source: rtems-libbsd/freebsd/sys/vm/uma_int.h @ b68b88c

/*-
 * Copyright (c) 2002-2005, 2009 Jeffrey Roberson <jeff@FreeBSD.org>
 * Copyright (c) 2004, 2005 Bosko Milekic <bmilekic@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * $FreeBSD$
 *
 */

/* 
 * This file includes definitions, structures, prototypes, and inlines that
 * should not be used outside of the actual implementation of UMA.
 */

/* 
 * Here's a quick description of the relationship between the objects:
 *
 * Kegs contain lists of slabs which are stored in either the full bin, empty
 * bin, or partially allocated bin, to reduce fragmentation.  They also contain
 * the user supplied value for size, which is adjusted for alignment purposes
 * and rsize is the result of that.  The Keg also stores information for
 * managing a hash of page addresses that maps pages to uma_slab_t structures
 * for pages that don't have embedded uma_slab_t's.
 *  
 * The uma_slab_t may be embedded in a UMA_SLAB_SIZE chunk of memory or it may
 * be allocated off the page from a special slab zone.  The free list within a
 * slab is managed with a linked list of indices, which are 8 bit values.  If
 * UMA_SLAB_SIZE is defined to be too large I will have to switch to 16bit
 * values.  Currently on alpha you can get 250 or so 32 byte items and on x86
 * you can get 250 or so 16byte items.  For item sizes that would yield more
 * than 10% memory waste we potentially allocate a separate uma_slab_t if this
 * will improve the number of items per slab that will fit.  
 *
 * Other potential space optimizations are storing the 8bit of linkage in space
 * wasted between items due to alignment problems.  This may yield a much better
 * memory footprint for certain sizes of objects.  Another alternative is to
 * increase the UMA_SLAB_SIZE, or allow for dynamic slab sizes.  I prefer
 * dynamic slab sizes because we could stick with 8 bit indices and only use
 * large slab sizes for zones with a lot of waste per slab.  This may create
 * inefficiencies in the vm subsystem due to fragmentation in the address space.
 *
 * The only really gross cases, with regards to memory waste, are for those
 * items that are just over half the page size.   You can get nearly 50% waste,
 * so you fall back to the memory footprint of the power of two allocator. I
 * have looked at memory allocation sizes on many of the machines available to
 * me, and there does not seem to be an abundance of allocations at this range
 * so at this time it may not make sense to optimize for it.  This can, of 
 * course, be solved with dynamic slab sizes.
 *
 * Kegs may serve multiple Zones but by far most of the time they only serve
 * one.  When a Zone is created, a Keg is allocated and setup for it.  While
 * the backing Keg stores slabs, the Zone caches Buckets of items allocated
 * from the slabs.  Each Zone is equipped with an init/fini and ctor/dtor
 * pair, as well as with its own set of small per-CPU caches, layered above
 * the Zone's general Bucket cache.
 *
 * The PCPU caches are protected by critical sections, and may be accessed
 * safely only from their associated CPU, while the Zones backed by the same
 * Keg all share a common Keg lock (to coalesce contention on the backing
 * slabs).  The backing Keg typically only serves one Zone but in the case of
 * multiple Zones, one of the Zones is considered the Master Zone and all
 * Zone-related stats from the Keg are done in the Master Zone.  For an
 * example of a Multi-Zone setup, refer to the Mbuf allocation code.
 */

/*
 *      This is the representation for normal (Non OFFPAGE slab)
 *
 *      i == item
 *      s == slab pointer
 *
 *      <----------------  Page (UMA_SLAB_SIZE) ------------------>
 *      ___________________________________________________________
 *     | _  _  _  _  _  _  _  _  _  _  _  _  _  _  _   ___________ |
 *     ||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i| |slab header||
 *     ||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_| |___________|| 
 *     |___________________________________________________________|
 *
 *
 *      This is an OFFPAGE slab. These can be larger than UMA_SLAB_SIZE.
 *
 *      ___________________________________________________________
 *     | _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _   |
 *     ||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i|  |
 *     ||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_|  |
 *     |___________________________________________________________|
 *       ___________    ^
 *      |slab header|   |
 *      |___________|---*
 *
 */

#ifndef VM_UMA_INT_H
#define VM_UMA_INT_H

#define UMA_SLAB_SIZE   PAGE_SIZE       /* How big are our slabs? */
#define UMA_SLAB_MASK   (PAGE_SIZE - 1) /* Mask to get back to the page */
#define UMA_SLAB_SHIFT  PAGE_SHIFT      /* Number of bits PAGE_MASK */

