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

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2002-2005, 2009, 2013 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.
     *
     * $FreeBSD$
     *
     */
    
    #include <sys/_bitset.h>
    #include <sys/_domainset.h>
    #include <sys/_task.h>
    
    /* 
     * This file includes definitions, structures, prototypes, and inlines that
     * should not be used outside of the actual implementation of UMA.
     */
    
    /* 
     * The brief summary;  Zones describe unique allocation types.  Zones are
     * organized into per-CPU caches which are filled by buckets.  Buckets are
     * organized according to memory domains.  Buckets are filled from kegs which
     * are also organized according to memory domains.  Kegs describe a unique
     * allocation type, backend memory provider, and layout.  Kegs are associated
     * with one or more zones and zones reference one or more kegs.  Kegs provide
     * slabs which are virtually contiguous collections of pages.  Each slab is
     * broken down int one or more items that will satisfy an individual allocation.
     *
     * Allocation is satisfied in the following order:
     * 1) Per-CPU cache
     * 2) Per-domain cache of buckets
     * 3) Slab from any of N kegs
     * 4) Backend page provider
     *
     * More detail on individual objects is contained below:
     *
     * 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.
     *
     * Keg slab lists are organized by memory domain to support NUMA allocation
     * policies.  By default allocations are spread across domains to reduce the
     * potential for hotspots.  Special keg creation flags may be specified to
     * prefer location allocation.  However there is no strict enforcement as frees
     * may happen on any CPU and these are returned to the CPU-local cache
     * regardless of the originating domain.
     *  
     * 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 bitmask.  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.  
     *
     * 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 */
   
   /* Max waste percentage before going to off page slab management */
   #define UMA_MAX_WASTE   10
   
   /*
    * Size of memory in a not offpage slab available for actual items.
    */
   #define UMA_SLAB_SPACE  (UMA_SLAB_SIZE - sizeof(struct uma_slab))
   
   /*
    * 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.
    */
   
   #define UMA_HASH(h, s) ((((uintptr_t)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 */
           u_int           uh_hashsize;    /* Current size of the hash table */
           u_int           uh_hashmask;    /* Mask used during hashing */
   };
   
   /*
    * align field or structure to cache line
    */
   #if defined(__amd64__) || defined(__powerpc64__)
   #define UMA_ALIGN       __aligned(128)
   #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 items in bucket. */
           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 */
           uint64_t        uc_allocs;      /* Count of allocations */
           uint64_t        uc_frees;       /* Count of frees */
   } UMA_ALIGN;
   
   typedef struct uma_cache * uma_cache_t;
   
   /*
    * Per-domain memory list.  Embedded in the kegs.
    */
   struct uma_domain {
           LIST_HEAD(,uma_slab)    ud_part_slab;   /* partially allocated slabs */
           LIST_HEAD(,uma_slab)    ud_free_slab;   /* empty slab list */
           LIST_HEAD(,uma_slab)    ud_full_slab;   /* full slabs */
   };
   
   typedef struct uma_domain * uma_domain_t;
   
   /*
    * Keg management structure
    *
    * TODO: Optimize for cache line size
    *
    */
   struct uma_keg {
           struct mtx      uk_lock;        /* Lock for the keg */
           struct uma_hash uk_hash;
           LIST_HEAD(,uma_zone)    uk_zones;       /* Keg's zones */
   
           struct domainset_ref uk_dr;     /* Domain selection policy. */
           uint32_t        uk_align;       /* Alignment mask */
           uint32_t        uk_pages;       /* Total page count */
           uint32_t        uk_free;        /* Count of items free in slabs */
           uint32_t        uk_reserve;     /* Number of reserved items. */
           uint32_t        uk_size;        /* Requested size of each item */
           uint32_t        uk_rsize;       /* Real size of each item */
           uint32_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 */
   
           u_long          uk_offset;      /* Next free offset from base KVA */
           vm_offset_t     uk_kva;         /* Zone base KVA */
           uma_zone_t      uk_slabzone;    /* Slab zone backing us, if OFFPAGE */
   
           uint32_t        uk_pgoff;       /* Offset to uma_slab struct */
           uint16_t        uk_ppera;       /* pages per allocation from backend */
           uint16_t        uk_ipers;       /* Items per slab */
           uint32_t        uk_flags;       /* Internal flags */
   
