2 .\" Copyright (c) 2001 Dag-Erling Coïdan Smørgrav
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42 .Nm uma_zone_set_warning
50 .Fa "char *name" "int size"
51 .Fa "uma_ctor ctor" "uma_dtor dtor" "uma_init uminit" "uma_fini fini"
52 .Fa "int align" "uint16_t flags"
55 .Fn uma_zalloc "uma_zone_t zone" "int flags"
57 .Fn uma_zalloc_arg "uma_zone_t zone" "void *arg" "int flags"
59 .Fn uma_zfree "uma_zone_t zone" "void *item"
61 .Fn uma_zfree_arg "uma_zone_t zone" "void *item" "void *arg"
63 .Fn uma_find_refcnt "uma_zone_t zone" "void *item"
65 .Fn uma_zdestroy "uma_zone_t zone"
67 .Fn uma_zone_set_max "uma_zone_t zone" "int nitems"
69 .Fn uma_zone_get_max "uma_zone_t zone"
71 .Fn uma_zone_get_cur "uma_zone_t zone"
73 .Fn uma_zone_set_warning "uma_zone_t zone" "const char *warning"
75 .Fn SYSCTL_UMA_MAX parent nbr name access zone descr
76 .Fn SYSCTL_ADD_UMA_MAX ctx parent nbr name access zone descr
77 .Fn SYSCTL_UMA_CUR parent nbr name access zone descr
78 .Fn SYSCTL_ADD_UMA_CUR ctx parent nbr name access zone descr
80 The zone allocator provides an efficient interface for managing
81 dynamically-sized collections of items of similar size.
82 The zone allocator can work with preallocated zones as well as with
83 runtime-allocated ones, and is therefore available much earlier in the
84 boot process than other memory management routines.
86 A zone is an extensible collection of items of identical size.
87 The zone allocator keeps track of which items are in use and which
88 are not, and provides functions for allocating items from the zone and
89 for releasing them back (which makes them available for later use).
91 After the first allocation of an item,
92 it will have been cleared to zeroes, however subsequent allocations
93 will retain the contents as of the last free.
97 function creates a new zone from which items may then be allocated from.
100 argument is a text name of the zone for debugging and stats; this memory
101 should not be freed until the zone has been deallocated.
107 arguments are callback functions that are called by
108 the uma subsystem at the time of the call to
113 Their purpose is to provide hooks for initializing or
114 destroying things that need to be done at the time of the allocation
115 or release of a resource.
121 might be to adjust a global count of the number of objects allocated.
127 arguments are used to optimize the allocation of
128 objects from the zone.
129 They are called by the uma subsystem whenever
130 it needs to allocate or free several items to satisfy requests or memory
136 callbacks might be to
137 initialize and destroy mutexes contained within the object.
139 allow one to re-use already initialized mutexes when an object is returned
140 from the uma subsystem's object cache.
141 They are not called on each call to
145 but rather in a batch mode on several objects.
151 is a subset of the following flags:
152 .Bl -tag -width "foo"
153 .It Dv UMA_ZONE_NOFREE
154 Slabs of the zone are never returned back to VM.
155 .It Dv UMA_ZONE_REFCNT
156 Each item in the zone would have internal reference counter associated with it.
158 .Fn uma_find_refcnt .
159 .It Dv UMA_ZONE_NODUMP
160 Pages belonging to the zone will not be included into mini-dumps.
162 An allocation from zone would have
164 shadow copies, that are privately assigned to CPUs.
165 A CPU can address its private copy using base allocation address plus
166 multiple of current CPU id and
167 .Fn sizeof "struct pcpu" :
168 .Bd -literal -offset indent
169 foo_zone = uma_zcreate(..., UMA_ZONE_PCPU);
171 foo_base = uma_zalloc(foo_zone, ...);
174 foo_pcpu = (foo_t *)zpcpu_get(foo_base);
175 /* do something with foo_pcpu */
178 .It Dv UMA_ZONE_OFFPAGE
179 By default book-keeping of items within a slab is done in the slab page itself.
180 This flag explicitly tells subsystem that book-keeping structure should be
181 allocated separately from special internal zone.