#define UMA_BOOT_PAGES          64      /* Pages allocated for startup */

/* Max waste before going to off page slab management */
#define UMA_MAX_WASTE   (UMA_SLAB_SIZE / 10)

/*
 * I doubt there will be many cases where this is exceeded. This is the initial
 * size of the hash table for uma_slabs that are managed off page. This hash
 * does expand by powers of two.  Currently it doesn't get smaller.
 */
#define UMA_HASH_SIZE_INIT      32              

/* 
 * I should investigate other hashing algorithms.  This should yield a low
 * number of collisions if the pages are relatively contiguous.
 *
 * This is the same algorithm that most processor caches use.
 *
 * I'm shifting and masking instead of % because it should be faster.
 */

#define UMA_HASH(h, s) ((((unsigned long)s) >> UMA_SLAB_SHIFT) &        \
    (h)->uh_hashmask)

#define UMA_HASH_INSERT(h, s, mem)                                      \
                SLIST_INSERT_HEAD(&(h)->uh_slab_hash[UMA_HASH((h),      \
                    (mem))], (s), us_hlink)
#define UMA_HASH_REMOVE(h, s, mem)                                      \
                SLIST_REMOVE(&(h)->uh_slab_hash[UMA_HASH((h),           \
                    (mem))], (s), uma_slab, us_hlink)

/* Hash table for freed address -> slab translation */

SLIST_HEAD(slabhead, uma_slab);

struct uma_hash {
        struct slabhead *uh_slab_hash;  /* Hash table for slabs */
        int             uh_hashsize;    /* Current size of the hash table */
        int             uh_hashmask;    /* Mask used during hashing */
};

/*
 * align field or structure to cache line
 */
#if defined(__amd64__)
#define UMA_ALIGN       __aligned(CACHE_LINE_SIZE)
#else
#define UMA_ALIGN
#endif

/*
 * Structures for per cpu queues.
 */

struct uma_bucket {
        LIST_ENTRY(uma_bucket)  ub_link;        /* Link into the zone */
        int16_t ub_cnt;                         /* Count of free items. */
        int16_t ub_entries;                     /* Max items. */
        void    *ub_bucket[];                   /* actual allocation storage */
};

typedef struct uma_bucket * uma_bucket_t;

struct uma_cache {
        uma_bucket_t    uc_freebucket;  /* Bucket we're freeing to */
        uma_bucket_t    uc_allocbucket; /* Bucket to allocate from */
        u_int64_t       uc_allocs;      /* Count of allocations */
        u_int64_t       uc_frees;       /* Count of frees */
} UMA_ALIGN;

typedef struct uma_cache * uma_cache_t;

/*
 * Keg management structure
 *
 * TODO: Optimize for cache line size
 *
 */
struct uma_keg {
        LIST_ENTRY(uma_keg)     uk_link;        /* List of all kegs */

        struct mtx      uk_lock;        /* Lock for the keg */
        struct uma_hash uk_hash;

        const char      *uk_name;               /* Name of creating zone. */
        LIST_HEAD(,uma_zone)    uk_zones;       /* Keg's zones */
        LIST_HEAD(,uma_slab)    uk_part_slab;   /* partially allocated slabs */
        LIST_HEAD(,uma_slab)    uk_free_slab;   /* empty slab list */
        LIST_HEAD(,uma_slab)    uk_full_slab;   /* full slabs */

        u_int32_t       uk_recurse;     /* Allocation recursion count */
        u_int32_t       uk_align;       /* Alignment mask */
        u_int32_t       uk_pages;       /* Total page count */
        u_int32_t       uk_free;        /* Count of items free in slabs */
        u_int32_t       uk_size;        /* Requested size of each item */
        u_int32_t       uk_rsize;       /* Real size of each item */
        u_int32_t       uk_maxpages;    /* Maximum number of pages to alloc */

        uma_init        uk_init;        /* Keg's init routine */
        uma_fini        uk_fini;        /* Keg's fini routine */
        uma_alloc       uk_allocf;      /* Allocation function */
        uma_free        uk_freef;       /* Free routine */

        struct vm_object        *uk_obj;        /* Zone specific object */
        vm_offset_t     uk_kva;         /* Base kva for zones with objs */
        uma_zone_t      uk_slabzone;    /* Slab zone backing us, if OFFPAGE */

        u_int16_t       uk_pgoff;       /* Offset to uma_slab struct */
        u_int16_t       uk_ppera;       /* pages per allocation from backend */
        u_int16_t       uk_ipers;       /* Items per slab */
        u_int32_t       uk_flags;       /* Internal flags */
};
typedef struct uma_keg  * uma_keg_t;

