.\"- .\" Copyright (c) 2001 Dag-Erling Coïdan Smørgrav .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" $FreeBSD: src/share/man/man9/zone.9,v 1.9.2.4 2002/05/02 20:01:29 asmodai Exp $ .\" .Dd April 6, 2018 .Dt ZONE 9 .Os .Sh NAME .Nm zbootinit , .Nm zinitna , .Nm zinit , .Nm zdestroy , .Nm zalloc , .Nm zfree .Nd zone allocator .Sh SYNOPSIS .In sys/param.h .In sys/queue.h .In vm/vm_zone.h .Ft void .Fn zbootinit "vm_zone_t z" "char *name" "size_t size" "void *item" "long nitems" .Ft int .Fn zinitna "vm_zone_t z" "char *name" "size_t size" "long nentries" "uint32_t flags" .Ft vm_zone_t .Fn zinit "char *name" "size_t size" "long nentries" "uint32_t flags" .Ft void .Fn zdestroy "vm_zone_t z" .Ft void * .Fn zalloc "vm_zone_t z" .Ft void .Fn zfree "vm_zone_t z" "void *item" .Sh DESCRIPTION The zone allocator is deprecated. Use .In sys/objcache.h for new developments. .Pp The zone allocator provides an efficient interface for managing dynamically-sized collections of items of similar size. The zone allocator can work with preallocated zones as well as with runtime-allocated ones, and is therefore available much earlier in the boot process than other memory management routines. .Pp A zone is an extensible collection of items of identical size. The zone allocator keeps track of which items are in use and which are not, and provides functions for allocating items from the zone and for releasing them back (which makes them available for later use). .Pp The zone allocator stores state information inside the items proper while they are not allocated, so structures that will be managed by the zone allocator and wish to use the type stable property of zones by leaving some fields pre-filled between allocations, must reserve two pointers at the very beginning for internal use by the zone allocator, as follows: .Bd -literal struct my_item { struct my_item *z_rsvd1; struct my_item *z_rsvd2; /* rest of structure */ }; .Ed .Pp Alternatively they should assume those entries corrupted after each allocation. After the first allocation of an item, it will have been cleared to zeroes, however subsequent allocations will retain the contents as of the last free, with the exception of the fields mentioned above. .Pp Zones are created in one of two fashions, depending how far along the boot process is. .Pp If the VM system is fully initialized, a dynamically allocated zone can be created using .Fn zinit . The .Fa name argument should be a pointer to a short, descriptive name for the zone; it is used for statistics and debugging purposes. The .Fa size and .Fa nentries are the size of the items held by the zone and the initial size (in items) of the zone, respectively. The .Fa flags argument should have the .Dv ZONE_INTERRUPT bit set if there is a chance that items may be allocated from the zone in interrupt context; note that in this case, the zone will never grow larger than .Fa nentries items. The .Fa flags argument should have the .Dv ZONE_DESTROYABLE bit set if the zone is to be destroyed with .Fn zdestroy . .Pp If the VM system is not yet fully initialized, the zone allocator cannot dynamically allocate VM pages from which to dole out items, so the caller needs to provide a static pool of items. In this case, the initialization is done in two stages: first, .Fn zbootinit is called before first use of the zone; later, when the VM system is up, the initialization of the zone is completed by calling .Fn zinitna . .Pp The first argument to .Fn zbootinit is a pointer to a static .Vt "struct vm_zone" to initialize. The second and third are the name of the zone and the size of the items it will hold. The fourth argument is a pointer to a static array of items from which the zone allocator will draw until the zone is fully initialized. The .Fa nitems argument is the number of items in the array. .Pp The arguments to .Fn zinitna are the same as for .Fn zinit , with the addition of a pointer to the zone to initialize. .Pp To release all the memory allocated for a zone, call .Fn zdestroy . Only zones created with .Fn zinit and with the .Dv ZONE_DESTROYABLE flag can be destroyed. .Pp To allocate an item from a zone, simply call .Fn zalloc with a pointer to that zone; it will return a pointer to an item, or .Dv NULL in the rare case where all items in the zone are in use and the allocator is unable to grow the zone. .Pp Items are released back to the zone from which they were allocated by calling .Fn zfree with a pointer to the zone and a pointer to the item. .Sh RETURN VALUES The .Fn zinitna function returns 1 on success and 0 on failure; the only failure case is inability to preallocate address space for an interrupt-safe zone. .Pp The .Fn zinit function returns a pointer to a fully initialized .Vt "struct vm_zone" , or .Dv NULL if it was unable to .Fn kmalloc a .Vt "struct vm_zone" or the .Dv ZONE_INTERRUPT flag was specified and .Fn zinitna failed to preallocate address space. .Pp The .Fn zalloc function returns a pointer to an item, or .Dv NULL if the zone ran out of unused items and the allocator was unable to enlarge it. .Sh SEE ALSO .Xr memory 9 .Sh HISTORY The zone allocator first appeared in .Fx 3.0 . .Sh AUTHORS .An -nosplit The zone allocator was written by .An John S. Dyson . .Pp This manual page was written by .An Dag-Erling Co\(:idan Sm\(/orgrav Aq Mt des@FreeBSD.org .