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/5.0/sys/vm/uma_int.h 106277 2002-11-01 01:01:27Z 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      /* Number of pages allocated for startup */
  107 #define UMA_WORKING_TIME        20      /* Seconds worth of items to keep */
  108 
  109 
  110 /* Max waste before going to off page slab management */
  111 #define UMA_MAX_WASTE   (UMA_SLAB_SIZE / 10)
  112 
  113 /*
  114  * I doubt there will be many cases where this is exceeded. This is the initial
  115  * size of the hash table for uma_slabs that are managed off page. This hash
  116  * does expand by powers of two.  Currently it doesn't get smaller.
  117  */
  118 #define UMA_HASH_SIZE_INIT      32              
  119 
  120 
  121 /* 
  122  * I should investigate other hashing algorithms.  This should yield a low
  123  * number of collisions if the pages are relatively contiguous.
  124  *
  125  * This is the same algorithm that most processor caches use.
  126  *
  127  * I'm shifting and masking instead of % because it should be faster.
  128  */
  129 
  130 #define UMA_HASH(h, s) ((((unsigned long)s) >> UMA_SLAB_SHIFT) &        \
  131     (h)->uh_hashmask)
  132 
  133 #define UMA_HASH_INSERT(h, s, mem)                                      \
  134                 SLIST_INSERT_HEAD(&(h)->uh_slab_hash[UMA_HASH((h),      \
  135                     (mem))], (s), us_hlink);
  136 #define UMA_HASH_REMOVE(h, s, mem)                                      \
  137                 SLIST_REMOVE(&(h)->uh_slab_hash[UMA_HASH((h),           \
  138                     (mem))], (s), uma_slab, us_hlink);
  139 
  140 /* Page management structure */
  141 
  142 /* Sorry for the union, but space efficiency is important */
  143 struct uma_slab {
  144         uma_zone_t      us_zone;                /* Zone we live in */
  145         union {
  146                 LIST_ENTRY(uma_slab)    us_link;        /* slabs in zone */
  147                 unsigned long   us_size;        /* Size of allocation */
  148         } us_type;
  149         SLIST_ENTRY(uma_slab)   us_hlink;       /* Link for hash table */
  150         u_int8_t        *us_data;               /* First item */
  151         u_int8_t        us_flags;               /* Page flags see uma.h */
  152         u_int8_t        us_freecount;   /* How many are free? */
  153         u_int8_t        us_firstfree;   /* First free item index */
  154         u_int8_t        us_freelist[1]; /* Free List (actually larger) */
  155 };
  156 
  157 #define us_link us_type.us_link
  158 #define us_size us_type.us_size
  159 
  160 typedef struct uma_slab * uma_slab_t;
  161 
  162 /* Hash table for freed address -> slab translation */
  163 
  164 SLIST_HEAD(slabhead, uma_slab);
  165 
  166 struct uma_hash {
  167         struct slabhead *uh_slab_hash;  /* Hash table for slabs */
  168         int             uh_hashsize;    /* Current size of the hash table */
  169         int             uh_hashmask;    /* Mask used during hashing */
  170 };
  171 
  172 /*
  173  * Structures for per cpu queues.
  174  */
  175 
  176 /*
  177  * This size was chosen so that the struct bucket size is roughly
  178  * 128 * sizeof(void *).  This is exactly true for x86, and for alpha
  179  * it will would be 32bits smaller if it didn't have alignment adjustments.