/* Page management structure */

/* Sorry for the union, but space efficiency is important */
struct uma_slab_head {
        uma_keg_t       us_keg;                 /* Keg we live in */
        union {
                LIST_ENTRY(uma_slab)    _us_link;       /* slabs in zone */
                unsigned long   _us_size;       /* Size of allocation */
        } us_type;
        SLIST_ENTRY(uma_slab)   us_hlink;       /* Link for hash table */
        u_int8_t        *us_data;               /* First item */
        u_int8_t        us_flags;               /* Page flags see uma.h */
        u_int8_t        us_freecount;   /* How many are free? */
        u_int8_t        us_firstfree;   /* First free item index */
};

/* The standard slab structure */
struct uma_slab {
        struct uma_slab_head    us_head;        /* slab header data */
        struct {
                u_int8_t        us_item;
        } us_freelist[1];                       /* actual number bigger */
};

/*
 * The slab structure for UMA_ZONE_REFCNT zones for whose items we
 * maintain reference counters in the slab for.
 */
struct uma_slab_refcnt {
        struct uma_slab_head    us_head;        /* slab header data */
        struct {
                u_int8_t        us_item;
                u_int32_t       us_refcnt;
        } us_freelist[1];                       /* actual number bigger */
};

#define us_keg          us_head.us_keg
#define us_link         us_head.us_type._us_link
#define us_size         us_head.us_type._us_size
#define us_hlink        us_head.us_hlink
#define us_data         us_head.us_data
#define us_flags        us_head.us_flags
#define us_freecount    us_head.us_freecount
#define us_firstfree    us_head.us_firstfree

typedef struct uma_slab * uma_slab_t;
typedef struct uma_slab_refcnt * uma_slabrefcnt_t;
typedef uma_slab_t (*uma_slaballoc)(uma_zone_t, uma_keg_t, int);


/*
 * These give us the size of one free item reference within our corresponding
 * uma_slab structures, so that our calculations during zone setup are correct
 * regardless of what the compiler decides to do with padding the structure
 * arrays within uma_slab.
 */
#define UMA_FRITM_SZ    (sizeof(struct uma_slab) - sizeof(struct uma_slab_head))
#define UMA_FRITMREF_SZ (sizeof(struct uma_slab_refcnt) -       \
    sizeof(struct uma_slab_head))

struct uma_klink {
        LIST_ENTRY(uma_klink)   kl_link;
        uma_keg_t               kl_keg;
};
typedef struct uma_klink *uma_klink_t;

/*
 * Zone management structure 
 *
 * TODO: Optimize for cache line size
 *
 */
struct uma_zone {
        const char      *uz_name;       /* Text name of the zone */
        struct mtx      *uz_lock;       /* Lock for the zone (keg's lock) */

        LIST_ENTRY(uma_zone)    uz_link;        /* List of all zones in keg */
        LIST_HEAD(,uma_bucket)  uz_full_bucket; /* full buckets */
        LIST_HEAD(,uma_bucket)  uz_free_bucket; /* Buckets for frees */

        LIST_HEAD(,uma_klink)   uz_kegs;        /* List of kegs. */
        struct uma_klink        uz_klink;       /* klink for first keg. */

        uma_slaballoc   uz_slab;        /* Allocate a slab from the backend. */
        uma_ctor        uz_ctor;        /* Constructor for each allocation */
        uma_dtor        uz_dtor;        /* Destructor */
        uma_init        uz_init;        /* Initializer for each item */
        uma_fini        uz_fini;        /* Discards memory */

        u_int32_t       uz_flags;       /* Flags inherited from kegs */
        u_int32_t       uz_size;        /* Size inherited from kegs */

        u_int64_t       uz_allocs UMA_ALIGN; /* Total number of allocations */
        u_int64_t       uz_frees;       /* Total number of frees */
        u_int64_t       uz_fails;       /* Total number of alloc failures */
        u_int64_t       uz_sleeps;      /* Total number of alloc sleeps */
        uint16_t        uz_fills;       /* Outstanding bucket fills */
        uint16_t        uz_count;       /* Highest value ub_ptr can have */

        /*
         * This HAS to be the last item because we adjust the zone size
         * based on NCPU and then allocate the space for the zones.
         */
        struct uma_cache        uz_cpu[1]; /* Per cpu caches */
};