182 This flag requires either
186 since subsystem requires a mechanism to find a book-keeping structure
187 to an item beeing freed.
188 The subsystem may choose to prefer offpage book-keeping for certain zones
190 .It Dv UMA_ZONE_ZINIT
191 The zone will have its
193 method set to internal method that initializes a new allocated slab
201 flag would not return zeroed memory on every
204 The zone should use an internal hash table to find slab book-keeping
205 structure where an allocation being freed belongs to.
206 .It Dv UMA_ZONE_VTOSLAB
207 The zone should use special field of
209 to find slab book-keeping structure where an allocation being freed belongs to.
210 .It Dv UMA_ZONE_MALLOC
215 The zone is for the VM subsystem.
218 To allocate an item from a zone, simply call
220 with a pointer to that zone
223 argument to selected flags as documented in
225 It will return a pointer to an item if successful,
228 in the rare case where all items in the zone are in use and the
229 allocator is unable to grow the zone
234 Items are released back to the zone from which they were allocated by
237 with a pointer to the zone and a pointer to the item.
251 specify an argument for the
255 functions, respectively.
257 If zone was created with
259 flag, then pointer to reference counter for an item can be retrieved with
266 can be destroyed using
268 freeing all memory that was allocated for the zone.
269 All items allocated from the zone with
271 must have been freed with
277 function limits the number of items
278 .Pq and therefore memory
279 that can be allocated to
283 argument specifies the requested upper limit number of items.
284 The effective limit is returned to the caller, as it may end up being higher
285 than requested due to the implementation rounding up to ensure all memory pages
286 allocated to the zone are utilised to capacity.
287 The limit applies to the total number of items in the zone, which includes
288 allocated items, free items and free items in the per-cpu caches.
289 On systems with more than one CPU it may not be possible to allocate
290 the specified number of items even when there is no shortage of memory,
291 because all of the remaining free items may be in the caches of the
292 other CPUs when the limit is hit.
296 function returns the effective upper limit number of items for a zone.
300 function returns the approximate current occupancy of the zone.
301 The returned value is approximate because appropriate synchronisation to
302 determine an exact value is not performed by the implementation.
303 This ensures low overhead at the expense of potentially stale data being used
307 .Fn uma_zone_set_warning
308 function sets a warning that will be printed on the system console when the
309 given zone becomes full and fails to allocate an item.
310 The warning will be printed not often than every five minutes.
311 Warnings can be turned off globally by setting the
317 .Fn SYSCTL_UMA_MAX parent nbr name access zone descr
318 macro declares a static
320 oid that exports the effective upper limit number of items for a zone.
323 argument should be a pointer to
325 A read of the oid returns value obtained through
326 .Fn uma_zone_get_max .
327 A write to the oid sets new value via
328 .Fn uma_zone_set_max .
330 .Fn SYSCTL_ADD_UMA_MAX ctx parent nbr name access zone descr
331 macro is provided to create this type of oid dynamically.
334 .Fn SYSCTL_UMA_CUR parent nbr name access zone descr
335 macro declares a static read only
337 oid that exports the approximate current occupancy of the zone.
340 argument should be a pointer to
342 A read of the oid returns value obtained through
343 .Fn uma_zone_get_cur .
345 .Fn SYSCTL_ADD_UMA_CUR ctx parent nbr name zone descr
346 macro is provided to create this type of oid dynamically.
350 function returns a pointer to an item, or
352 if the zone ran out of unused items
359 The zone allocator first appeared in
361 It was radically changed in
363 to function as a slab allocator.
366 The zone allocator was written by
368 The zone allocator was rewritten in large parts by
369 .An Jeff Roberson Aq jeff@FreeBSD.org
370 to function as a slab allocator.
372 This manual page was written by
373 .An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org .
375 .An Jeroen Ruigrok van der Werven Aq asmodai@FreeBSD.org .