2 .\" Copyright (c) 2001 Dag-Erling Coïdan Smørgrav
3 .\" All rights reserved.
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44 .Fa "char *name" "int size"
45 .Fa "uma_ctor ctor" "uma_dtor dtor" "uma_init uminit" "uma_fini fini"
46 .Fa "int align" "u_int16_t flags"
49 .Fn uma_zalloc "uma_zone_t zone" "int flags"
51 .Fn uma_zfree "uma_zone_t zone" "void *item"
53 .Fn uma_zdestroy "uma_zone_t zone"
55 .Fn uma_zone_set_max "uma_zone_t zone" "int nitems"
57 The zone allocator provides an efficient interface for managing
58 dynamically-sized collections of items of similar size.
59 The zone allocator can work with preallocated zones as well as with
60 runtime-allocated ones, and is therefore available much earlier in the
61 boot process than other memory management routines.
63 A zone is an extensible collection of items of identical size.
64 The zone allocator keeps track of which items are in use and which
65 are not, and provides functions for allocating items from the zone and
66 for releasing them back (which makes them available for later use).
68 After the first allocation of an item,
69 it will have been cleared to zeroes, however subsequent allocations
70 will retain the contents as of the last free.
74 function creates a new zone from which items may then be allocated from.
77 argument is a text name of the zone for debugging and stats; this memory
78 should not be freed until the zone has been deallocated.
84 arguments are callback functions that are called by
85 the uma subsystem at the time of the call to
90 Their purpose is to provide hooks for initializing or
91 destroying things that need to be done at the time of the allocation
92 or release of a resource.
98 might be to adjust a global count of the number of objects allocated.
104 arguments are used to optimize the allocation of
105 objects from the zone.
106 They are called by the uma subsystem whenever
107 it needs to allocate or free several items to satisfy requests or memory
113 callbacks might be to
114 initialize and destroy mutexes contained within the object.
116 allow one to re-use already initialized mutexes when an object is returned
117 from the uma subsystem's object cache.
118 They are not called on each call to
122 but rather in a batch mode on several objects.
124 To allocate an item from a zone, simply call
126 with a pointer to that zone
129 argument to selected flags as documented in
131 It will return a pointer to an item if successful,
134 in the rare case where all items in the zone are in use and the
135 allocator is unable to grow the zone
140 Items are released back to the zone from which they were allocated by
143 with a pointer to the zone and a pointer to the item.
147 can be destroyed using
149 freeing all memory that was allocated for the zone.
150 All items allocated from the zone with
152 must have been freed with
158 is to limit the maximum amount of memory that the system can dedicated
159 toward the zone specified by the
164 argument gives the upper limit of items in the zone.
165 This limits the total number of items in the zone which includes:
166 allocated items, free items and free items in the per-cpu caches.
167 On systems with more than one CPU it may not be possible to allocate
168 the specified number of items even when there is no shortage of memory,
169 because all of the remaining free items may be in the caches of the
170 other CPUs when the limit is hit.
174 function returns a pointer to an item, or
176 if the zone ran out of unused items and the allocator was unable to
181 The zone allocator first appeared in
183 It was radically changed in
185 to function as a slab allocator.
188 The zone allocator was written by
190 The zone allocator was rewritten in large parts by
191 .An Jeff Roberson Aq jeff@FreeBSD.org
192 to function as a slab allocator.
194 This manual page was written by
195 .An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org .
197 .An Jeroen Ruigrok van der Werven Aq asmodai@FreeBSD.org .