           /* Least used fields go to the last cache line. */
           const char      *uk_name;               /* Name of creating zone. */
           LIST_ENTRY(uma_keg)     uk_link;        /* List of all kegs */
   
           /* Must be last, variable sized. */
           struct uma_domain       uk_domain[];    /* Keg's slab lists. */
   };
   typedef struct uma_keg  * uma_keg_t;
   
   /*
    * Free bits per-slab.
    */
   #define SLAB_SETSIZE    (PAGE_SIZE / UMA_SMALLEST_UNIT)
   BITSET_DEFINE(slabbits, SLAB_SETSIZE);
   
   /*
    * The slab structure manages a single contiguous allocation from backing
    * store and subdivides it into individually allocatable items.
    */
   struct uma_slab {
           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 */
           uint8_t         *us_data;               /* First item */
           struct slabbits us_free;                /* Free bitmask. */
   #ifdef INVARIANTS
           struct slabbits us_debugfree;           /* Debug bitmask. */
   #endif
           uint16_t        us_freecount;           /* How many are free? */
           uint8_t         us_flags;               /* Page flags see uma.h */
           uint8_t         us_domain;              /* Backing NUMA domain. */
   };
   
   #define us_link us_type._us_link
   #define us_size us_type._us_size
   
   #if MAXMEMDOM >= 255
   #error "Slab domain type insufficient"
   #endif
   
   typedef struct uma_slab * uma_slab_t;
   typedef uma_slab_t (*uma_slaballoc)(uma_zone_t, uma_keg_t, int, int);
   
   struct uma_klink {
           LIST_ENTRY(uma_klink)   kl_link;
           uma_keg_t               kl_keg;
   };
   typedef struct uma_klink *uma_klink_t;
   
   struct uma_zone_domain {
           LIST_HEAD(,uma_bucket)  uzd_buckets;    /* full buckets */
           long            uzd_nitems;     /* total item count */
           long            uzd_imax;       /* maximum item count this period */
           long            uzd_imin;       /* minimum item count this period */
           long            uzd_wss;        /* working set size estimate */
   };
   
   typedef struct uma_zone_domain * uma_zone_domain_t;
   
   /*
    * Zone management structure 
    *
    * TODO: Optimize for cache line size
    *
    */
   struct uma_zone {
           /* Offset 0, used in alloc/free fast/medium fast path and const. */
           struct mtx      *uz_lockptr;
           const char      *uz_name;       /* Text name of the zone */
           struct uma_zone_domain  *uz_domain;     /* per-domain buckets */
           uint32_t        uz_flags;       /* Flags inherited from kegs */
           uint32_t        uz_size;        /* Size inherited from kegs */
           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;        /* Finalizer for each item. */
   
           /* Offset 64, used in bucket replenish. */
           uma_import      uz_import;      /* Import new memory to cache. */
           uma_release     uz_release;     /* Release memory from cache. */
           void            *uz_arg;        /* Import/release argument. */
           uma_slaballoc   uz_slab;        /* Allocate a slab from the backend. */
           uint16_t        uz_count;       /* Amount of items in full bucket */
           uint16_t        uz_count_min;   /* Minimal amount of items there */
           /* 32bit pad on 64bit. */
           LIST_ENTRY(uma_zone)    uz_link;        /* List of all zones in keg */
           LIST_HEAD(,uma_klink)   uz_kegs;        /* List of kegs. */
   
