Remove the core slob allocator's minimum alignment restrictions, and instead introduce the alignment restrictions at the slab API layer. This lets us heed the ARCH_KMALLOC/SLAB_MINALIGN directives, and also use __alignof__ (unsigned long) for the default alignment (which should allow relaxed alignment architectures to take better advantage of SLOB's small minimum alignment). Signed-off-by: Nick Piggin <npiggin@suse.de> Acked-by: Matt Mackall <mpm@selenic.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
602 lines
14 KiB
C
602 lines
14 KiB
C
/*
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* SLOB Allocator: Simple List Of Blocks
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*
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* Matt Mackall <mpm@selenic.com> 12/30/03
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*
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* How SLOB works:
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*
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* The core of SLOB is a traditional K&R style heap allocator, with
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* support for returning aligned objects. The granularity of this
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* allocator is as little as 2 bytes, however typically most architectures
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* will require 4 bytes on 32-bit and 8 bytes on 64-bit.
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*
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* The slob heap is a linked list of pages from __get_free_page, and
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* within each page, there is a singly-linked list of free blocks (slob_t).
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* The heap is grown on demand and allocation from the heap is currently
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* first-fit.
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*
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* Above this is an implementation of kmalloc/kfree. Blocks returned
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* from kmalloc are prepended with a 4-byte header with the kmalloc size.
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* If kmalloc is asked for objects of PAGE_SIZE or larger, it calls
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* __get_free_pages directly, allocating compound pages so the page order
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* does not have to be separately tracked, and also stores the exact
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* allocation size in page->private so that it can be used to accurately
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* provide ksize(). These objects are detected in kfree() because slob_page()
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* is false for them.
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*
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* SLAB is emulated on top of SLOB by simply calling constructors and
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* destructors for every SLAB allocation. Objects are returned with the
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* 4-byte alignment unless the SLAB_HWCACHE_ALIGN flag is set, in which
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* case the low-level allocator will fragment blocks to create the proper
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* alignment. Again, objects of page-size or greater are allocated by
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* calling __get_free_pages. As SLAB objects know their size, no separate
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* size bookkeeping is necessary and there is essentially no allocation
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* space overhead, and compound pages aren't needed for multi-page
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* allocations.
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*/
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/mm.h>
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#include <linux/cache.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/rcupdate.h>
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#include <linux/list.h>
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#include <asm/atomic.h>
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/*
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* slob_block has a field 'units', which indicates size of block if +ve,
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* or offset of next block if -ve (in SLOB_UNITs).
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*
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* Free blocks of size 1 unit simply contain the offset of the next block.
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* Those with larger size contain their size in the first SLOB_UNIT of
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* memory, and the offset of the next free block in the second SLOB_UNIT.
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*/
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#if PAGE_SIZE <= (32767 * 2)
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typedef s16 slobidx_t;
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#else
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typedef s32 slobidx_t;
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#endif
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struct slob_block {
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slobidx_t units;
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};
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typedef struct slob_block slob_t;
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/*
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* We use struct page fields to manage some slob allocation aspects,
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* however to avoid the horrible mess in include/linux/mm_types.h, we'll
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* just define our own struct page type variant here.
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*/
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struct slob_page {
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union {
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struct {
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unsigned long flags; /* mandatory */
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atomic_t _count; /* mandatory */
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slobidx_t units; /* free units left in page */
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unsigned long pad[2];
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slob_t *free; /* first free slob_t in page */
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struct list_head list; /* linked list of free pages */
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};
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struct page page;
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};
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};
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static inline void struct_slob_page_wrong_size(void)
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{ BUILD_BUG_ON(sizeof(struct slob_page) != sizeof(struct page)); }
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/*
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* free_slob_page: call before a slob_page is returned to the page allocator.
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*/
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static inline void free_slob_page(struct slob_page *sp)
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{
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reset_page_mapcount(&sp->page);
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sp->page.mapping = NULL;
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}
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/*
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* All (partially) free slob pages go on this list.