/*
 * These flags must not overlap with the UMA_ZONE flags specified in uma.h.
 */
#define UMA_ZFLAG_BUCKET        0x02000000      /* Bucket zone. */
#define UMA_ZFLAG_MULTI         0x04000000      /* Multiple kegs in the zone. */
#define UMA_ZFLAG_DRAINING      0x08000000      /* Running zone_drain. */
#define UMA_ZFLAG_PRIVALLOC     0x10000000      /* Use uz_allocf. */
#define UMA_ZFLAG_INTERNAL      0x20000000      /* No offpage no PCPU. */
#define UMA_ZFLAG_FULL          0x40000000      /* Reached uz_maxpages */
#define UMA_ZFLAG_CACHEONLY     0x80000000      /* Don't ask VM for buckets. */

#define UMA_ZFLAG_INHERIT       (UMA_ZFLAG_INTERNAL | UMA_ZFLAG_CACHEONLY | \
                                    UMA_ZFLAG_BUCKET)

#undef UMA_ALIGN

#ifdef _KERNEL
/* Internal prototypes */
static __inline uma_slab_t hash_sfind(struct uma_hash *hash, u_int8_t *data);
void *uma_large_malloc(int size, int wait);
void uma_large_free(uma_slab_t slab);

/* Lock Macros */

#define KEG_LOCK_INIT(k, lc)                                    \
        do {                                                    \
                if ((lc))                                       \
                        mtx_init(&(k)->uk_lock, (k)->uk_name,   \
                            (k)->uk_name, MTX_DEF | MTX_DUPOK); \
                else                                            \
                        mtx_init(&(k)->uk_lock, (k)->uk_name,   \
                            "UMA zone", MTX_DEF | MTX_DUPOK);   \
        } while (0)
            
#define KEG_LOCK_FINI(k)        mtx_destroy(&(k)->uk_lock)
#define KEG_LOCK(k)     mtx_lock(&(k)->uk_lock)
#define KEG_UNLOCK(k)   mtx_unlock(&(k)->uk_lock)
#define ZONE_LOCK(z)    mtx_lock((z)->uz_lock)
#define ZONE_UNLOCK(z)  mtx_unlock((z)->uz_lock)

/*
 * Find a slab within a hash table.  This is used for OFFPAGE zones to lookup
 * the slab structure.
 *
 * Arguments:
 *      hash  The hash table to search.
 *      data  The base page of the item.
 *
 * Returns:
 *      A pointer to a slab if successful, else NULL.
 */
static __inline uma_slab_t
hash_sfind(struct uma_hash *hash, u_int8_t *data)
{
        uma_slab_t slab;
        int hval;

        hval = UMA_HASH(hash, data);

        SLIST_FOREACH(slab, &hash->uh_slab_hash[hval], us_hlink) {
                if ((u_int8_t *)slab->us_data == data)
                        return (slab);
        }
        return (NULL);
}

#ifdef __rtems__
#include <machine/rtems-bsd-page.h>
#endif /* __rtems__ */
static __inline uma_slab_t
vtoslab(vm_offset_t va)
{
#ifndef __rtems__
        vm_page_t p;
        uma_slab_t slab;

        p = PHYS_TO_VM_PAGE(pmap_kextract(va));
        slab = (uma_slab_t )p->object;

        if (p->flags & PG_SLAB)
                return (slab);
        else
                return (NULL);
#else /* __rtems__ */
        return (rtems_bsd_page_get_object((void *)va));
#endif /* __rtems__ */
}

static __inline void
vsetslab(vm_offset_t va, uma_slab_t slab)
{
#ifndef __rtems__
        vm_page_t p;

        p = PHYS_TO_VM_PAGE(pmap_kextract(va));
        p->object = (vm_object_t)slab;
        p->flags |= PG_SLAB;
#else /* __rtems__ */
        rtems_bsd_page_set_object((void *)va, slab);
#endif /* __rtems__ */
}

#ifndef __rtems__
static __inline void
vsetobj(vm_offset_t va, vm_object_t obj)
{
        vm_page_t p;

        p = PHYS_TO_VM_PAGE(pmap_kextract(va));
        p->object = obj;
        p->flags &= ~PG_SLAB;
}
#endif /* __rtems__ */

/*
 * The following two functions may be defined by architecture specific code
 * if they can provide more effecient allocation functions.  This is useful
 * for using direct mapped addresses.
 */
void *uma_small_alloc(uma_zone_t zone, int bytes, u_int8_t *pflag, int wait);
void uma_small_free(void *mem, int size, u_int8_t flags);
#endif /* _KERNEL */

#endif /* VM_UMA_INT_H */