*
* 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.
+ * allocator is 4 bytes on 32-bit and 8 bytes on 64-bit, though it
+ * could be as low as 2 if the compiler alignment requirements allow.
+ *
+ * The slob heap is a linked list of pages from __get_free_page, and
+ * within each page, there is a singly-linked list of free blocks (slob_t).
+ * The heap is 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.
+ * from kmalloc are 4-byte aligned and prepended with a 4-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_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.
+ * destructors for every SLAB allocation. Objects are returned with the
+ * 4-byte alignment unless the SLAB_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/kernel.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/cache.h>
#include <linux/init.h>
#include <linux/module.h>
-#include <linux/timer.h>
#include <linux/rcupdate.h>
+#include <linux/list.h>
+#include <asm/atomic.h>
+
+/* SLOB_MIN_ALIGN == sizeof(long) */
+#if BITS_PER_BYTE == 32
+#define SLOB_MIN_ALIGN 4
+#else
+#define SLOB_MIN_ALIGN 8
+#endif
+/*
+ * slob_block has a field 'units', which indicates size of block if +ve,
+ * or offset of next block if -ve (in SLOB_UNITs).
+ *
+ * Free blocks of size 1 unit simply contain the offset of the next block.
+ * Those with larger size contain their size in the first SLOB_UNIT of
+ * memory, and the offset of the next free block in the second SLOB_UNIT.
+ */
+#if PAGE_SIZE <= (32767 * SLOB_MIN_ALIGN)
+typedef s16 slobidx_t;
+#else
+typedef s32 slobidx_t;
+#endif
+
+/*
+ * Align struct slob_block to long for now, but can some embedded
+ * architectures get away with less?
+ */
struct slob_block {
- int units;
- struct slob_block *next;
-};
+ slobidx_t units;
+} __attribute__((aligned(SLOB_MIN_ALIGN)));
typedef struct slob_block slob_t;
+/*
+ * We use struct page fields to manage some slob allocation aspects,
+ * however to avoid the horrible mess in include/linux/mm_types.h, we'll
+ * just define our own struct page type variant here.
+ */
+struct slob_page {
+ union {
+ struct {
+ unsigned long flags; /* mandatory */
+ atomic_t _count; /* mandatory */
+ slobidx_t units; /* free units left in page */
+ unsigned long pad[2];
+ slob_t *free; /* first free slob_t in page */
+ struct list_head list; /* linked list of free pages */
+ };
+ struct page page;
+ };
+};
+static inline void struct_slob_page_wrong_size(void)
+{ BUILD_BUG_ON(sizeof(struct slob_page) != sizeof(struct page)); }
+
+/*
+ * free_slob_page: call before a slob_page is returned to the page allocator.
+ */
+static inline void free_slob_page(struct slob_page *sp)
+{
+ reset_page_mapcount(&sp->page);
+ sp->page.mapping = NULL;
+}
+
+/*
+ * All (partially) free slob pages go on this list.
+ */
+static LIST_HEAD(free_slob_pages);
+
+/*
+ * slob_page: True for all slob pages (false for bigblock pages)
+ */
+static inline int slob_page(struct slob_page *sp)
+{
+ return test_bit(PG_active, &sp->flags);
+}
+
+static inline void set_slob_page(struct slob_page *sp)
+{
+ __set_bit(PG_active, &sp->flags);
+}
+
+static inline void clear_slob_page(struct slob_page *sp)
+{
+ __clear_bit(PG_active, &sp->flags);
+}
+
+/*
+ * slob_page_free: true for pages on free_slob_pages list.
+ */
+static inline int slob_page_free(struct slob_page *sp)
+{
+ return test_bit(PG_private, &sp->flags);
+}
+
+static inline void set_slob_page_free(struct slob_page *sp)
+{
+ list_add(&sp->list, &free_slob_pages);
+ __set_bit(PG_private, &sp->flags);
+}
+
+static inline void clear_slob_page_free(struct slob_page *sp)
+{
+ list_del(&sp->list);
+ __clear_bit(PG_private, &sp->flags);
+}
+
#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;
-
/*
* struct slob_rcu is inserted at the tail of allocated slob blocks, which
* were created with a SLAB_DESTROY_BY_RCU slab. slob_rcu is used to free
int size;
};
-static slob_t arena = { .next = &arena, .units = 1 };
-static slob_t *slobfree = &arena;
-static bigblock_t *bigblocks;
+/*
+ * slob_lock protects all slob allocator structures.
