2001-07-18 06:09:13 +00:00
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.\"
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.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice(s), this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified other than the possible
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.\" addition of one or more copyright notices.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice(s), this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
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.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
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.\" DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 13, 2001
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.Dt VM_PAGE_HOLD 9
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.Os
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.Sh NAME
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.Nm vm_page_hold ,
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.Nm vm_page_unhold
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2001-08-08 10:04:08 +00:00
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.Nd "update a page's hold count"
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2001-07-18 06:09:13 +00:00
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.Sh SYNOPSIS
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.In sys/param.h
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.In vm/vm.h
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.In vm/vm_page.h
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.Ft void
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.Fn vm_page_hold "vm_page_t m"
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.Ft void
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.Fn vm_page_unhold "vm_page_t m"
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.Sh DESCRIPTION
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The
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.Fn vm_page_hold
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function increases the hold count on a page.
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This prevents the page daemon from freeing the page.
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2001-07-30 22:14:23 +00:00
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.Pp
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.Fn vm_page_hold
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should only be used for very temporary wiring of a page,
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as that page will not be considered for paging or
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reallocation for as long as its hold count is greater
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than zero.
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Also note that while wired pages are removed from whatever
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queue they are on,
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2001-07-18 06:09:13 +00:00
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.Fn vm_page_hold
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2001-07-30 22:14:23 +00:00
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does not affect the location of the page.
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If it is on a queue prior to the call, it will still
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be there afterward.
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.Pp
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If the page needs to be held for a long period of time,
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2002-04-05 08:05:11 +00:00
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.Xr vm_page_wire 9
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2001-07-18 06:09:13 +00:00
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should be used.
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.Pp
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.Fn vm_page_unhold
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function reduces the hold count on a page.
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2001-08-08 10:04:08 +00:00
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If the hold count is zero it is possible that the page will be freed by the
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2001-07-18 06:09:13 +00:00
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page daemon.
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.Sh SEE ALSO
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2001-08-08 10:04:08 +00:00
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.Xr vm_page_unwire 9 ,
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2001-07-18 06:09:13 +00:00
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.Xr vm_page_wire 9
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.Sh AUTHORS
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2001-07-30 22:14:23 +00:00
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This manual page was written by
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2001-07-18 06:09:13 +00:00
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.An Chad David Aq davidc@acns.ab.ca .
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