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*/
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static LIST_HEAD(free_slob_pages);
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/*
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* slob_page: True for all slob pages (false for bigblock pages)
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*/
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static inline int slob_page(struct slob_page *sp)
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{
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return test_bit(PG_active, &sp->flags);
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}
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static inline void set_slob_page(struct slob_page *sp)
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{
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__set_bit(PG_active, &sp->flags);
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}
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static inline void clear_slob_page(struct slob_page *sp)
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{
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__clear_bit(PG_active, &sp->flags);
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}
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/*
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* slob_page_free: true for pages on free_slob_pages list.
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*/
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static inline int slob_page_free(struct slob_page *sp)
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{
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return test_bit(PG_private, &sp->flags);
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}
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static inline void set_slob_page_free(struct slob_page *sp)
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{
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list_add(&sp->list, &free_slob_pages);
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__set_bit(PG_private, &sp->flags);
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}
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static inline void clear_slob_page_free(struct slob_page *sp)
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{
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list_del(&sp->list);
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__clear_bit(PG_private, &sp->flags);
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}
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#define SLOB_UNIT sizeof(slob_t)
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#define SLOB_UNITS(size) (((size) + SLOB_UNIT - 1)/SLOB_UNIT)
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#define SLOB_ALIGN L1_CACHE_BYTES
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/*
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* struct slob_rcu is inserted at the tail of allocated slob blocks, which
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* were created with a SLAB_DESTROY_BY_RCU slab. slob_rcu is used to free
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* the block using call_rcu.
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*/
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struct slob_rcu {
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struct rcu_head head;
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int size;
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};
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/*
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* slob_lock protects all slob allocator structures.
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*/
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static DEFINE_SPINLOCK(slob_lock);
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/*
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* Encode the given size and next info into a free slob block s.
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*/
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static void set_slob(slob_t *s, slobidx_t size, slob_t *next)
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{
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slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
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slobidx_t offset = next - base;
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if (size > 1) {
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s[0].units = size;
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s[1].units = offset;
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} else
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s[0].units = -offset;
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}
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/*
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* Return the size of a slob block.
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*/
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static slobidx_t slob_units(slob_t *s)
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{
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if (s->units > 0)
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return s->units;
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return 1;
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}
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/*
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* Return the next free slob block pointer after this one.
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*/
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static slob_t *slob_next(slob_t *s)
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{
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slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
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slobidx_t next;
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if (s[0].units < 0)
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next = -s[0].units;
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else
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next = s[1].units;
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return base+next;
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}
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/*
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* Returns true if s is the last free block in its page.
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*/
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static int slob_last(slob_t *s)
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{
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return !((unsigned long)slob_next(s) & ~PAGE_MASK);
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}
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/*
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* Allocate a slob block within a given slob_page sp.
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*/
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static void *slob_page_alloc(struct slob_page *sp, size_t size, int align)
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{
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slob_t *prev, *cur, *aligned = 0;
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int delta = 0, units = SLOB_UNITS(size);
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for (prev = NULL, cur = sp->free; ; prev = cur, cur = slob_next(cur)) {
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slobidx_t avail = slob_units(cur);
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if (align) {
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aligned = (slob_t *)ALIGN((unsigned long)cur, align);
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delta = aligned - cur;
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}
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if (avail >= units + delta) { /* room enough? */
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slob_t *next;
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if (delta) { /* need to fragment head to align? */
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next = slob_next(cur);
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set_slob(aligned, avail - delta, next);
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set_slob(cur, delta, aligned);
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prev = cur;
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cur = aligned;
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avail = slob_units(cur);
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}
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next = slob_next(cur);
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if (avail == units) { /* exact fit? unlink. */
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if (prev)
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set_slob(prev, slob_units(prev), next);
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else
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sp->free = next;
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} else { /* fragment */
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if (prev)
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set_slob(prev, slob_units(prev), cur + units);
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else
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sp->free = cur + units;
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set_slob(cur + units, avail - units, next);
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}
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sp->units -= units;
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if (!sp->units)
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clear_slob_page_free(sp);
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return cur;
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}
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if (slob_last(cur))
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return NULL;
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}
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}
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/*
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* slob_alloc: entry point into the slob allocator.
