2 .\" Copyright (c) 2001 Dag-Erling Coïdan Smørgrav
3 .\" All rights reserved.
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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 $
27 .\" $DragonFly: src/share/man/man9/zone.9,v 1.7 2008/01/22 19:17:38 swildner Exp $
45 .Fn zbootinit "vm_zone_t z" "char *name" "int size" "void *item" "int nitems"
47 .Fn zinitna "vm_zone_t z" "struct vm_object *obj" "char *name" "int size" "int nentries" "int flags" "int zalloc"
49 .Fn zinit "char *name" "int size" "int nentries" "int flags" "int zalloc"
51 .Fn zdestroy "vm_zone_t z"
53 .Fn zalloc "vm_zone_t z"
55 .Fn zfree "vm_zone_t z" "void *item"
57 The zone allocator is deprecated.
62 The zone allocator provides an efficient interface for managing
63 dynamically-sized collections of items of similar size.
64 The zone allocator can work with preallocated zones as well as with
65 runtime-allocated ones, and is therefore available much earlier in the
66 boot process than other memory management routines.
68 A zone is an extensible collection of items of identical size.
69 The zone allocator keeps track of which items are in use and which
70 are not, and provides functions for allocating items from the zone and
71 for releasing them back (which makes them available for later use).
73 The zone allocator stores state information inside the items proper
74 while they are not allocated,
75 so structures that will be managed by the zone allocator
76 and wish to use the type stable property of zones by leaving some fields
77 pre-filled between allocations, must reserve
78 two pointers at the very beginning for internal use by the zone
79 allocator, as follows:
82 struct my_item *z_rsvd1;
83 struct my_item *z_rsvd2;
84 /* rest of structure */
88 Alternatively they should assume those entries corrupted
89 after each allocation.
90 After the first allocation of an item,
91 it will have been cleared to zeroes, however subsequent allocations
92 will retain the contents as of the last free, with the exception of the
93 fields mentioned above.
95 Zones are created in one of two fashions, depending how far along the
98 If the VM system is fully initialized, a dynamically allocated zone can
103 argument should be a pointer to a short, descriptive name for the
104 zone; it is used for statistics and debugging purposes.
109 are the size of the items held by the zone and the initial size (in
110 items) of the zone, respectively.
113 argument should have the
115 bit set if there is a chance that items may be allocated from the zone in
116 interrupt context; note that in this case, the zone will never grow
122 argument should have the
124 bit set if the zone is to be destroyed with
128 indicates the number of VM pages by which the zone should grow every
131 If the VM system is not yet fully initialized, the zone allocator
132 cannot dynamically allocate VM pages from which to dole out items, so
133 the caller needs to provide a static pool of items.
134 In this case, the initialization is done in two stages: first,
136 is called before first use of the zone; later, when the VM system is
137 up, the initialization of the zone is completed by calling
140 The first argument to
142 is a pointer to a static
145 The second and third are the name of the zone and the size of the
147 The fourth argument is a pointer to a static array of items from which
148 the zone allocator will draw until the zone is fully initialized.
151 argument is the number of items in the array.
157 with the addition of a pointer to the zone to initialize, and a
159 .Vt "struct vm_object"
160 from which to allocate pages in the
164 To release all the memory allocated for a zone, call
166 Only zones created with
170 flag can be destroyed.
172 To allocate an item from a zone, simply call
174 with a pointer to that zone; it will return a pointer to an item, or
176 in the rare case where all items in the zone are in use and the
177 allocator is unable to grow the zone.
179 Items are released back to the zone from which they were allocated by
182 with a pointer to the zone and a pointer to the item.
184 The zone functions are not SMP-safe.
185 The MP lock must be held while calling them.
189 function returns 1 on success and 0 on failure; the only failure case
190 is inability to preallocate address space for an interrupt-safe zone.
194 function returns a pointer to a fully initialized
195 .Vt "struct vm_zone" ,
204 flag was specified and
206 failed to preallocate address space.
210 function returns a pointer to an item, or
212 if the zone ran out of unused items and the allocator was unable to
217 The zone allocator first appeared in
221 The zone allocator was written by
224 This manual page was written by
225 .An Dag-Erling Co\(:idan Sm\(/orgrav Aq des@FreeBSD.org .