+ */
static DEFINE_SPINLOCK(slob_lock);
-static DEFINE_SPINLOCK(block_lock);
-static void slob_free(void *b, int size);
-static void slob_timer_cbk(void);
+/*
+ * Encode the given size and next info into a free slob block s.
+ */
+static void set_slob(slob_t *s, slobidx_t size, slob_t *next)
+{
+ slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
+ slobidx_t offset = next - base;
+ if (size > 1) {
+ s[0].units = size;
+ s[1].units = offset;
+ } else
+ s[0].units = -offset;
+}
-static void *slob_alloc(size_t size, gfp_t gfp, int align)
+/*
+ * Return the size of a slob block.
+ */
+static slobidx_t slob_units(slob_t *s)
+{
+ if (s->units > 0)
+ return s->units;
+ return 1;
+}
+
+/*
+ * Return the next free slob block pointer after this one.
+ */
+static slob_t *slob_next(slob_t *s)
+{
+ slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
+ slobidx_t next;
+
+ if (s[0].units < 0)
+ next = -s[0].units;
+ else
+ next = s[1].units;
+ return base+next;
+}
+
+/*
+ * Returns true if s is the last free block in its page.
+ */
+static int slob_last(slob_t *s)
+{
+ return !((unsigned long)slob_next(s) & ~PAGE_MASK);
+}
+
+/*
+ * Allocate a slob block within a given slob_page sp.
+ */
+static void *slob_page_alloc(struct slob_page *sp, size_t size, 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) {
+ for (prev = NULL, cur = sp->free; ; prev = cur, cur = slob_next(cur)) {
+ slobidx_t avail = slob_units(cur);
+
if (align) {
aligned = (slob_t *)ALIGN((unsigned long)cur, align);
delta = aligned - cur;
}
- if (cur->units >= units + delta) { /* room enough? */
+ if (avail >= units + delta) { /* room enough? */
+ slob_t *next;
+
if (delta) { /* need to fragment head to align? */
- aligned->units = cur->units - delta;
- aligned->next = cur->next;
- cur->next = aligned;
- cur->units = delta;
+ next = slob_next(cur);
+ set_slob(aligned, avail - delta, next);
+ set_slob(cur, delta, aligned);
prev = cur;
cur = aligned;
+ avail = slob_units(cur);
}
- 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;
+ next = slob_next(cur);
+ if (avail == units) { /* exact fit? unlink. */
+ if (prev)
+ set_slob(prev, slob_units(prev), next);
+ else
+ sp->free = next;
+ } else { /* fragment */
+ if (prev)
+ set_slob(prev, slob_units(prev), cur + units);
+ else
+ sp->free = cur + units;
+ set_slob(cur + units, avail - units, next);
}
- slobfree = prev;
- spin_unlock_irqrestore(&slob_lock, flags);
+ sp->units -= units;
+ if (!sp->units)
+ clear_slob_page_free(sp);
return cur;
}
- if (cur == slobfree) {
- spin_unlock_irqrestore(&slob_lock, flags);
-
- if (size == PAGE_SIZE) /* trying to shrink arena? */
- return 0;
+ if (slob_last(cur))
+ return NULL;
+ }
+}
- cur = (slob_t *)__get_free_page(gfp);
- if (!cur)
- return 0;
+/*
+ * slob_alloc: entry point into the slob allocator.
+ */
+static void *slob_alloc(size_t size, gfp_t gfp, int align)
+{
+ struct slob_page *sp;
+ slob_t *b = NULL;
+ unsigned long flags;
- slob_free(cur, PAGE_SIZE);
- spin_lock_irqsave(&slob_lock, flags);
- cur = slobfree;
+ spin_lock_irqsave(&slob_lock, flags);
+ /* Iterate through each partially free page, try to find room */
+ list_for_each_entry(sp, &free_slob_pages, list) {
+ if (sp->units >= SLOB_UNITS(size)) {
+ b = slob_page_alloc(sp, size, align);
+ if (b)
+ break;
}
}
+ spin_unlock_irqrestore(&slob_lock, flags);
+
+ /* Not enough space: must allocate a new page */
+ if (!b) {
+ b = (slob_t *)__get_free_page(gfp);
+ if (!b)
+ return 0;
+ sp = (struct slob_page *)virt_to_page(b);
+ set_slob_page(sp);
+
+ spin_lock_irqsave(&slob_lock, flags);
+ sp->units = SLOB_UNITS(PAGE_SIZE);
+ sp->free = b;
+ INIT_LIST_HEAD(&sp->list);
+ set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE));
+ set_slob_page_free(sp);
+ b = slob_page_alloc(sp, size, align);
+ BUG_ON(!b);
+ spin_unlock_irqrestore(&slob_lock, flags);
+ }
+ return b;
}
+/*
+ * slob_free: entry point into the slob allocator.
