The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    1 /*
    2  * Copyright (c) 2002, Jeffrey Roberson <jeff@freebsd.org>
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice unmodified, this list of conditions, and the following
   10  *    disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  *
   15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   25  *
   26  * $FreeBSD: releng/5.2/sys/vm/uma_int.h 120262 2003-09-19 23:27:46Z jeff $
   27  *
   28  */
   29 
   30 /* 
   31  * This file includes definitions, structures, prototypes, and inlines that
   32  * should not be used outside of the actual implementation of UMA.
   33  */
   34 
   35 /* 
   36  * Here's a quick description of the relationship between the objects:
   37  *
   38  * Zones contain lists of slabs which are stored in either the full bin, empty
   39  * bin, or partially allocated bin, to reduce fragmentation.  They also contain
   40  * the user supplied value for size, which is adjusted for alignment purposes
   41  * and rsize is the result of that.  The zone also stores information for
   42  * managing a hash of page addresses that maps pages to uma_slab_t structures
   43  * for pages that don't have embedded uma_slab_t's.
   44  *  
   45  * The uma_slab_t may be embedded in a UMA_SLAB_SIZE chunk of memory or it may
   46  * be allocated off the page from a special slab zone.  The free list within a
   47  * slab is managed with a linked list of indexes, which are 8 bit values.  If
   48  * UMA_SLAB_SIZE is defined to be too large I will have to switch to 16bit
   49  * values.  Currently on alpha you can get 250 or so 32 byte items and on x86
   50  * you can get 250 or so 16byte items.  For item sizes that would yield more
   51  * than 10% memory waste we potentially allocate a separate uma_slab_t if this
   52  * will improve the number of items per slab that will fit.  
   53  *
   54  * Other potential space optimizations are storing the 8bit of linkage in space
   55  * wasted between items due to alignment problems.  This may yield a much better
   56  * memory footprint for certain sizes of objects.  Another alternative is to
   57  * increase the UMA_SLAB_SIZE, or allow for dynamic slab sizes.  I prefer
   58  * dynamic slab sizes because we could stick with 8 bit indexes and only use
   59  * large slab sizes for zones with a lot of waste per slab.  This may create
   60  * ineffeciencies in the vm subsystem due to fragmentation in the address space.
   61  *
   62  * The only really gross cases, with regards to memory waste, are for those
   63  * items that are just over half the page size.   You can get nearly 50% waste,
   64  * so you fall back to the memory footprint of the power of two allocator. I
   65  * have looked at memory allocation sizes on many of the machines available to
   66  * me, and there does not seem to be an abundance of allocations at this range
   67  * so at this time it may not make sense to optimize for it.  This can, of 
   68  * course, be solved with dynamic slab sizes.
   69  *
   70  */
   71 
   72 /*
   73  *      This is the representation for normal (Non OFFPAGE slab)
   74  *
   75  *      i == item
   76  *      s == slab pointer
   77  *
   78  *      <----------------  Page (UMA_SLAB_SIZE) ------------------>
   79  *      ___________________________________________________________
   80  *     | _  _  _  _  _  _  _  _  _  _  _  _  _  _  _   ___________ |
   81  *     ||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i| |slab header||
   82  *     ||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_| |___________|| 
   83  *     |___________________________________________________________|
   84  *
   85  *
   86  *      This is an OFFPAGE slab. These can be larger than UMA_SLAB_SIZE.
   87  *
   88  *      ___________________________________________________________
   89  *     | _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _   |
   90  *     ||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i|  |
   91  *     ||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_|  |
   92  *     |___________________________________________________________|
   93  *       ___________    ^
   94  *      |slab header|   |
   95  *      |___________|---*
   96  *
   97  */
   98 
   99 #ifndef VM_UMA_INT_H
  100 #define VM_UMA_INT_H
  101 
  102 #define UMA_SLAB_SIZE   PAGE_SIZE       /* How big are our slabs? */
  103 #define UMA_SLAB_MASK   (PAGE_SIZE - 1) /* Mask to get back to the page */
  104 #define UMA_SLAB_SHIFT  PAGE_SHIFT      /* Number of bits PAGE_MASK */
  105 
  106 #define UMA_BOOT_PAGES          30      /* Pages allocated for startup */
  107 
  108 /* Max waste before going to off page slab management */
  109 #define UMA_MAX_WASTE   (UMA_SLAB_SIZE / 10)
  110 
  111 /*
  112  * I doubt there will be many cases where this is exceeded. This is the initial
  113  * size of the hash table for uma_slabs that are managed off page. This hash
  114  * does expand by powers of two.  Currently it doesn't get smaller.
  115  */
  116 #define UMA_HASH_SIZE_INIT      32              
  117 
  118 /* 
  119  * I should investigate other hashing algorithms.  This should yield a low
  120  * number of collisions if the pages are relatively contiguous.
  121  *
  122  * This is the same algorithm that most processor caches use.
  123  *
  124  * I'm shifting and masking instead of % because it should be faster.
