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  12 .\" Copyright 2017, Richard Lowe.
  13 .\"
  14 .Dd Jan 18, 2017
  15 .Dt VMEM_CREATE 9F
  16 .Os
  17 .Sh NAME
  18 .Nm vmem_create ,
  19 .Nm vmem_xcreate ,
  20 .Nm vmem_destroy
  21 .Nd create and destroy vmem arenas
  22 .Sh SYNOPSIS
  23 .In sys/vmem.h
  24 .Vt "typedef struct vmem vmem_t;"
  25 .Vt "typedef void *(vmem_alloc_t)(vmem_t *, size_t, int);"
  26 .Vt "typedef void (vmem_free_t)(vmem_t *, void *, size_t);"
  27 .Vt "typedef void *(vmem_ximport_t)(vmem_t *, size_t *, size_t, int);"
  28 .Ft vmem_t *
  29 .Fo vmem_create
  30 .Fa "const char *name"
  31 .Fa "void *base"
  32 .Fa "size_t size"
  33 .Fa "size_t quantum"
  34 .Fa "vmem_alloc_t *afunc"
  35 .Fa "vmem_free_t *ffunc"
  36 .Fa "vmem_t *source"
  37 .Fa "size_t qcache_max"
  38 .Fa "int vmflag"
  39 .Fc
  40 .Ft vmem_t *
  41 .Fo vmem_xcreate
  42 .Fa "const char *name"
  43 .Fa "void *base"
  44 .Fa "size_t size"
  45 .Fa "size_t quantum"
  46 .Fa "vmem_ximport_t *afunc"
  47 .Fa "vmem_free_t *ffunc"
  48 .Fa "vmem_t *source"
  49 .Fa "size_t qcache_max"
  50 .Fa "int vmflag"
  51 .Fc
  52 .Ft void
  53 .Fo vmem_destroy
  54 .Fa "vmem_t *vmp"
  55 .Fc
  56 .Sh INTERFACE LEVEL
  57 illumos DDI specific
  58 .Sh PARAMETERS
  59 .Bl -tag -width Ds
  60 .It Fa name
  61 A character string giving a name to the vmem
  62 arena to be created.
  63 .It Fa base
  64 An address indicating the lowest possible value in the arena.
  65 .It Fa size
  66 The size of the arena to create.
  67 .It Fa quantum
  68 The arena's
  69 .Dq quantum .
  70 The granularity of the arena.  The amount allocated at minimum by each
  71 request.  Must be a power of 2.
  72 .It Fa afunc
  73 A function which is called to import new spans from
  74 .Fa source ,
  75 which may be
  76 .Dv NULL
  77 if this arena does not import from another.
  78 When calling
  79 .Fn vmem_create ,
  80 .Fa afunc
  81 is a
  82 .Vt vmem_alloc_t ,
  83 a function taking three parameters and returning a pointer to
  84 .Vt void
  85 (the imported space):
  86 .Bl -tag -width Ds
  87 .It Fa "vmem_t *"
  88 The source arena from which we'll import.  The
  89 .Fa source
  90 argument to
  91 .Fn vmem_create .
  92 .It Fa size_t
  93 The size to import.
  94 .It Fa int
  95 The
  96 .Fa vmflag
  97 argument used for the import.
  98 .El
  99 .Pp
 100 When calling
 101 .Fn vmem_xcreate ,
 102 .Fa afunc
 103 is a
 104 .Vt vmem_ximport_t ,
 105 a function taking four parameters and returning a pointer to
 106 .Vt void
 107 (the imported space):
 108 .Bl -tag -width Ds
 109 .It Fa "vmem_t *"
 110 The source arena from which we'll import.  The
 111 .Fa source
 112 argument to
 113 .Fn vmem_xcreate .
 114 .It Fa "size_t *"
 115 The size of the import.
 116 .Fa afunc
 117 may
 118 .Em increase
 119 this size if that is desirable, but must never decrease it.
 120 .It Fa size_t
 121 The desired alignment of the imported space.
 122 .It Fa int
 123 The
 124 .Fa vmflag
 125 argument used for the import.
 126 .El
 127 .It Fa ffunc
 128 A function which is called to return spans to
 129 .Fa source ,
 130 which may be
 131 .Dv NULL
 132 if this arena does not import from another.
 133 This is a
 134 .Vt vmem_free_t ,
 135 a function taking three parameters and returning void:
 136 .Bl -tag -width Ds
 137 .It Fa "vmem_t"
 138 The arena to which space is being returned.  The
 139 .Fa source
 140 argument to
 141 .Fn vmem_create
 142 or
 143 .Fn vmem_xcreate .
 144 .It Fa "void *"
 145 The span being returned to the source arena.
 146 .It Fa "size_t"
 147 The size of the span being returned to the source arena.
 148 .El
 149 .It Fa source
 150 An arena from which this arena will import,
 151 which may be
 152 .Dv NULL
 153 if this arena does not import from another.
 154 .It Fa qcache_max
 155 Each arena offers caching of integer multiples of
 156 .Fa quantum
 157 up to
 158 .Fa qcache_max ,
 159 which may be 0.
 160 .It Fa vmflag
 161 A bitmask of flags indicating the characteristics of this arena.
 162 .Bl -tag -width Ds
 163 .It Dv VMC_IDENTIFIER
 164 The arena represents arbitrary integer identifiers, rather than virtual
 165 memory.
 166 .El
 167 .It Fa vmp
 168 A pointer to the vmem arena to be destroyed.
 169 .El
 170 .Sh DESCRIPTION
 171 A
 172 .Em vmem arena
 173 is a section of an arbitrary address space (a range of integer addresses).
 174 This commonly represents virtual memory, but can in fact be an arbitrary set
 175 of integers. The
 176 .Dv VMC_IDENTIFIER
 177 flag set at arena creation time differentiates between these two cases.
 178 .Pp
 179 The
 180 .Fa afunc ,
 181 .Fa ffunc , and
 182 .Fa source
 183 arguments combine to support a hierarchical structure of arenas, each
 184 importing from a single parent (the
 185 .Fa source ) .
 186 The
 187 .Fn vmem_create
 188 and
 189 .Fn vmem_xcreate
 190 functions differ in that the latter provides an interface for
 191 .Fa afunc
 192 to alter the size of the span imported from
 193 .Fa source .
 194 It is only legal to
 195 .Em increase
 196 this size.
 197 .Sh CONTEXT
 198 These functions can be called from user or kernel context.
 199 .Sh RETURN VALUES
 200 Upon successful completion the
 201 .Fn vmem_create
 202 and
 203 .Fn vmem_xcreate
 204 functions return a pointer to a vmem arena.  Otherwise,
 205 .Dv NULL
 206 is returned to indicate the arena could not be created.
 207 .Sh SEE ALSO
 208 .Xr vmem 9 ,
 209 .Xr vmem_add 9F ,
 210 .Xr vmem_alloc 9F