  180  */
  181 
  182 #define UMA_BUCKET_SIZE 125
  183 
  184 struct uma_bucket {
  185         LIST_ENTRY(uma_bucket)  ub_link;        /* Link into the zone */
  186         int16_t ub_ptr;                         /* Pointer to current item */
  187         void    *ub_bucket[UMA_BUCKET_SIZE];    /* actual allocation storage */
  188 };
  189 
  190 typedef struct uma_bucket * uma_bucket_t;
  191 
  192 struct uma_cache {
  193         struct mtx      uc_lock;        /* Spin lock on this cpu's bucket */
  194         uma_bucket_t    uc_freebucket;  /* Bucket we're freeing to */
  195         uma_bucket_t    uc_allocbucket; /* Bucket to allocate from */
  196         u_int64_t       uc_allocs;      /* Count of allocations */
  197 };
  198 
  199 typedef struct uma_cache * uma_cache_t;
  200 
  201 #define LOCKNAME_LEN    16              /* Length of the name for cpu locks */
  202 
  203 /*
  204  * Zone management structure 
  205  *
  206  * TODO: Optimize for cache line size
  207  *
  208  */
  209 struct uma_zone {
  210         char            uz_lname[LOCKNAME_LEN]; /* Text name for the cpu lock */
  211         char            *uz_name;       /* Text name of the zone */
  212         LIST_ENTRY(uma_zone)    uz_link;        /* List of all zones */
  213         u_int32_t       uz_align;       /* Alignment mask */
  214         u_int32_t       uz_pages;       /* Total page count */
  215 
  216 /* Used during alloc / free */
  217         struct mtx      uz_lock;        /* Lock for the zone */
  218         u_int32_t       uz_free;        /* Count of items free in slabs */
  219         u_int16_t       uz_ipers;       /* Items per slab */
  220         u_int16_t       uz_flags;       /* Internal flags */
  221 
  222         LIST_HEAD(,uma_slab)    uz_part_slab;   /* partially allocated slabs */
  223         LIST_HEAD(,uma_slab)    uz_free_slab;   /* empty slab list */
  224         LIST_HEAD(,uma_slab)    uz_full_slab;   /* full slabs */
  225         LIST_HEAD(,uma_bucket)  uz_full_bucket; /* full buckets */
  226         LIST_HEAD(,uma_bucket)  uz_free_bucket; /* Buckets for frees */
  227         u_int32_t       uz_size;        /* Requested size of each item */
  228         u_int32_t       uz_rsize;       /* Real size of each item */
  229 
  230         struct uma_hash uz_hash;
  231         u_int16_t       uz_pgoff;       /* Offset to uma_slab struct */
  232         u_int16_t       uz_ppera;       /* pages per allocation from backend */
  233         u_int16_t       uz_cacheoff;    /* Next cache offset */
  234         u_int16_t       uz_cachemax;    /* Max cache offset */
  235 
  236         uma_ctor        uz_ctor;        /* Constructor for each allocation */
  237         uma_dtor        uz_dtor;        /* Destructor */
  238         u_int64_t       uz_allocs;      /* Total number of allocations */
  239 
  240         uma_init        uz_init;        /* Initializer for each item */
  241         uma_fini        uz_fini;        /* Discards memory */
  242         uma_alloc       uz_allocf;      /* Allocation function */
  243         uma_free        uz_freef;       /* Free routine */
  244         struct vm_object        *uz_obj;        /* Zone specific object */
  245         vm_offset_t     uz_kva;         /* Base kva for zones with objs */
  246         u_int32_t       uz_maxpages;    /* Maximum number of pages to alloc */
  247         u_int32_t       uz_cachefree;   /* Last count of items free in caches */
  248         u_int64_t       uz_oallocs;     /* old allocs count */
  249         u_int64_t       uz_wssize;      /* Working set size */
  250         int             uz_recurse;     /* Allocation recursion count */
  251         uint16_t        uz_fills;       /* Outstanding bucket fills */
  252         uint16_t        uz_count;       /* Highest value ub_ptr can have */
  253         /*
  254          * This HAS to be the last item because we adjust the zone size
  255          * based on NCPU and then allocate the space for the zones.
  256          */
  257         struct uma_cache        uz_cpu[1];      /* Per cpu caches */
  258 };
  259 
  260 #define UMA_CACHE_INC   16      /* How much will we move data */
  261 
  262 #define UMA_ZFLAG_OFFPAGE       0x0001  /* Struct slab/freelist off page */
  263 #define UMA_ZFLAG_PRIVALLOC     0x0002  /* Zone has supplied it's own alloc */
  264 #define UMA_ZFLAG_INTERNAL      0x0004  /* Internal zone, no offpage no PCPU */
  265 #define UMA_ZFLAG_MALLOC        0x0008  /* Zone created by malloc */
  266 #define UMA_ZFLAG_NOFREE        0x0010  /* Don't free data from this zone */
