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) 2002-2005, 2009, 2013 Jeffrey Roberson <jeff@FreeBSD.org>
    3  * Copyright (c) 2004, 2005 Bosko Milekic <bmilekic@FreeBSD.org>
    4  * All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice unmodified, this list of conditions, and the following
   11  *    disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   26  *
   27  * $FreeBSD: releng/10.2/sys/vm/uma_int.h 281943 2015-04-24 17:05:18Z scottl $
   28  *
   29  */
   30 
   31 /* 
   32  * This file includes definitions, structures, prototypes, and inlines that
   33  * should not be used outside of the actual implementation of UMA.
   34  */
   35 
   36 /* 
   37  * Here's a quick description of the relationship between the objects:
   38  *
   39  * Kegs contain lists of slabs which are stored in either the full bin, empty
   40  * bin, or partially allocated bin, to reduce fragmentation.  They also contain
   41  * the user supplied value for size, which is adjusted for alignment purposes
   42  * and rsize is the result of that.  The Keg also stores information for
   43  * managing a hash of page addresses that maps pages to uma_slab_t structures
   44  * for pages that don't have embedded uma_slab_t's.
   45  *  
   46  * The uma_slab_t may be embedded in a UMA_SLAB_SIZE chunk of memory or it may
   47  * be allocated off the page from a special slab zone.  The free list within a
   48  * slab is managed with a bitmask.  For item sizes that would yield more than
   49  * 10% memory waste we potentially allocate a separate uma_slab_t if this will
   50  * improve the number of items per slab that will fit.  
   51  *
   52  * The only really gross cases, with regards to memory waste, are for those
   53  * items that are just over half the page size.   You can get nearly 50% waste,
   54  * so you fall back to the memory footprint of the power of two allocator. I
   55  * have looked at memory allocation sizes on many of the machines available to
   56  * me, and there does not seem to be an abundance of allocations at this range
   57  * so at this time it may not make sense to optimize for it.  This can, of 
   58  * course, be solved with dynamic slab sizes.
   59  *
   60  * Kegs may serve multiple Zones but by far most of the time they only serve
   61  * one.  When a Zone is created, a Keg is allocated and setup for it.  While
   62  * the backing Keg stores slabs, the Zone caches Buckets of items allocated
   63  * from the slabs.  Each Zone is equipped with an init/fini and ctor/dtor
   64  * pair, as well as with its own set of small per-CPU caches, layered above
   65  * the Zone's general Bucket cache.
   66  *
   67  * The PCPU caches are protected by critical sections, and may be accessed
   68  * safely only from their associated CPU, while the Zones backed by the same
   69  * Keg all share a common Keg lock (to coalesce contention on the backing
   70  * slabs).  The backing Keg typically only serves one Zone but in the case of
   71  * multiple Zones, one of the Zones is considered the Master Zone and all
   72  * Zone-related stats from the Keg are done in the Master Zone.  For an
   73  * example of a Multi-Zone setup, refer to the Mbuf allocation code.
   74  */
   75 
   76 /*
   77  *      This is the representation for normal (Non OFFPAGE slab)
   78  *
   79  *      i == item
   80  *      s == slab pointer
   81  *
   82  *      <----------------  Page (UMA_SLAB_SIZE) ------------------>
   83  *      ___________________________________________________________
   84  *     | _  _  _  _  _  _  _  _  _  _  _  _  _  _  _   ___________ |
   85  *     ||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i| |slab header||
   86  *     ||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_| |___________|| 
   87  *     |___________________________________________________________|
   88  *
   89  *
   90  *      This is an OFFPAGE slab. These can be larger than UMA_SLAB_SIZE.
