2 .\" Copyright (c) 2001 Dag-Erling Coïdan Smørgrav
3 .\" All rights reserved.
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48 .Fa "char *name" "int size"
49 .Fa "uma_ctor ctor" "uma_dtor dtor" "uma_init uminit" "uma_fini fini"
50 .Fa "int align" "u_int16_t flags"
53 .Fn uma_zalloc "uma_zone_t zone" "int flags"
55 .Fn uma_zalloc_arg "uma_zone_t zone" "void *arg" "int flags"
57 .Fn uma_zfree "uma_zone_t zone" "void *item"
59 .Fn uma_zfree_arg "uma_zone_t zone" "void *item" "void *arg"
61 .Fn uma_zdestroy "uma_zone_t zone"
63 .Fn uma_zone_set_max "uma_zone_t zone" "int nitems"
65 .Fn uma_zone_get_max "uma_zone_t zone"
67 .Fn uma_zone_get_cur "uma_zone_t zone"
69 The zone allocator provides an efficient interface for managing
70 dynamically-sized collections of items of similar size.
71 The zone allocator can work with preallocated zones as well as with
72 runtime-allocated ones, and is therefore available much earlier in the
73 boot process than other memory management routines.
75 A zone is an extensible collection of items of identical size.
76 The zone allocator keeps track of which items are in use and which
77 are not, and provides functions for allocating items from the zone and
78 for releasing them back (which makes them available for later use).
80 After the first allocation of an item,
81 it will have been cleared to zeroes, however subsequent allocations
82 will retain the contents as of the last free.
86 function creates a new zone from which items may then be allocated from.
89 argument is a text name of the zone for debugging and stats; this memory
90 should not be freed until the zone has been deallocated.
96 arguments are callback functions that are called by
97 the uma subsystem at the time of the call to
102 Their purpose is to provide hooks for initializing or
103 destroying things that need to be done at the time of the allocation
104 or release of a resource.
110 might be to adjust a global count of the number of objects allocated.
116 arguments are used to optimize the allocation of
117 objects from the zone.
118 They are called by the uma subsystem whenever
119 it needs to allocate or free several items to satisfy requests or memory
125 callbacks might be to
126 initialize and destroy mutexes contained within the object.
128 allow one to re-use already initialized mutexes when an object is returned
129 from the uma subsystem's object cache.
130 They are not called on each call to
134 but rather in a batch mode on several objects.
136 To allocate an item from a zone, simply call
138 with a pointer to that zone
141 argument to selected flags as documented in
143 It will return a pointer to an item if successful,
146 in the rare case where all items in the zone are in use and the
147 allocator is unable to grow the zone
152 Items are released back to the zone from which they were allocated by
155 with a pointer to the zone and a pointer to the item.
169 specify an argument for the
173 functions, respectively.
177 can be destroyed using
179 freeing all memory that was allocated for the zone.
180 All items allocated from the zone with
182 must have been freed with
188 function limits the number of items
189 .Pq and therefore memory
190 that can be allocated to
194 argument specifies the requested upper limit number of items.
195 The effective limit is returned to the caller, as it may end up being higher
196 than requested due to the implementation rounding up to ensure all memory pages
197 allocated to the zone are utilised to capacity.
198 The limit applies to the total number of items in the zone, which includes
199 allocated items, free items and free items in the per-cpu caches.
200 On systems with more than one CPU it may not be possible to allocate
201 the specified number of items even when there is no shortage of memory,
202 because all of the remaining free items may be in the caches of the
203 other CPUs when the limit is hit.
207 function returns the effective upper limit number of items for a zone.
211 function returns the approximate current occupancy of the zone.
212 The returned value is approximate because appropriate synchronisation to
213 determine an exact value is not performed by the implementation.
214 This ensures low overhead at the expense of potentially stale data being used
219 function returns a pointer to an item, or
221 if the zone ran out of unused items and the allocator was unable to
226 The zone allocator first appeared in
228 It was radically changed in
230 to function as a slab allocator.
233 The zone allocator was written by
235 The zone allocator was rewritten in large parts by
236 .An Jeff Roberson Aq jeff@FreeBSD.org
237 to function as a slab allocator.
239 This manual page was written by
240 .An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org .
242 .An Jeroen Ruigrok van der Werven Aq asmodai@FreeBSD.org .