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*/
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static void *slob_alloc(size_t size, gfp_t gfp, int align)
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{
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struct slob_page *sp;
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slob_t *b = NULL;
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unsigned long flags;
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spin_lock_irqsave(&slob_lock, flags);
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/* Iterate through each partially free page, try to find room */
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list_for_each_entry(sp, &free_slob_pages, list) {
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if (sp->units >= SLOB_UNITS(size)) {
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b = slob_page_alloc(sp, size, align);
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if (b)
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break;
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}
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}
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spin_unlock_irqrestore(&slob_lock, flags);
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/* Not enough space: must allocate a new page */
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if (!b) {
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b = (slob_t *)__get_free_page(gfp);
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if (!b)
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return 0;
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sp = (struct slob_page *)virt_to_page(b);
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set_slob_page(sp);
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spin_lock_irqsave(&slob_lock, flags);
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sp->units = SLOB_UNITS(PAGE_SIZE);
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sp->free = b;
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INIT_LIST_HEAD(&sp->list);
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set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE));
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set_slob_page_free(sp);
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b = slob_page_alloc(sp, size, align);
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BUG_ON(!b);
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spin_unlock_irqrestore(&slob_lock, flags);
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}
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return b;
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}
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/*
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* slob_free: entry point into the slob allocator.
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*/
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static void slob_free(void *block, int size)
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{
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struct slob_page *sp;
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slob_t *prev, *next, *b = (slob_t *)block;
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slobidx_t units;
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unsigned long flags;
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if (!block)
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return;
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BUG_ON(!size);
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sp = (struct slob_page *)virt_to_page(block);
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units = SLOB_UNITS(size);
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spin_lock_irqsave(&slob_lock, flags);
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if (sp->units + units == SLOB_UNITS(PAGE_SIZE)) {
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/* Go directly to page allocator. Do not pass slob allocator */
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if (slob_page_free(sp))
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clear_slob_page_free(sp);
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clear_slob_page(sp);
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free_slob_page(sp);
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free_page((unsigned long)b);
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goto out;
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}
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if (!slob_page_free(sp)) {
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/* This slob page is about to become partially free. Easy! */
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sp->units = units;
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sp->free = b;
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set_slob(b, units,
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(void *)((unsigned long)(b +
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SLOB_UNITS(PAGE_SIZE)) & PAGE_MASK));
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set_slob_page_free(sp);
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goto out;
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}
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/*
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* Otherwise the page is already partially free, so find reinsertion
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* point.
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*/
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sp->units += units;
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if (b < sp->free) {
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set_slob(b, units, sp->free);
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sp->free = b;
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} else {
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prev = sp->free;
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next = slob_next(prev);
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while (b > next) {
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prev = next;
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next = slob_next(prev);
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}
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if (!slob_last(prev) && b + units == next) {
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units += slob_units(next);
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set_slob(b, units, slob_next(next));
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} else
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set_slob(b, units, next);
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if (prev + slob_units(prev) == b) {
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units = slob_units(b) + slob_units(prev);
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set_slob(prev, units, slob_next(b));
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} else
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set_slob(prev, slob_units(prev), b);
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}
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out:
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spin_unlock_irqrestore(&slob_lock, flags);
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}
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/*
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* End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend.