  125  */
  126 
  127 #define UMA_HASH(h, s) ((((unsigned long)s) >> UMA_SLAB_SHIFT) &        \
  128     (h)->uh_hashmask)
  129 
  130 #define UMA_HASH_INSERT(h, s, mem)                                      \
  131                 SLIST_INSERT_HEAD(&(h)->uh_slab_hash[UMA_HASH((h),      \
  132                     (mem))], (s), us_hlink);
  133 #define UMA_HASH_REMOVE(h, s, mem)                                      \
  134                 SLIST_REMOVE(&(h)->uh_slab_hash[UMA_HASH((h),           \
  135                     (mem))], (s), uma_slab, us_hlink);
  136 
  137 /* Page management structure */
  138 
  139 /* Sorry for the union, but space efficiency is important */
  140 struct uma_slab {
  141         uma_zone_t      us_zone;                /* Zone we live in */
  142         union {
  143                 LIST_ENTRY(uma_slab)    _us_link;       /* slabs in zone */
  144                 unsigned long   _us_size;       /* Size of allocation */
  145         } us_type;
  146         SLIST_ENTRY(uma_slab)   us_hlink;       /* Link for hash table */
  147         u_int8_t        *us_data;               /* First item */
  148         u_int8_t        us_flags;               /* Page flags see uma.h */
  149         u_int8_t        us_freecount;   /* How many are free? */
  150         u_int8_t        us_firstfree;   /* First free item index */
  151         u_int8_t        us_freelist[1]; /* Free List (actually larger) */
  152 };
  153 
  154 #define us_link us_type._us_link
  155 #define us_size us_type._us_size
  156 
  157 typedef struct uma_slab * uma_slab_t;
  158 
  159 /* Hash table for freed address -> slab translation */
  160 
  161 SLIST_HEAD(slabhead, uma_slab);
  162 
  163 struct uma_hash {
  164         struct slabhead *uh_slab_hash;  /* Hash table for slabs */
  165         int             uh_hashsize;    /* Current size of the hash table */
  166         int             uh_hashmask;    /* Mask used during hashing */
  167 };
  168 
  169 /*
  170  * Structures for per cpu queues.
  171  */
  172 
  173 struct uma_bucket {
  174         LIST_ENTRY(uma_bucket)  ub_link;        /* Link into the zone */
  175         int16_t ub_cnt;                         /* Count of free items. */
  176         int16_t ub_entries;                     /* Max items. */
  177         void    *ub_bucket[];                   /* actual allocation storage */
  178 };
  179 
  180 typedef struct uma_bucket * uma_bucket_t;
  181 
  182 struct uma_cache {
  183         uma_bucket_t    uc_freebucket;  /* Bucket we're freeing to */
  184         uma_bucket_t    uc_allocbucket; /* Bucket to allocate from */
  185         u_int64_t       uc_allocs;      /* Count of allocations */
  186 };
  187 
  188 typedef struct uma_cache * uma_cache_t;
  189 
  190 /*
  191  * Zone management structure 
  192  *
  193  * TODO: Optimize for cache line size
  194  *
  195  */
  196 struct uma_zone {
  197         char            *uz_name;       /* Text name of the zone */
  198         LIST_ENTRY(uma_zone)    uz_link;        /* List of all zones */
  199         u_int32_t       uz_align;       /* Alignment mask */
  200         u_int32_t       uz_pages;       /* Total page count */
  201 
  202 /* Used during alloc / free */
  203         struct mtx      uz_lock;        /* Lock for the zone */
  204         u_int32_t       uz_free;        /* Count of items free in slabs */
  205         u_int16_t       uz_ipers;       /* Items per slab */
  206         u_int16_t       uz_flags;       /* Internal flags */
  207 
  208         LIST_HEAD(,uma_slab)    uz_part_slab;   /* partially allocated slabs */
  209         LIST_HEAD(,uma_slab)    uz_free_slab;   /* empty slab list */
  210         LIST_HEAD(,uma_slab)    uz_full_slab;   /* full slabs */
  211         LIST_HEAD(,uma_bucket)  uz_full_bucket; /* full buckets */
  212         LIST_HEAD(,uma_bucket)  uz_free_bucket; /* Buckets for frees */
  213         u_int32_t       uz_size;        /* Requested size of each item */
  214         u_int32_t       uz_rsize;       /* Real size of each item */
  215 
  216         struct uma_hash uz_hash;
  217         u_int16_t       uz_pgoff;       /* Offset to uma_slab struct */
  218         u_int16_t       uz_ppera;       /* pages per allocation from backend */
  219 
  220         uma_ctor        uz_ctor;        /* Constructor for each allocation */
  221         uma_dtor        uz_dtor;        /* Destructor */
  222         u_int64_t       uz_allocs;      /* Total number of allocations */
  223 
  224         uma_init        uz_init;        /* Initializer for each item */
  225         uma_fini        uz_fini;        /* Discards memory */
  226         uma_alloc       uz_allocf;      /* Allocation function */
  227         uma_free        uz_freef;       /* Free routine */
  228         struct vm_object        *uz_obj;        /* Zone specific object */
  229         vm_offset_t     uz_kva;         /* Base kva for zones with objs */
  230         u_int32_t       uz_maxpages;    /* Maximum number of pages to alloc */
  231         int             uz_recurse;     /* Allocation recursion count */
  232         uint16_t        uz_fills;       /* Outstanding bucket fills */
  233         uint16_t        uz_count;       /* Highest value ub_ptr can have */
  234         /*
  235          * This HAS to be the last item because we adjust the zone size
  236          * based on NCPU and then allocate the space for the zones.
