FreeBSD/Linux Kernel Cross Reference
sys/vm/uma_int.h

     /*
      * Copyright (c) 2002, Jeffrey Roberson <jeff@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: releng/5.3/sys/vm/uma_int.h 132842 2004-07-29 15:25:40Z bmilekic $
     *
     */
    
    /* 
     * 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 indexes, 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 indexes and only use
     * large slab sizes for zones with a lot of waste per slab.  This may create
     * ineffeciencies 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 their own locks, 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          40      /* 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 */
   };
   
   /*
    * 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 */
   };
   
   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;
   
           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_int16_t       uk_flags;       /* Internal flags */
   };
   
   /* Simpler reference to uma_keg for internal use. */
   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;
   
   /*
    * 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))
   
   /*
    * Zone management structure 
    *
    * TODO: Optimize for cache line size
    *
    */
   struct uma_zone {
           char            *uz_name;       /* Text name of the zone */
           struct mtx      *uz_lock;       /* Lock for the zone (keg's lock) */
           uma_keg_t       uz_keg;         /* Our underlying Keg */
   
           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 */
   
           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_int64_t       uz_allocs;      /* Total number of allocations */
           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_PRIVALLOC     0x1000          /* Use uz_allocf. */
   #define UMA_ZFLAG_INTERNAL      0x2000          /* No offpage no PCPU. */
   #define UMA_ZFLAG_FULL          0x4000          /* Reached uz_maxpages */
   #define UMA_ZFLAG_CACHEONLY     0x8000          /* Don't ask VM for buckets. */
   
   /* 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 ZONE_LOCK_INIT(z, lc)                                   \
           do {                                                    \
                   if ((lc))                                       \
                           mtx_init((z)->uz_lock, (z)->uz_name,    \
                               (z)->uz_name, MTX_DEF | MTX_DUPOK); \
                   else                                            \
                           mtx_init((z)->uz_lock, (z)->uz_name,    \
                               "UMA zone", MTX_DEF | MTX_DUPOK);   \
           } while (0)
               
   #define ZONE_LOCK_FINI(z)       mtx_destroy((z)->uz_lock)
   #define ZONE_LOCK(z)    mtx_lock((z)->uz_lock)
   #define ZONE_UNLOCK(z)  mtx_unlock((z)->uz_lock)
   
   #define CPU_LOCK_INIT(cpu)                                      \
           mtx_init(&uma_pcpu_mtx[(cpu)], "UMA pcpu", "UMA pcpu",  \
               MTX_DEF | MTX_DUPOK)
   
   #define CPU_LOCK(cpu)                                           \
           mtx_lock(&uma_pcpu_mtx[(cpu)])
   
   #define CPU_UNLOCK(cpu)                                         \
           mtx_unlock(&uma_pcpu_mtx[(cpu)])
   
   /*
    * 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);
   }
   
   static __inline uma_slab_t
   vtoslab(vm_offset_t va)
   {
           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);
   }
   
   static __inline void
   vsetslab(vm_offset_t va, uma_slab_t slab)
   {
           vm_page_t p;
   
           p = PHYS_TO_VM_PAGE(pmap_kextract((vm_offset_t)va));
           p->object = (vm_object_t)slab;
           p->flags |= PG_SLAB;
   }
   
   static __inline void
   vsetobj(vm_offset_t va, vm_object_t obj)
   {
           vm_page_t p;
   
           p = PHYS_TO_VM_PAGE(pmap_kextract((vm_offset_t)va));
           p->object = obj;
           p->flags &= ~PG_SLAB;
   }
   
   /*
    * 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 /* VM_UMA_INT_H */

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