space in the slab */
size_t available_space = SLAB_SIZE - sizeof(slab_header_t);
/* Find the largest number of objects we can pack into the slab */
size_t objs_per_slab = 0;
while (true)
{
/* Calculate the space needed for objects and bitmaps */
size_t object_space = (objs_per_slab + 1) * object_size;
size_t bitmap_space = ceil(objs_per_slab + 1, 8);
/* Adjust the bitmap space to a multiple of 4, if needed */
if (bitmap_space & 3)
{
bitmap_space = (bitmap_space & ~3) + 4;
}
/* If the needed space exceeds the available space, end the loop */
if (object_space + bitmap_space > available_space)
{
/* We can't put any objects in the slab */
if (objs_per_slab == 0) return;
/* Fill in the slab header size and number of objects per slab */
slab_cache->slab_header_size = sizeof(slab_header_t) + bitmap_space;
slab_cache->objs_per_slab = objs_per_slab;
/* Set up the slab's data */
init_slab(slab_cache, (slab_header_t*) slab, bitmap_space);
return;
}
/* We can fit one more object than our original guess */
objs_per_slab++;
}
}
/* Allocate an object from a slab cache */
void *slab_cache_alloc(slab_cache_t *slab_cache)
{
/* Lock the entire slab cache */
spinlock_recursive_acquire(&slab_cache->lock);
/* Take a partial slab if possible, or an empty one if not */
find_slab: ;
slab_header_t *slab_header = NULL;
if (slab_cache->partial)
{
/* Use the first partial slab we see */
slab_header = slab_cache->partial;
/* No objects left after allocation */
if (slab_header->num_free_objs == 1)
{
slab_header_t *old_full_head = slab_cache->full;
slab_cache->partial = slab_header->next;
slab_header->next = old_full_head;
slab_cache->full = slab_header;
}
}
/* Empty slab available */
else if (slab_cache->empty)
{
/* Use the first empty slab we see */
slab_header = slab_cache->empty;
/* No objects left after allocation, so put the slab in full */
if (slab_header->num_free_objs == 1)
{
slab_header_t *old_full_head = slab_cache->full;
slab_cache->empty = slab_header->next;
slab_header->next = old_full_head;
slab_cache->full = slab_header;
}
/* Otherwise, put it in the partial list */
else
{
slab_header_t *old_partial_head = slab_cache->partial;
slab_cache->empty = slab_header->next;
slab_header->next = old_partial_head;
slab_cache->partial = slab_header;
}
}
/* No empty or partial slabs available */
else
{
/* Allocate a new slab and fill in its information */
slab_header = (slab_header_t*) addrspace_alloc(ADDRSPACE_SYSTEM, SLAB_SIZE, SLAB_SIZE, slab_cache->flags | PAGE_GLOBAL);
if (!slab_header)
{
spinlock_recursive_release(&slab_cache->lock);
return NULL;
}
init_slab(slab_cache, slab_header, slab_cache->slab_header_size - sizeof(slab_header_t));
/* Add it to the empty list and redo this */
slab_header->next = slab_cache->empty;
slab_cache->empty = slab_header;
goto find_slab;
}
/* Now that we've found a slab, we can lock it and unlock the entire cache */
spinlock_recursive_acquire(&slab_header->lock);
spinlock_recursive_release(&slab_cache->lock);
/* One less object in the slab */
slab_header->num_free_objs--;
/* Search the bitmap for an available free object */
size_t bitmap_space = slab_cache->slab_header_size - sizeof(slab_header_t);
for (size_t i = 0; i < bitmap_space; i++)
{
uint8_t byte = slab_header->free_bitmap[i];
for (uint8_t j = 0; j < 8; j++)
{
if (byte == 0xFF)
{
break;
}
if (byte & 1)
{
byte >>= 1;
continue;
}
slab_header->free_bitmap[i] |= (1 << j);
size_t object_num = (i * 8) + j;
void *object = ((void*) slab_header) + slab_cache->slab_header_size + (object_num * slab_cache->object_size);
spinlock_recursive_release(&slab_header->lock);
return object;
}
}