  237          */
  238         struct uma_cache        uz_cpu[1];      /* Per cpu caches */
  239 };
  240 
  241 /*
  242  * These flags must not overlap with the UMA_ZONE flags specified in uma.h.
  243  */
  244 #define UMA_ZFLAG_PRIVALLOC     0x1000          /* Use uz_allocf. */
  245 #define UMA_ZFLAG_INTERNAL      0x2000          /* No offpage no PCPU. */
  246 #define UMA_ZFLAG_FULL          0x4000          /* Reached uz_maxpages */
  247 #define UMA_ZFLAG_CACHEONLY     0x8000          /* Don't ask VM for buckets. */
  248 
  249 /* Internal prototypes */
  250 static __inline uma_slab_t hash_sfind(struct uma_hash *hash, u_int8_t *data);
  251 void *uma_large_malloc(int size, int wait);
  252 void uma_large_free(uma_slab_t slab);
  253 
  254 /* Lock Macros */
  255 
  256 #define ZONE_LOCK_INIT(z, lc)                                   \
  257         do {                                                    \
  258                 if ((lc))                                       \
  259                         mtx_init(&(z)->uz_lock, (z)->uz_name,   \
  260                             (z)->uz_name, MTX_DEF | MTX_DUPOK); \
  261                 else                                            \
  262                         mtx_init(&(z)->uz_lock, (z)->uz_name,   \
  263                             "UMA zone", MTX_DEF | MTX_DUPOK);   \
  264         } while (0)
  265             
  266 #define ZONE_LOCK_FINI(z)       mtx_destroy(&(z)->uz_lock)
  267 #define ZONE_LOCK(z)    mtx_lock(&(z)->uz_lock)
  268 #define ZONE_UNLOCK(z)  mtx_unlock(&(z)->uz_lock)
  269 
  270 #define CPU_LOCK_INIT(cpu)                                      \
  271         mtx_init(&uma_pcpu_mtx[(cpu)], "UMA pcpu", "UMA pcpu",  \
  272             MTX_DEF | MTX_DUPOK)
  273 
  274 #define CPU_LOCK(cpu)                                           \
  275         mtx_lock(&uma_pcpu_mtx[(cpu)])
  276 
  277 #define CPU_UNLOCK(cpu)                                         \
  278         mtx_unlock(&uma_pcpu_mtx[(cpu)])
  279 
  280 /*
  281  * Find a slab within a hash table.  This is used for OFFPAGE zones to lookup
  282  * the slab structure.
  283  *
  284  * Arguments:
  285  *      hash  The hash table to search.
  286  *      data  The base page of the item.
  287  *
  288  * Returns:
  289  *      A pointer to a slab if successful, else NULL.
  290  */
  291 static __inline uma_slab_t
  292 hash_sfind(struct uma_hash *hash, u_int8_t *data)
  293 {
  294         uma_slab_t slab;
  295         int hval;
  296 
  297         hval = UMA_HASH(hash, data);
  298 
  299         SLIST_FOREACH(slab, &hash->uh_slab_hash[hval], us_hlink) {
  300                 if ((u_int8_t *)slab->us_data == data)
  301                         return (slab);
  302         }
  303         return (NULL);
  304 }
  305 
  306 static __inline uma_slab_t
  307 vtoslab(vm_offset_t va)
  308 {
  309         vm_page_t p;
  310         uma_slab_t slab;
  311 
  312         p = PHYS_TO_VM_PAGE(pmap_kextract(va));
  313         slab = (uma_slab_t )p->object;
  314 
  315         if (p->flags & PG_SLAB)
  316                 return (slab);
  317         else
  318                 return (NULL);
  319 }
  320 
  321 static __inline void
  322 vsetslab(vm_offset_t va, uma_slab_t slab)
  323 {
  324         vm_page_t p;
  325 
  326         p = PHYS_TO_VM_PAGE(pmap_kextract((vm_offset_t)va));
  327         p->object = (vm_object_t)slab;
  328         p->flags |= PG_SLAB;
  329 }
  330 
  331 static __inline void
  332 vsetobj(vm_offset_t va, vm_object_t obj)
  333 {
  334         vm_page_t p;
  335 
  336         p = PHYS_TO_VM_PAGE(pmap_kextract((vm_offset_t)va));
  337         p->object = obj;
  338         p->flags &= ~PG_SLAB;
  339 }
  340 
  341 /*
  342  * The following two functions may be defined by architecture specific code
  343  * if they can provide more effecient allocation functions.  This is useful
  344  * for using direct mapped addresses.
  345  */
  346 void *uma_small_alloc(uma_zone_t zone, int bytes, u_int8_t *pflag, int wait);
  347 void uma_small_free(void *mem, int size, u_int8_t flags);
  348 
  349 #endif /* VM_UMA_INT_H */

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