           /* Offset 128 Rare. */
           /*
            * The lock is placed here to avoid adjacent line prefetcher
            * in fast paths and to take up space near infrequently accessed
            * members to reduce alignment overhead.
            */
           struct mtx      uz_lock;        /* Lock for the zone */
           struct uma_klink        uz_klink;       /* klink for first keg. */
           /* The next two fields are used to print a rate-limited warnings. */
           const char      *uz_warning;    /* Warning to print on failure */
           struct timeval  uz_ratecheck;   /* Warnings rate-limiting */
           struct task     uz_maxaction;   /* Task to run when at limit */
   
           /* 16 bytes of pad. */
   
           /* Offset 256, atomic stats. */
           volatile u_long uz_allocs UMA_ALIGN; /* Total number of allocations */
           volatile u_long uz_fails;       /* Total number of alloc failures */
           volatile u_long uz_frees;       /* Total number of frees */
           uint64_t        uz_sleeps;      /* Total number of alloc sleeps */
   
           /*
            * 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[]; /* Per cpu caches */
   
           /* uz_domain follows here. */
   };
   
   /*
    * These flags must not overlap with the UMA_ZONE flags specified in uma.h.
    */
   #define UMA_ZFLAG_MULTI         0x04000000      /* Multiple kegs in the zone. */
   #define UMA_ZFLAG_DRAINING      0x08000000      /* Running zone_drain. */
   #define UMA_ZFLAG_BUCKET        0x10000000      /* Bucket zone. */
   #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)
   
   static inline uma_keg_t
   zone_first_keg(uma_zone_t zone)
   {
           uma_klink_t klink;
   
           klink = LIST_FIRST(&zone->uz_kegs);
           return (klink != NULL) ? klink->kl_keg : NULL;
   }
   
   #undef UMA_ALIGN
   
   #ifdef _KERNEL
   /* Internal prototypes */
   static __inline uma_slab_t hash_sfind(struct uma_hash *hash, uint8_t *data);
   void *uma_large_malloc(vm_size_t size, int wait);
   void *uma_large_malloc_domain(vm_size_t size, int domain, 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_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(z)    mtx_lock((z)->uz_lockptr)
   #define ZONE_TRYLOCK(z) mtx_trylock((z)->uz_lockptr)
   #define ZONE_UNLOCK(z)  mtx_unlock((z)->uz_lockptr)
   #define ZONE_LOCK_FINI(z)       mtx_destroy(&(z)->uz_lock)
   #define ZONE_LOCK_ASSERT(z)     mtx_assert((z)->uz_lockptr, MA_OWNED)
   
   /*
    * 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, uint8_t *data)
   {
           uma_slab_t slab;
           u_int hval;
   
           hval = UMA_HASH(hash, data);
   
           SLIST_FOREACH(slab, &hash->uh_slab_hash[hval], us_hlink) {
                   if ((uint8_t *)slab->us_data == data)
                           return (slab);
           }
           return (NULL);
   }
   
   static __inline uma_slab_t
   vtoslab(vm_offset_t va)
   {
           vm_page_t p;
   
           p = PHYS_TO_VM_PAGE(pmap_kextract(va));
           return ((uma_slab_t)p->plinks.s.pv);
   }
   
   static __inline void
   vsetslab(vm_offset_t va, uma_slab_t slab)
   {
           vm_page_t p;
   
           p = PHYS_TO_VM_PAGE(pmap_kextract(va));
           p->plinks.s.pv = slab;
   }
   
   /*
    * The following two functions may be defined by architecture specific code
    * if they can provide more efficient allocation functions.  This is useful
    * for using direct mapped addresses.
    */
   void *uma_small_alloc(uma_zone_t zone, vm_size_t bytes, int domain,
       uint8_t *pflag, int wait);
   void uma_small_free(void *mem, vm_size_t size, uint8_t flags);
   
   /* Set a global soft limit on UMA managed memory. */
   void uma_set_limit(unsigned long limit);
   #endif /* _KERNEL */
   
   #endif /* VM_UMA_INT_H */

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