   91  *
   92  *      ___________________________________________________________
   93  *     | _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _  _   |
   94  *     ||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i|  |
   95  *     ||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_|  |
   96  *     |___________________________________________________________|
   97  *       ___________    ^
   98  *      |slab header|   |
   99  *      |___________|---*
  100  *
  101  */
  102 
  103 #ifndef VM_UMA_INT_H
  104 #define VM_UMA_INT_H
  105 
  106 #define UMA_SLAB_SIZE   PAGE_SIZE       /* How big are our slabs? */
  107 #define UMA_SLAB_MASK   (PAGE_SIZE - 1) /* Mask to get back to the page */
  108 #define UMA_SLAB_SHIFT  PAGE_SHIFT      /* Number of bits PAGE_MASK */
  109 
  110 #define UMA_BOOT_PAGES          64      /* Pages allocated for startup */
  111 
  112 /* Max waste percentage before going to off page slab management */
  113 #define UMA_MAX_WASTE   10
  114 
  115 /*
  116  * I doubt there will be many cases where this is exceeded. This is the initial
  117  * size of the hash table for uma_slabs that are managed off page. This hash
  118  * does expand by powers of two.  Currently it doesn't get smaller.
  119  */
  120 #define UMA_HASH_SIZE_INIT      32              
  121 
  122 /* 
  123  * I should investigate other hashing algorithms.  This should yield a low
  124  * number of collisions if the pages are relatively contiguous.
  125  */
  126 
  127 #define UMA_HASH(h, s) ((((uintptr_t)s) >> UMA_SLAB_SHIFT) & (h)->uh_hashmask)
  128 
  129 #define UMA_HASH_INSERT(h, s, mem)                                      \
  130                 SLIST_INSERT_HEAD(&(h)->uh_slab_hash[UMA_HASH((h),      \
  131                     (mem))], (s), us_hlink)
  132 #define UMA_HASH_REMOVE(h, s, mem)                                      \
  133                 SLIST_REMOVE(&(h)->uh_slab_hash[UMA_HASH((h),           \
  134                     (mem))], (s), uma_slab, us_hlink)
  135 
  136 /* Hash table for freed address -> slab translation */
  137 
  138 SLIST_HEAD(slabhead, uma_slab);
  139 
  140 struct uma_hash {
  141         struct slabhead *uh_slab_hash;  /* Hash table for slabs */
  142         int             uh_hashsize;    /* Current size of the hash table */
  143         int             uh_hashmask;    /* Mask used during hashing */
  144 };
  145 
  146 /*
  147  * align field or structure to cache line
  148  */
  149 #if defined(__amd64__)
  150 #define UMA_ALIGN       __aligned(CACHE_LINE_SIZE)
  151 #else
  152 #define UMA_ALIGN
  153 #endif
  154 
  155 /*
  156  * Structures for per cpu queues.
  157  */
  158 
  159 struct uma_bucket {
  160         LIST_ENTRY(uma_bucket)  ub_link;        /* Link into the zone */
  161         int16_t ub_cnt;                         /* Count of free items. */
  162         int16_t ub_entries;                     /* Max items. */
  163         void    *ub_bucket[];                   /* actual allocation storage */
  164 };
  165 
  166 typedef struct uma_bucket * uma_bucket_t;
  167 
  168 struct uma_cache {
  169         uma_bucket_t    uc_freebucket;  /* Bucket we're freeing to */
  170         uma_bucket_t    uc_allocbucket; /* Bucket to allocate from */
  171         uint64_t        uc_allocs;      /* Count of allocations */
  172         uint64_t        uc_frees;       /* Count of frees */
  173 } UMA_ALIGN;
  174 
  175 typedef struct uma_cache * uma_cache_t;
  176 
  177 /*
  178  * Keg management structure
  179  *
  180  * TODO: Optimize for cache line size
  181  *
  182  */