+ */
static void slob_free(void *block, int size)
{
- slob_t *cur, *b = (slob_t *)block;
+ struct slob_page *sp;
+ slob_t *prev, *next, *b = (slob_t *)block;
+ slobidx_t units;
unsigned long flags;
if (!block)
return;
+ BUG_ON(!size);
- if (size)
- b->units = SLOB_UNITS(size);
+ sp = (struct slob_page *)virt_to_page(block);
+ 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 (sp->units + units == SLOB_UNITS(PAGE_SIZE)) {
+ /* Go directly to page allocator. Do not pass slob allocator */
+ if (slob_page_free(sp))
+ clear_slob_page_free(sp);
+ clear_slob_page(sp);
+ free_slob_page(sp);
+ free_page((unsigned long)b);
+ goto out;
+ }
- if (cur + cur->units == b) {
- cur->units += b->units;
- cur->next = b->next;
- } else
- cur->next = b;
+ if (!slob_page_free(sp)) {
+ /* This slob page is about to become partially free. Easy! */
+ sp->units = units;
+ sp->free = b;
+ set_slob(b, units,
+ (void *)((unsigned long)(b +
+ SLOB_UNITS(PAGE_SIZE)) & PAGE_MASK));
+ set_slob_page_free(sp);
+ goto out;
+ }
+
+ /*
+ * Otherwise the page is already partially free, so find reinsertion
+ * point.
+ */
+ sp->units += units;
- slobfree = cur;
+ if (b < sp->free) {
+ set_slob(b, units, sp->free);
+ sp->free = b;
+ } else {
+ prev = sp->free;
+ next = slob_next(prev);
+ while (b > next) {
+ prev = next;
+ next = slob_next(prev);
+ }
+ if (!slob_last(prev) && b + units == next) {
+ units += slob_units(next);
+ set_slob(b, units, slob_next(next));
+ } else
+ set_slob(b, units, next);
+
+ if (prev + slob_units(prev) == b) {
+ units = slob_units(b) + slob_units(prev);
+ set_slob(prev, units, slob_next(b));
+ } else
+ set_slob(prev, slob_units(prev), b);
+ }
+out:
spin_unlock_irqrestore(&slob_lock, flags);
}
+/*
+ * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend.
+ */
+
+struct bigblock {
+ int order;
+ void *pages;
+ struct bigblock *next;
+};
+typedef struct bigblock bigblock_t;
+
+static bigblock_t *bigblocks;
+
+static DEFINE_SPINLOCK(block_lock);
+
+
void *__kmalloc(size_t size, gfp_t gfp)
{
slob_t *m;
if (size < PAGE_SIZE - SLOB_UNIT) {
m = slob_alloc(size + SLOB_UNIT, gfp, 0);
- return m ? (void *)(m + 1) : 0;
+ if (m)
+ m->units = size;
+ return m+1;
}
bb = slob_alloc(sizeof(bigblock_t), gfp, 0);
void kfree(const void *block)
{
+ struct slob_page *sp;
+ slob_t *m;
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 */
+ sp = (struct slob_page *)virt_to_page(block);
+ if (!slob_page(sp)) {
+ /* 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) {
}
}
spin_unlock_irqrestore(&block_lock, flags);
+ WARN_ON(1);
+ return;
}
- slob_free((slob_t *)block - 1, 0);
+ m = (slob_t *)block - 1;
+ slob_free(m, m->units + SLOB_UNIT);
return;
}
size_t ksize(const void *block)
{
+ struct slob_page *sp;
bigblock_t *bb;
unsigned long flags;
if (!block)
return 0;
- if (!((unsigned long)block & (PAGE_SIZE-1))) {
+ sp = (struct slob_page *)virt_to_page(block);
+ if (!slob_page(sp)) {
spin_lock_irqsave(&block_lock, flags);
for (bb = bigblocks; bb; bb = bb->next)
if (bb->pages == block) {
spin_unlock_irqrestore(&block_lock, flags);
}
- return ((slob_t *)block - 1)->units * SLOB_UNIT;
+ return ((slob_t *)block - 1)->units + SLOB_UNIT;
}
struct kmem_cache {
}
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;
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);
}
projects / linux-2.6 / commitdiff