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Diffstat (limited to 'mm/slob.c')
| -rw-r--r-- | mm/slob.c | 647 |
1 files changed, 647 insertions, 0 deletions
diff --git a/mm/slob.c b/mm/slob.c new file mode 100644 index 0000000..bf7e8fc --- /dev/null +++ b/mm/slob.c @@ -0,0 +1,647 @@ +/* + * SLOB Allocator: Simple List Of Blocks + * + * Matt Mackall <mpm@selenic.com> 12/30/03 + * + * NUMA support by Paul Mundt, 2007. + * + * 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 as little as 2 bytes, however typically most architectures + * will require 4 bytes on 32-bit and 8 bytes on 64-bit. + * + * The slob heap is a set of linked list of pages from alloc_pages(), + * and within each page, there is a singly-linked list of free blocks + * (slob_t). The heap is grown on demand. To reduce fragmentation, + * heap pages are segregated into three lists, with objects less than + * 256 bytes, objects less than 1024 bytes, and all other objects. + * + * Allocation from heap involves first searching for a page with + * sufficient free blocks (using a next-fit-like approach) followed by + * a first-fit scan of the page. Deallocation inserts objects back + * into the free list in address order, so this is effectively an + * address-ordered first fit. + * + * Above this is an implementation of kmalloc/kfree. Blocks returned + * from kmalloc are prepended with a 4-byte header with the kmalloc size. + * If kmalloc is asked for objects of PAGE_SIZE or larger, it calls + * alloc_pages() directly, allocating compound pages so the page order + * does not have to be separately tracked, and also stores the exact + * allocation size in page->private so that it can be used to accurately + * provide ksize(). These objects are detected in kfree() because slob_page() + * is false for them. + * + * SLAB is emulated on top of SLOB by simply calling constructors and + * 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 alloc_pages(). As SLAB objects know their size, no separate + * size bookkeeping is necessary and there is essentially no allocation + * space overhead, and compound pages aren't needed for multi-page + * allocations. + * + * NUMA support in SLOB is fairly simplistic, pushing most of the real + * logic down to the page allocator, and simply doing the node accounting + * on the upper levels. In the event that a node id is explicitly + * provided, alloc_pages_node() with the specified node id is used + * instead. The common case (or when the node id isn't explicitly provided) + * will default to the current node, as per numa_node_id(). + * + * Node aware pages are still inserted in to the global freelist, and + * these are scanned for by matching against the node id encoded in the + * page flags. As a result, block allocations that can be satisfied from + * the freelist will only be done so on pages residing on the same node, + * in order to prevent random node placement. + */ + +#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/rcupdate.h> +#include <linux/list.h> +#include <asm/atomic.h> + +/* + * 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 * 2) +typedef s16 slobidx_t; +#else +typedef s32 slobidx_t; +#endif + +struct slob_block { + slobidx_t units; +}; +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 these lists. + */ +#define SLOB_BREAK1 256 +#define SLOB_BREAK2 1024 +static LIST_HEAD(free_slob_small); +static LIST_HEAD(free_slob_medium); +static LIST_HEAD(free_slob_large); + +/* + * slob_page: True for all slob pages (false for bigblock pages) + */ +static inline int slob_page(struct slob_page *sp) +{ + return PageSlobPage((struct page *)sp); +} + +static inline void set_slob_page(struct slob_page *sp) +{ + __SetPageSlobPage((struct page *)sp); +} + +static inline void clear_slob_page(struct slob_page *sp) +{ + __ClearPageSlobPage((struct page *)sp); +} + +/* + * slob_page_free: true for pages on free_slob_pages list. + */ +static inline int slob_page_free(struct slob_page *sp) +{ + return PageSlobFree((struct page *)sp); +} + +static