2 .\" Copyright (c) 2001 Dag-Erling Coïdan Smørgrav
3 .\" All rights reserved.
5 .\" Redistribution and use in source and binary forms, with or without
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14 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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19 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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26 .\" $FreeBSD: src/share/man/man9/zone.9,v 1.9.2.4 2002/05/02 20:01:29 asmodai Exp $
44 .Fn zbootinit "vm_zone_t z" "char *name" "int size" "void *item" "int nitems"
46 .Fn zinitna "vm_zone_t z" "struct vm_object *obj" "char *name" "int size" "int nentries" "int flags" "int zalloc"
48 .Fn zinit "char *name" "int size" "int nentries" "int flags" "int zalloc"
50 .Fn zdestroy "vm_zone_t z"
52 .Fn zalloc "vm_zone_t z"
54 .Fn zfree "vm_zone_t z" "void *item"
56 The zone allocator is deprecated.
61 The zone allocator provides an efficient interface for managing
62 dynamically-sized collections of items of similar size.
63 The zone allocator can work with preallocated zones as well as with
64 runtime-allocated ones, and is therefore available much earlier in the
65 boot process than other memory management routines.
67 A zone is an extensible collection of items of identical size.
68 The zone allocator keeps track of which items are in use and which
69 are not, and provides functions for allocating items from the zone and
70 for releasing them back (which makes them available for later use).
72 The zone allocator stores state information inside the items proper
73 while they are not allocated,
74 so structures that will be managed by the zone allocator
75 and wish to use the type stable property of zones by leaving some fields
76 pre-filled between allocations, must reserve
77 two pointers at the very beginning for internal use by the zone
78 allocator, as follows:
81 struct my_item *z_rsvd1;
82 struct my_item *z_rsvd2;
83 /* rest of structure */
87 Alternatively they should assume those entries corrupted
88 after each allocation.
89 After the first allocation of an item,
90 it will have been cleared to zeroes, however subsequent allocations
91 will retain the contents as of the last free, with the exception of the
92 fields mentioned above.
94 Zones are created in one of two fashions, depending how far along the
97 If the VM system is fully initialized, a dynamically allocated zone can
102 argument should be a pointer to a short, descriptive name for the
103 zone; it is used for statistics and debugging purposes.
108 are the size of the items held by the zone and the initial size (in
109 items) of the zone, respectively.
112 argument should have the
114 bit set if there is a chance that items may be allocated from the zone in
115 interrupt context; note that in this case, the zone will never grow
121 argument should have the
123 bit set if the zone is to be destroyed with
127 indicates the number of VM pages by which the zone should grow every
130 If the VM system is not yet fully initialized, the zone allocator
131 cannot dynamically allocate VM pages from which to dole out items, so
132 the caller needs to provide a static pool of items.
133 In this case, the initialization is done in two stages: first,
135 is called before first use of the zone; later, when the VM system is
136 up, the initialization of the zone is completed by calling
139 The first argument to
141 is a pointer to a static
144 The second and third are the name of the zone and the size of the
146 The fourth argument is a pointer to a static array of items from which
147 the zone allocator will draw until the zone is fully initialized.
150 argument is the number of items in the array.
156 with the addition of a pointer to the zone to initialize, and a
158 .Vt "struct vm_object"
159 from which to allocate pages in the
163 To release all the memory allocated for a zone, call
165 Only zones created with
169 flag can be destroyed.
171 To allocate an item from a zone, simply call
173 with a pointer to that zone; it will return a pointer to an item, or
175 in the rare case where all items in the zone are in use and the
176 allocator is unable to grow the zone.
178 Items are released back to the zone from which they were allocated by
181 with a pointer to the zone and a pointer to the item.
183 The zone functions are not SMP-safe.
184 The MP lock must be held while calling them.
188 function returns 1 on success and 0 on failure; the only failure case
189 is inability to preallocate address space for an interrupt-safe zone.
193 function returns a pointer to a fully initialized
194 .Vt "struct vm_zone" ,
203 flag was specified and
205 failed to preallocate address space.
209 function returns a pointer to an item, or
211 if the zone ran out of unused items and the allocator was unable to
216 The zone allocator first appeared in
220 The zone allocator was written by
223 This manual page was written by
224 .An Dag-Erling Co\(:idan Sm\(/orgrav Aq Mt des@FreeBSD.org .