freebsd-nq/share/man/man9/vm_map_wire.9

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.Dd July 19, 2003
.Dt VM_MAP_WIRE 9
.Os
.Sh NAME
.Nm vm_map_wire ,
.Nm vm_map_unwire
.Nd manage page wiring within a virtual memory map
.Sh SYNOPSIS
.In sys/param.h
.In vm/vm.h
.In vm/vm_map.h
.Ft int
.Fn vm_map_wire "vm_map_t map" "vm_offset_t start" "vm_offset_t end" "int flags"
.Ft int
.Fo vm_map_unwire
.Fa "vm_map_t map" "vm_offset_t start" "vm_offset_t end" "int flags"
.Fc
.Sh DESCRIPTION
The
.Fn vm_map_wire
function is responsible for wiring pages in the range between
.Fa start
and
.Fa end
within the map
.Fa map .
Wired pages are locked into physical memory, and may not be paged out
as long as their wire count remains above zero.
.Pp
The
.Fn vm_map_unwire
function performs the corresponding unwire operation.
.Pp
The
.Fa flags
argument is a bit mask, consisting of the following flags:
.Pp
If the
.Dv VM_MAP_WIRE_USER
flag is set, the function operates within user address space.
.Pp
If the
.Dv VM_MAP_WIRE_HOLESOK
flag is set, it may operate upon an arbitrary range within the
address space of
.Fa map .
.Pp
If a contiguous range is desired, callers should explicitly express
their intent by specifying the
.Dv VM_MAP_WIRE_NOHOLES
flag.
.Sh IMPLEMENTATION NOTES
Both functions will attempt to acquire a lock on the map using
.Xr vm_map_lock 9
and hold it for the duration of the call.
If they detect
.Dv MAP_ENTRY_IN_TRANSITION ,
they will call
.Xr vm_map_unlock_and_wait 9
until the map becomes available again.
.Pp
The map could have changed during this window as it was held by another
consumer, therefore consumers of this interface should check for this
condition using the return values below.
.Sh RETURN VALUES
The
.Fn vm_map_wire
and
.Fn vm_map_unwire
functions have identical return values.
The functions return
.Dv KERN_SUCCESS
if all pages within the range were [un]wired successfully.
.Pp
Otherwise, if the specified range was not valid,
or if the map changed while the
.Dv MAP_ENTRY_IN_TRANSITION
flag was set,
.Dv KERN_INVALID_ADDRESS
is returned.
.Sh SEE ALSO
.Xr mlockall 2 ,
.Xr munlockall 2 ,
.Xr vm_map 9
.Sh AUTHORS
This manual page was written by
.An Bruce M Simpson Aq bms@spc.org .