  267 #define UMA_ZFLAG_FULL          0x0020  /* This zone reached uz_maxpages */
  268 #define UMA_ZFLAG_BUCKETCACHE   0x0040  /* Only allocate buckets from cache */
  269 #define UMA_ZFLAG_HASH          0x0080  /* Look up slab via hash */
  270 
  271 /* This lives in uflags */
  272 #define UMA_ZONE_INTERNAL       0x1000  /* Internal zone for uflags */
  273 
  274 /* Internal prototypes */
  275 static __inline uma_slab_t hash_sfind(struct uma_hash *hash, u_int8_t *data);
  276 void *uma_large_malloc(int size, int wait);
  277 void uma_large_free(uma_slab_t slab);
  278 
  279 /* Lock Macros */
  280 
  281 #define ZONE_LOCK_INIT(z, lc)                                   \
  282         do {                                                    \
  283                 if ((lc))                                       \
  284                         mtx_init(&(z)->uz_lock, (z)->uz_name,   \
  285                             (z)->uz_name, MTX_DEF | MTX_DUPOK); \
  286                 else                                            \
  287                         mtx_init(&(z)->uz_lock, (z)->uz_name,   \
  288                             "UMA zone", MTX_DEF | MTX_DUPOK);   \
  289         } while (0)
  290             
  291 #define ZONE_LOCK_FINI(z)       mtx_destroy(&(z)->uz_lock)
  292 #define ZONE_LOCK(z)    mtx_lock(&(z)->uz_lock)
  293 #define ZONE_UNLOCK(z)  mtx_unlock(&(z)->uz_lock)
  294 
  295 #define CPU_LOCK_INIT(z, cpu, lc)                               \
  296         do {                                                    \
  297                 if ((lc))                                       \
  298                         mtx_init(&(z)->uz_cpu[(cpu)].uc_lock,   \
  299                             (z)->uz_lname, (z)->uz_lname,       \
  300                             MTX_DEF | MTX_DUPOK);               \
  301                 else                                            \
  302                         mtx_init(&(z)->uz_cpu[(cpu)].uc_lock,   \
  303                             (z)->uz_lname, "UMA cpu",           \
  304                             MTX_DEF | MTX_DUPOK);               \
  305         } while (0)
  306 
  307 #define CPU_LOCK_FINI(z, cpu)   \
  308         mtx_destroy(&(z)->uz_cpu[(cpu)].uc_lock)
  309 
  310 #define CPU_LOCK(z, cpu)        \
  311         mtx_lock(&(z)->uz_cpu[(cpu)].uc_lock)
  312 
  313 #define CPU_UNLOCK(z, cpu)      \
  314         mtx_unlock(&(z)->uz_cpu[(cpu)].uc_lock)
  315 
  316 /*
  317  * Find a slab within a hash table.  This is used for OFFPAGE zones to lookup
  318  * the slab structure.
  319  *
  320  * Arguments:
  321  *      hash  The hash table to search.
  322  *      data  The base page of the item.
  323  *
  324  * Returns:
  325  *      A pointer to a slab if successful, else NULL.
  326  */
  327 static __inline uma_slab_t
  328 hash_sfind(struct uma_hash *hash, u_int8_t *data)
  329 {
  330         uma_slab_t slab;
  331         int hval;
  332 
  333         hval = UMA_HASH(hash, data);
  334 
  335         SLIST_FOREACH(slab, &hash->uh_slab_hash[hval], us_hlink) {
  336                 if ((u_int8_t *)slab->us_data == data)
  337                         return (slab);
  338         }
  339         return (NULL);
  340 }
  341 
  342 static __inline uma_slab_t
  343 vtoslab(vm_offset_t va)
  344 {
  345         vm_page_t p;
  346         uma_slab_t slab;
  347 
  348         p = PHYS_TO_VM_PAGE(pmap_kextract(va));
  349         slab = (uma_slab_t )p->object;
  350 
  351         if (p->flags & PG_SLAB)
  352                 return (slab);
  353         else
  354                 return (NULL);
  355 }
  356 
  357 static __inline void
  358 vsetslab(vm_offset_t va, uma_slab_t slab)
  359 {
  360         vm_page_t p;
  361 
  362         p = PHYS_TO_VM_PAGE(pmap_kextract((vm_offset_t)va));
  363         p->object = (vm_object_t)slab;
  364         p->flags |= PG_SLAB;
  365 }
  366 
  367 static __inline void
  368 vsetobj(vm_offset_t va, vm_object_t obj)
  369 {
  370         vm_page_t p;
  371 
  372         p = PHYS_TO_VM_PAGE(pmap_kextract((vm_offset_t)va));
  373         p->object = obj;
  374         p->flags &= ~PG_SLAB;
  375 }
  376 
  377 /*
  378  * The following two functions may be defined by architecture specific code
  379  * if they can provide more effecient allocation functions.  This is useful
  380  * for using direct mapped addresses.
  381  */
  382 void *uma_small_alloc(uma_zone_t zone, int bytes, u_int8_t *pflag, int wait);
  383 void uma_small_free(void *mem, int size, u_int8_t flags);
  384 
  385 #endif /* VM_UMA_INT_H */

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