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*/
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#ifndef ARCH_KMALLOC_MINALIGN
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#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long)
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#endif
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#ifndef ARCH_SLAB_MINALIGN
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#define ARCH_SLAB_MINALIGN __alignof__(unsigned long)
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#endif
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void *__kmalloc(size_t size, gfp_t gfp)
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{
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int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
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if (size < PAGE_SIZE - align) {
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unsigned int *m;
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m = slob_alloc(size + align, gfp, align);
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if (m)
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*m = size;
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return (void *)m + align;
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} else {
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void *ret;
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ret = (void *) __get_free_pages(gfp | __GFP_COMP,
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get_order(size));
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if (ret) {
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struct page *page;
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page = virt_to_page(ret);
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page->private = size;
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}
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return ret;
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}
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}
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EXPORT_SYMBOL(__kmalloc);
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/**
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* krealloc - reallocate memory. The contents will remain unchanged.
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*
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* @p: object to reallocate memory for.
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* @new_size: how many bytes of memory are required.
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* @flags: the type of memory to allocate.
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*
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* The contents of the object pointed to are preserved up to the
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* lesser of the new and old sizes. If @p is %NULL, krealloc()
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* behaves exactly like kmalloc(). If @size is 0 and @p is not a
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* %NULL pointer, the object pointed to is freed.
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*/
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void *krealloc(const void *p, size_t new_size, gfp_t flags)
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{
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void *ret;
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if (unlikely(!p))
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return kmalloc_track_caller(new_size, flags);
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if (unlikely(!new_size)) {
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kfree(p);
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return NULL;
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}
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ret = kmalloc_track_caller(new_size, flags);
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if (ret) {
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memcpy(ret, p, min(new_size, ksize(p)));
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kfree(p);
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}
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return ret;
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}
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EXPORT_SYMBOL(krealloc);
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void kfree(const void *block)
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{
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struct slob_page *sp;
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if (!block)
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return;
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sp = (struct slob_page *)virt_to_page(block);
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if (slob_page(sp)) {
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int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
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unsigned int *m = (unsigned int *)(block - align);
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slob_free(m, *m + align);
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} else
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put_page(&sp->page);
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}
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EXPORT_SYMBOL(kfree);
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/* can't use ksize for kmem_cache_alloc memory, only kmalloc */
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size_t ksize(const void *block)
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{
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struct slob_page *sp;
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if (!block)
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return 0;
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sp = (struct slob_page *)virt_to_page(block);
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if (slob_page(sp))
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return ((slob_t *)block - 1)->units + SLOB_UNIT;
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else
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return sp->page.private;
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}
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struct kmem_cache {
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unsigned int size, align;
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unsigned long flags;
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const char *name;
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void (*ctor)(void *, struct kmem_cache *, unsigned long);
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};
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struct kmem_cache *kmem_cache_create(const char *name, size_t size,
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size_t align, unsigned long flags,
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void (*ctor)(void*, struct kmem_cache *, unsigned long),
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void (*dtor)(void*, struct kmem_cache *, unsigned long))
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{
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struct kmem_cache *c;
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c = slob_alloc(sizeof(struct kmem_cache), flags, 0);
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if (c) {
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c->name = name;
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c->size = size;
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if (flags & SLAB_DESTROY_BY_RCU) {
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/* leave room for rcu footer at the end of object */
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c->size += sizeof(struct slob_rcu);
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}
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c->flags = flags;
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c->ctor = ctor;
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/* ignore alignment unless it's forced */
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c->align = (flags & SLAB_HWCACHE_ALIGN) ? SLOB_ALIGN : 0;
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if (c->align < ARCH_SLAB_MINALIGN)
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c->align = ARCH_SLAB_MINALIGN;
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if (c->align < align)
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c->align = align;
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} else if (flags & SLAB_PANIC)
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panic("Cannot create slab cache %s\n", name);
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return c;
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}
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EXPORT_SYMBOL(kmem_cache_create);
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void kmem_cache_destroy(struct kmem_cache *c)
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{
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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, get_order(c->size));
|
|
|
|
if (c->ctor)
|
|
c->ctor(b, c, 0);
|
|
|
|
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);
|
|
|
|
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;
|
|
}
|
|
|
|
void __init kmem_cache_init(void)
|
|
{
|
|
}
|