void set_slob_page_free(struct slob_page *sp, struct list_head *list) +{ + list_add(&sp->list, list); + __SetPageSlobFree((struct page *)sp); +} + +static inline void clear_slob_page_free(struct slob_page *sp) +{ + list_del(&sp->list); + __ClearPageSlobFree((struct page *)sp); +} + +#define SLOB_UNIT sizeof(slob_t) +#define SLOB_UNITS(size) (((size) + SLOB_UNIT - 1)/SLOB_UNIT) +#define SLOB_ALIGN L1_CACHE_BYTES + +/* + * 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 + * the block using call_rcu. + */ +struct slob_rcu { + struct rcu_head head; + int size; +}; + +/* + * slob_lock protects all slob allocator structures. + */ +static DEFINE_SPINLOCK(slob_lock); + +/* + * 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; +} + +/* + * 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); +} + +static void *slob_new_page(gfp_t gfp, int order, int node) +{ + void *page; + +#ifdef CONFIG_NUMA + if (node != -1) + page = alloc_pages_node(node, gfp, order); + else +#endif + page = alloc_pages(gfp, order); + + if (!page) + return NULL; + + return page_address(page); +} + +/* + * 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); + + 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 (avail >= units + delta) { /* room enough? */ + slob_t *next; + + if (delta) { /* need to fragment head to align? */ + next = slob_next(cur); + set_slob(aligned, avail - delta, next); + set_slob(cur, delta, aligned); + prev = cur; + cur = aligned; + avail = slob_units(cur); + } + + 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); + } + + sp->units -= units; + if (!sp->units) + clear_slob_page_free(sp); + return cur; + } + if (slob_last(cur)) + return NULL; + } +} + +/* + * slob_alloc: entry point into the slob allocator. + */ +static void *slob_alloc(size_t size, gfp_t gfp, int align, int node) +{ + struct slob_page *sp; + struct list_head *prev; + struct list_head *slob_list; + slob_t *b = NULL; + unsigned long flags; + + if (size < SLOB_BREAK1) + slob_list = &free_slob_small; + else if (size < SLOB_BREAK2) + slob_list = &free_slob_medium; + else + slob_list = &free_slob_large; + + spin_lock_irqsave(&slob_lock, flags); + /* Iterate through each partially free page, try to find room */ + list_for_each_entry(sp, slob_list, list) { +#ifdef CONFIG_NUMA + /* + * If there's a node specification, search for a partial + * page with a matching node id in the freelist. + */ + if (node != -1 && page_to_nid(&sp->page) != node) + continue; +#endif + /* Enough room on this page? */ + if (sp->units < SLOB_UNITS(size)) + continue; + + /* Attempt to alloc */ + prev = sp->list.prev; + b = slob_page_alloc(sp, size, align); + if (!b) + continue; + + /* Improve fragment distribution and reduce our average + * search time by starting our next search here. (see + * Knuth vol 1, sec 2.5, pg 449) */ + if (prev != slob_list->prev && + slob_list->next != prev->next) + list_move_tail(slob_list, prev->next); + break; + } + spin_unlock_irqrestore(&slob_lock, flags); + + /* Not enough space: must allocate a new page */ + if (!b) { + b = slob_new_page(gfp & ~__GFP_ZERO, 0, node); + 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, slob_list); + b = slob_page_alloc(sp, size, align); + BUG_ON(!b); + spin_unlock_irqrestore(&slob_lock, flags); + } + if (unlikely((gfp & __GFP_ZERO) && b)) + memset(b, 0, size); + return b; +} + +/* + * slob_free: entry point into the slob allocator. + */ +static void slob_free(void *block, int size) +{ + struct slob_page *sp; + slob_t *prev, *next, *b = (slob_t *)block; + slobidx_t units; + unsigned long flags; + + if (unlikely(ZERO_OR_NULL_PTR(block))) + return; + BUG_ON(!size); + + sp = (struct slob_page *)virt_to_page(block); + units = SLOB_UNITS(size); + + spin_lock_irqsave(&slob_lock, flags); + + 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 (!