  183 struct uma_keg {
  184         struct mtx_padalign     uk_lock;        /* Lock for the keg */
  185         struct uma_hash uk_hash;
  186 
  187         LIST_HEAD(,uma_zone)    uk_zones;       /* Keg's zones */
  188         LIST_HEAD(,uma_slab)    uk_part_slab;   /* partially allocated slabs */
  189         LIST_HEAD(,uma_slab)    uk_free_slab;   /* empty slab list */
  190         LIST_HEAD(,uma_slab)    uk_full_slab;   /* full slabs */
  191 
  192         uint32_t        uk_align;       /* Alignment mask */
  193         uint32_t        uk_pages;       /* Total page count */
  194         uint32_t        uk_free;        /* Count of items free in slabs */
  195         uint32_t        uk_reserve;     /* Number of reserved items. */
  196         uint32_t        uk_size;        /* Requested size of each item */
  197         uint32_t        uk_rsize;       /* Real size of each item */
  198         uint32_t        uk_maxpages;    /* Maximum number of pages to alloc */
  199 
  200         uma_init        uk_init;        /* Keg's init routine */
  201         uma_fini        uk_fini;        /* Keg's fini routine */
  202         uma_alloc       uk_allocf;      /* Allocation function */
  203         uma_free        uk_freef;       /* Free routine */
  204 
  205         u_long          uk_offset;      /* Next free offset from base KVA */
  206         vm_offset_t     uk_kva;         /* Zone base KVA */
  207         uma_zone_t      uk_slabzone;    /* Slab zone backing us, if OFFPAGE */
  208 
  209         uint16_t        uk_slabsize;    /* Slab size for this keg */
  210         uint16_t        uk_pgoff;       /* Offset to uma_slab struct */
  211         uint16_t        uk_ppera;       /* pages per allocation from backend */
  212         uint16_t        uk_ipers;       /* Items per slab */
  213         uint32_t        uk_flags;       /* Internal flags */
  214 
  215         /* Least used fields go to the last cache line. */
  216         const char      *uk_name;               /* Name of creating zone. */
  217         LIST_ENTRY(uma_keg)     uk_link;        /* List of all kegs */
  218 };
  219 typedef struct uma_keg  * uma_keg_t;
  220 
  221 /*
  222  * Free bits per-slab.
  223  */
  224 #define SLAB_SETSIZE    (PAGE_SIZE / UMA_SMALLEST_UNIT)
  225 BITSET_DEFINE(slabbits, SLAB_SETSIZE);
  226 
  227 /*
  228  * The slab structure manages a single contiguous allocation from backing
  229  * store and subdivides it into individually allocatable items.
  230  */
  231 struct uma_slab {
  232         uma_keg_t       us_keg;                 /* Keg we live in */
  233         union {
  234                 LIST_ENTRY(uma_slab)    _us_link;       /* slabs in zone */
  235                 unsigned long   _us_size;       /* Size of allocation */
  236         } us_type;
  237         SLIST_ENTRY(uma_slab)   us_hlink;       /* Link for hash table */
  238         uint8_t         *us_data;               /* First item */
  239         struct slabbits us_free;                /* Free bitmask. */
  240 #ifdef INVARIANTS
  241         struct slabbits us_debugfree;           /* Debug bitmask. */
  242 #endif
  243         uint16_t        us_freecount;           /* How many are free? */
  244         uint8_t         us_flags;               /* Page flags see uma.h */
  245         uint8_t         us_pad;                 /* Pad to 32bits, unused. */
  246 };
  247 
  248 #define us_link us_type._us_link
  249 #define us_size us_type._us_size
  250 
  251 /*
  252  * The slab structure for UMA_ZONE_REFCNT zones for whose items we
  253  * maintain reference counters in the slab for.
