101 lines
3.1 KiB
Groff
101 lines
3.1 KiB
Groff
.\"
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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 August 31, 2011
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.Dt VM_PAGE_AFLAG 9
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.Os
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.Sh NAME
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.Nm vm_page_aflag_clear , vm_page_aflag_set , vm_page_reference
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.Nd "change page atomic flags"
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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_aflag_clear "vm_page_t m" "uint8_t bits"
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.Ft void
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.Fn vm_page_aflag_set "vm_page_t m" "uint8_t bits"
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.Ft void
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.Fn vm_page_reference "vm_page_t m"
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.Sh DESCRIPTION
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The
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.Fn vm_page_aflag_clear
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atomically clears the specified bits on the page's
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.Va aflags .
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.Pp
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The
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.Fn vm_page_aflag_set
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atomically sets the specified bits on the page's
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.Va aflags .
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.Pp
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The
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.Fn vm_page_reference m
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call is the same as
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.Bd -literal -offset indent
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vm_page_aflag_set(m, PGA_REFERENCED);
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.Ed
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.Lp
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and is the recommended way to mark the page as referenced from
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third-party kernel modules.
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.Pp
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These functions neither block nor require any locks to be held
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around the calls for correctness.
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.Pp
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The functions arguments are:
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.Bl -tag -width ".Fa bits"
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.It Fa m
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The page whose
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.Va aflags
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are updated.
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.It Fa bits
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The bits that are set or cleared on the page's flags.
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.El
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.Pp
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The following
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.Va aflags
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can be set or cleared:
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.Bl -tag -width ".Fa PGA_REFERENCED"
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.It Fa PGA_REFERENCED
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The bit may be set to indicate that the page has been recently accessed.
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For instance,
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.Xr pmap 9
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sets this bit to reflect the accessed attribute of the page mapping
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typically updated by processor's memory management unit on the page access.
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.It Fa PGA_WRITEABLE
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A writeable mapping for the page may exist.
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.El
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.Pp
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Both
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.Dv PGA_REFERENCED
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and
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.Dv PGA_WRITEABLE
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bits are only valid for the managed pages.
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.Sh AUTHORS
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This manual page was written by
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.An Chad David Aq Mt davidc@acns.ab.ca .
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