/*
?*?slab?allocator?implementation
?*
?*?A?slab?allocator?reserves?a?ZONE?for?each?chunk?size?then?lays?the
?*?chunks?out?in?an?array?within?the?zone.??Allocation?and?deallocation
?*?is?nearly?instantanious?and?fragmentation/overhead?losses?are?limited
?*?to?a?fixed?worst-case?amount.
?*
?*?The?downside?of?this?slab?implementation?is?in?the?chunk?size
?*?multiplied?by?the?number?of?zones.??~80?zones?*?128K?=?10MB?of?VM?per?cpu.
?*?In?a?kernel?implementation?all?this?memory?will?be?physical?so
?*?the?zone?size?is?adjusted?downward?on?machines?with?less?physical
?*?memory.??The?upside?is?that?overhead?is?bounded...?this?is?the?*worst*
?*?case?overhead.
?*
?*?Slab?management?is?done?on?a?per-cpu?basis?and?no?locking?or?mutexes
?*?are?required?only?a?critical?section.??When?one?cpu?frees?memory
?*?belonging?to?another?cpu‘s?slab?manager?an?asynchronous?IPI?message
?*?will?be?queued?to?execute?the?operation.???In?addition?both?the
?*?high?level?slab?allocator?and?the?low?level?zone?allocator?optimize
?*?M_ZERO?requests?and?the?slab?allocator?does?not?have?to?pre?initialize
?*?the?linked?list?of?chunks.
?*
?*?XXX?Balancing?is?needed?between?cpus.??Balance?will?be?handled?through
?*?asynchronous?IPIs?primarily?by?reassigning?the?z_Cpu?ownership?of?chunks.
?*
?*?XXX?If?we?have?to?allocate?a?new?zone?and?M_USE_RESERVE?is?set?use?of
?*?the?new?zone?should?be?restricted?to?M_USE_RESERVE?requests?only.
?*
?*	Alloc?Size	Chunking????????Number?of?zones
?*	0-127		8				16
?*	128-255		16				8
?*	256-511		32				8
?*	512-1023	64				8
?*	1024-2047	128				8
?*	2048-4095	256				8
?*	4096-8191	512				8
?*	8192-16383	1024			8
?*	16384-32767	2048			8
?*	（if?PAGE_SIZE?is?4K?the?maximum?zone?allocation?is?16383）
?*
?*	Allocations?>=?zone_limit?go?directly?to?kmem.
?*
?*			API?REQUIREMENTS?AND?SIDE?EFFECTS
?*
?*????To?operate?as?a?drop-in?replacement?to?the?FreeBSD-4.x?malloc（）?we
?*????have?remained?compatible?with?the?following?API?requirements:
?*
?*????+?small?power-of-2?sized?allocations?are?power-of-2?aligned?（kern_tty）
?*????+?all?power-of-2?sized?allocations?are?power-of-2?aligned?（twe）
?*????+?malloc（0）?is?allowed?and?returns?non-0?（ahc?driver）
?*????+?ability?to?allocate?arbitrarily?large?chunks?of?memory
?*/

/*
?*?Chunk?structure?for?free?elements
?*/


#define?ASSERT（a）
#define?ALIGN（size?align）			（（（size）?+?（align）?-?1）?&?~（（align）-1））
/**
?*?@ingroup?BasicDef
?*
?*?@def?ALIGN_DOWN（size?align）
?*?Return?the?down?number?of?aligned?at?specified?width.?ALIGN_DOWN（13?4）
?*?would?return?12.?
?*/
#define?ALIGN_DOWN（size?align）		（（size）?&?~（（align）?-1））?

#define?PAGE_SIZE					4096
#define?PAGE_MASK?				（PAGE_SIZE?-?1）
#define?PAGE_BITS					12
#define?SLAB_DEBUG
#define?MEM_STATS

/*?some?statistical?variable?*/
#ifdef?MEM_STATS
static?unsigned?int?used_mem?max_mem;
#endif
static?void?（*malloc_hook）（void?*ptr?unsigned?int?size）=NULL;
static?void?（*free_hook）（void?*ptr）=NULL;

void?malloc_sethook（void?（*hook）（void?*ptr?unsigned?int?size））
{
	malloc_hook?