  254  */
  255 struct uma_slab_refcnt {
  256         struct uma_slab         us_head;        /* slab header data */
  257         uint32_t                us_refcnt[0];   /* Actually larger. */
  258 };
  259 
  260 typedef struct uma_slab * uma_slab_t;
  261 typedef struct uma_slab_refcnt * uma_slabrefcnt_t;
  262 typedef uma_slab_t (*uma_slaballoc)(uma_zone_t, uma_keg_t, int);
  263 
  264 struct uma_klink {
  265         LIST_ENTRY(uma_klink)   kl_link;
  266         uma_keg_t               kl_keg;
  267 };
  268 typedef struct uma_klink *uma_klink_t;
  269 
  270 /*
  271  * Zone management structure 
  272  *
  273  * TODO: Optimize for cache line size
  274  *
  275  */
  276 struct uma_zone {
  277         struct mtx_padalign     uz_lock;        /* Lock for the zone */
  278         struct mtx_padalign     *uz_lockptr;
  279         const char              *uz_name;       /* Text name of the zone */
  280 
  281         LIST_ENTRY(uma_zone)    uz_link;        /* List of all zones in keg */
  282         LIST_HEAD(,uma_bucket)  uz_buckets;     /* full buckets */
  283 
  284         LIST_HEAD(,uma_klink)   uz_kegs;        /* List of kegs. */
  285         struct uma_klink        uz_klink;       /* klink for first keg. */
  286 
  287         uma_slaballoc   uz_slab;        /* Allocate a slab from the backend. */
  288         uma_ctor        uz_ctor;        /* Constructor for each allocation */
  289         uma_dtor        uz_dtor;        /* Destructor */
  290         uma_init        uz_init;        /* Initializer for each item */
  291         uma_fini        uz_fini;        /* Finalizer for each item. */
  292         uma_import      uz_import;      /* Import new memory to cache. */
  293         uma_release     uz_release;     /* Release memory from cache. */
  294         void            *uz_arg;        /* Import/release argument. */
  295 
  296         uint32_t        uz_flags;       /* Flags inherited from kegs */
  297         uint32_t        uz_size;        /* Size inherited from kegs */
  298 
  299         volatile u_long uz_allocs UMA_ALIGN; /* Total number of allocations */
  300         volatile u_long uz_fails;       /* Total number of alloc failures */
  301         volatile u_long uz_frees;       /* Total number of frees */
  302         uint64_t        uz_sleeps;      /* Total number of alloc sleeps */
  303         uint16_t        uz_count;       /* Amount of items in full bucket */
  304         uint16_t        uz_count_min;   /* Minimal amount of items there */
  305 
  306         /* The next three fields are used to print a rate-limited warnings. */
  307         const char      *uz_warning;    /* Warning to print on failure */
  308         struct timeval  uz_ratecheck;   /* Warnings rate-limiting */
  309 
  310         /*
  311          * This HAS to be the last item because we adjust the zone size
  312          * based on NCPU and then allocate the space for the zones.
  313          */
  314         struct uma_cache        uz_cpu[1]; /* Per cpu caches */
  315 };
  316 
  317 /*
  318  * These flags must not overlap with the UMA_ZONE flags specified in uma.h.
  319  */
  320 #define UMA_ZFLAG_MULTI         0x04000000      /* Multiple kegs in the zone. */
  321 #define UMA_ZFLAG_DRAINING      0x08000000      /* Running zone_drain. */
  322 #define UMA_ZFLAG_BUCKET        0x10000000      /* Bucket zone. */
  323 #define UMA_ZFLAG_INTERNAL      0x20000000      /* No offpage no PCPU. */
  324 #define UMA_ZFLAG_FULL          0x40000000      /* Reached uz_maxpages */
  325 #define UMA_ZFLAG_CACHEONLY     0x80000000      /* Don't ask VM for buckets. */
  326 
  327 #define UMA_ZFLAG_INHERIT                                               \
  328     (UMA_ZFLAG_INTERNAL | UMA_ZFLAG_CACHEONLY | UMA_ZFLAG_BUCKET)
  329 
  330 static inline uma_keg_t
  331 zone_first_keg(uma_zone_t zone)
