2 .\" Copyright (c) 2001 Dag-Erling Coïdan Smørgrav
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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 1.4 2006/10/19 20:44:00 swildner 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 zalloc "vm_zone_t z"
52 .Fn zfree "vm_zone_t z" "void *item"
54 The zone allocator provides an efficient interface for managing
55 dynamically-sized collections of items of similar size.
56 The zone allocator can work with preallocated zones as well as with
57 runtime-allocated ones, and is therefore available much earlier in the
58 boot process than other memory management routines.
60 A zone is an extensible collection of items of identical size.
61 The zone allocator keeps track of which items are in use and which
62 are not, and provides functions for allocating items from the zone and
63 for releasing them back (which makes them available for later use).
65 The zone allocator stores state information inside the items proper
66 while they are not allocated,
67 so structures that will be managed by the zone allocator
68 and wish to use the type stable property of zones by leaving some fields
69 pre-filled between allocations, must reserve
70 two pointers at the very beginning for internal use by the zone
71 allocator, as follows:
74 struct my_item *z_rsvd1;
75 struct my_item *z_rsvd2;
76 /* rest of structure */
80 Alternatively they should assume those entries corrupted
81 after each allocation.
82 After the first allocation of an item,
83 it will have been cleared to zeroes, however subsequent allocations
84 will retain the contents as of the last free, with the exception of the
85 fields mentioned above.
87 Zones are created in one of two fashions, depending how far along the
90 If the VM system is fully initialized, a dynamically allocated zone can
95 argument should be a pointer to a short, descriptive name for the
96 zone; it is used for statistics and debugging purposes.
101 are the size of the items held by the zone and the initial size (in
102 items) of the zone, respectively.
105 argument should be set to
107 if there is a chance that items may be allocated from the zone in
108 interrupt context; note that in this case, the zone will never grow
117 indicates the number of VM pages by which the zone should grow every
120 If the VM system is not yet fully initialized, the zone allocator
121 cannot dynamically allocate VM pages from which to dole out items, so
122 the caller needs to provide a static pool of items.
123 In this case, the initialization is done in two stages: first,
125 is called before first use of the zone; later, when the VM system is
126 up, the initialization of the zone is completed by calling
129 The first argument to
131 is a pointer to a static
134 The second and third are the name of the zone and the size of the
136 The fourth argument is a pointer to a static array of items from which
137 the zone allocator will draw until the zone is fully initialized.
140 argument is the number of items in the array.
146 with the addition of a pointer to the zone to initialize, and a
148 .Vt "struct vm_object"
149 from which to allocate pages in the
153 To allocate an item from a zone, simply call
155 with a pointer to that zone; it will return a pointer to an item, or
157 in the rare case where all items in the zone are in use and the
158 allocator is unable to grow the zone.
163 functions are interrupt and SMP safe.
165 Items are released back to the zone from which they were allocated by
168 with a pointer to the zone and a pointer to the item.
172 function returns 1 on success and 0 on failure; the only failure case
173 is inability to preallocate address space for an interrupt-safe zone.
177 function returns a pointer to a fully initialized
178 .Vt "struct vm_zone" ,
187 flag was specified and
189 failed to preallocate address space.
193 function returns a pointer to an item, or
195 if the zone ran out of unused items and the allocator was unable to
200 The zone allocator first appeared in
204 The zone allocator was written by
207 This manual page was written by
208 .An Dag-Erling Co\(:idan Sm\(/orgrav Aq des@FreeBSD.org .