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, &free_slob_small); + goto out; + } + + /* + * Otherwise the page is already partially free, so find reinsertion + * point. + */ + sp->units += units; + + if (b < sp->free) { + if (b + units == sp->free) { + units += slob_units(sp->free); + sp->free = slob_next(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. + */ + +#ifndef ARCH_KMALLOC_MINALIGN +#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long) +#endif + +#ifndef ARCH_SLAB_MINALIGN +#define ARCH_SLAB_MINALIGN __alignof__(unsigned long) +#endif + +void *__kmalloc_node(size_t size, gfp_t gfp, int node) +{ + unsigned int *m; + int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN); + + if (size < PAGE_SIZE - align) { + if (!size) + return ZERO_SIZE_PTR; + + m = slob_alloc(size + align, gfp, align, node); + if (!m) + return NULL; + *m = size; + return (void *)m + align; + } else { + void *ret; + + ret = slob_new_page(gfp | __GFP_COMP, get_order(size), node); + if (ret) { + struct page *page; + page = virt_to_page(ret); + page->private = size; + } + return ret; + } +} +EXPORT_SYMBOL(__kmalloc_node); + +void kfree(const void *block) +{ + struct slob_page *sp; + + if (unlikely(ZERO_OR_NULL_PTR(block))) + return; + + sp = (struct slob_page *)virt_to_page(block); + if (slob_page(sp)) { + int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN); + unsigned int *m = (unsigned int *)(block - align); + slob_free(m, *m + align); + } else + put_page(&sp->page); +} +EXPORT_SYMBOL(kfree); + +/* can't use ksize for kmem_cache_alloc memory, only kmalloc */ +size_t ksize(const void *block) +{ + struct slob_page *sp; + + BUG_ON(!block); + if (unlikely(block == ZERO_SIZE_PTR)) + return 0; + + sp = (struct slob_page *)virt_to_page(block); + if (slob_page(sp)) { + int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN); + unsigned int *m = (unsigned int *)(block - align); + return SLOB_UNITS(*m) * SLOB_UNIT; + } else + return sp->page.private; +} + +struct kmem_cache { + unsigned int size, align; + unsigned long flags; + const char *name; + void (*ctor)(void *); +}; + +struct kmem_cache *kmem_cache_create(const char *name, size_t size, + size_t align, unsigned long flags, void (*ctor)(void *)) +{ + struct kmem_cache *c; + + c = slob_alloc(sizeof(struct kmem_cache), + GFP_KERNEL, ARCH_KMALLOC_MINALIGN, -1); + + if (c) { + c->name = name; + c->size = size; + if (flags & SLAB_DESTROY_BY_RCU) { + /* leave room for rcu footer at the end of object */ + c->size += sizeof(struct slob_rcu); + } + c->flags = flags; + c->ctor = ctor; + /* ignore alignment unless it's forced */ + c->align = (flags & SLAB_HWCACHE_ALIGN) ? SLOB_ALIGN : 0; + if (c->align < ARCH_SLAB_MINALIGN) + c->align = ARCH_SLAB_MINALIGN; + if (c->align < align) + c->align = align; + } else if (flags & SLAB_PANIC) + panic("Cannot create slab cache %s\n", name); + + 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_node(struct kmem_cache *c, gfp_t flags, int node) +{ + void *b; + + if (c->size < PAGE_SIZE) + b = slob_alloc(c->size, flags, c->align, node); + else + b = slob_new_page(flags, get_order(c->size), node); + + if (c->ctor) + c->ctor(b); + + return b; +} +EXPORT_SYMBOL(kmem_cache_alloc_node); + +static void __kmem_cache_free(void *b, int size) +{ + if (size < PAGE_SIZE) + slob_free(b, size); + else + free_pages((unsigned long)b, get_order(size)); +} + +static void kmem_rcu_free(struct rcu_head *head) +{ + struct slob_rcu *slob_rcu = (struct slob_rcu *)head; + void *b = (void *)slob_rcu - (slob_rcu->size - sizeof(struct slob_rcu)); + + __kmem_cache_free(b, slob_rcu->size); +} + +void kmem_cache_free(struct kmem_cache *c, void *b) +{ + if (unlikely(c->flags & SLAB_DESTROY_BY_RCU)) { + struct slob_rcu *slob_rcu; + slob_rcu = b + (c->size - sizeof(struct slob_rcu)); + INIT_RCU_HEAD(&slob_rcu->head); + slob_rcu->size = c->size; + call_rcu(&slob_rcu->head, kmem_rcu_free); + } else { + __kmem_cache_free(b, 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); + +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; +} + +static unsigned int slob_ready __read_mostly; + +int slab_is_available(void) +{ + return slob_ready; +} + +void __init kmem_cache_init(void) +{ + slob_ready = 1; +} |