  332 {
  333         uma_klink_t klink;
  334 
  335         klink = LIST_FIRST(&zone->uz_kegs);
  336         return (klink != NULL) ? klink->kl_keg : NULL;
  337 }
  338 
  339 #undef UMA_ALIGN
  340 
  341 #ifdef _KERNEL
  342 /* Internal prototypes */
  343 static __inline uma_slab_t hash_sfind(struct uma_hash *hash, uint8_t *data);
  344 void *uma_large_malloc(int size, int wait);
  345 void uma_large_free(uma_slab_t slab);
  346 
  347 /* Lock Macros */
  348 
  349 #define KEG_LOCK_INIT(k, lc)                                    \
  350         do {                                                    \
  351                 if ((lc))                                       \
  352                         mtx_init(&(k)->uk_lock, (k)->uk_name,   \
  353                             (k)->uk_name, MTX_DEF | MTX_DUPOK); \
  354                 else                                            \
  355                         mtx_init(&(k)->uk_lock, (k)->uk_name,   \
  356                             "UMA zone", MTX_DEF | MTX_DUPOK);   \
  357         } while (0)
  358 
  359 #define KEG_LOCK_FINI(k)        mtx_destroy(&(k)->uk_lock)
  360 #define KEG_LOCK(k)     mtx_lock(&(k)->uk_lock)
  361 #define KEG_UNLOCK(k)   mtx_unlock(&(k)->uk_lock)
  362 
  363 #define ZONE_LOCK_INIT(z, lc)                                   \
  364         do {                                                    \
  365                 if ((lc))                                       \
  366                         mtx_init(&(z)->uz_lock, (z)->uz_name,   \
  367                             (z)->uz_name, MTX_DEF | MTX_DUPOK); \
  368                 else                                            \
  369                         mtx_init(&(z)->uz_lock, (z)->uz_name,   \
  370                             "UMA zone", MTX_DEF | MTX_DUPOK);   \
  371         } while (0)
  372             
  373 #define ZONE_LOCK(z)    mtx_lock((z)->uz_lockptr)
  374 #define ZONE_TRYLOCK(z) mtx_trylock((z)->uz_lockptr)
  375 #define ZONE_UNLOCK(z)  mtx_unlock((z)->uz_lockptr)
  376 #define ZONE_LOCK_FINI(z)       mtx_destroy(&(z)->uz_lock)
  377 
  378 /*
  379  * Find a slab within a hash table.  This is used for OFFPAGE zones to lookup
  380  * the slab structure.
  381  *
  382  * Arguments:
  383  *      hash  The hash table to search.
  384  *      data  The base page of the item.
  385  *
  386  * Returns:
  387  *      A pointer to a slab if successful, else NULL.
  388  */
  389 static __inline uma_slab_t
  390 hash_sfind(struct uma_hash *hash, uint8_t *data)
  391 {
  392         uma_slab_t slab;
  393         int hval;
  394 
  395         hval = UMA_HASH(hash, data);
  396 
  397         SLIST_FOREACH(slab, &hash->uh_slab_hash[hval], us_hlink) {
  398                 if ((uint8_t *)slab->us_data == data)
  399                         return (slab);
  400         }
  401         return (NULL);
  402 }
  403 
  404 static __inline uma_slab_t
  405 vtoslab(vm_offset_t va)
  406 {
  407         vm_page_t p;
  408 
  409         p = PHYS_TO_VM_PAGE(pmap_kextract(va));
  410         return ((uma_slab_t)p->plinks.s.pv);
  411 }
  412 
  413 static __inline void
  414 vsetslab(vm_offset_t va, uma_slab_t slab)
  415 {
  416         vm_page_t p;
  417 
  418         p = PHYS_TO_VM_PAGE(pmap_kextract(va));
  419         p->plinks.s.pv = slab;
  420 }
  421 
  422 /*
  423  * The following two functions may be defined by architecture specific code
  424  * if they can provide more effecient allocation functions.  This is useful
  425  * for using direct mapped addresses.
  426  */
  427 void *uma_small_alloc(uma_zone_t zone, int bytes, uint8_t *pflag, int wait);
  428 void uma_small_free(void *mem, int size, uint8_t flags);
  429 #endif /* _KERNEL */
  430 
  431 #endif /* VM_UMA_INT_H */

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