3fbc2e00d1
from the local mapping. Enable the setting by default. The article behind the change: https://arxiv.org/abs/1901.01161 Reviewed by: markj Discussed with: emaste Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D18764
131 lines
3.9 KiB
Groff
131 lines
3.9 KiB
Groff
.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. 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, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, 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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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER 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
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)mincore.2 8.1 (Berkeley) 6/9/93
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.\" $FreeBSD$
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.\"
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.Dd January 7, 2019
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.Dt MINCORE 2
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.Os
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.Sh NAME
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.Nm mincore
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.Nd determine residency of memory pages
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/mman.h
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.Ft int
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.Fn mincore "const void *addr" "size_t len" "char *vec"
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.Sh DESCRIPTION
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The
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.Fn mincore
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system call determines whether each of the pages in the region beginning at
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.Fa addr
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and continuing for
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.Fa len
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bytes is resident or mapped, depending on the value of sysctl
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.Va vm.mincore_mapped .
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.\"The beginning address,
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.\".Fa addr ,
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.\"is first rounded down to a multiple of the page size (see
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.\".Xr getpagesize 3 ) .
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.\"The end address,
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.\".Fa addr No + Fa len ,
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.\"is rounded up to a multiple of the page size.
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The status is returned in the
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.Fa vec
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array, one character per page.
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Each character is either 0 if the page is not resident, or a combination of
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the following flags (defined in
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.In sys/mman.h ) :
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.Bl -tag -width ".Dv MINCORE_REFERENCED_OTHER"
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.It Dv MINCORE_INCORE
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Page is in core (resident).
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.It Dv MINCORE_REFERENCED
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Page has been referenced by us.
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.It Dv MINCORE_MODIFIED
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Page has been modified by us.
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.It Dv MINCORE_REFERENCED_OTHER
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Page has been referenced.
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.It Dv MINCORE_MODIFIED_OTHER
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Page has been modified.
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.It Dv MINCORE_SUPER
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Page is part of a large
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.Pq Dq super
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page.
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.El
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.Pp
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The information returned by
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.Fn mincore
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may be out of date by the time the system call returns.
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The only way to ensure that a page is resident is to lock it into memory
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with the
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.Xr mlock 2
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system call.
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.Pp
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If the
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.Va vm.mincore_mapped
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sysctl is set to a non-zero value (default), only the current process'
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mappings of the pages in the specified virtual address range are examined.
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This does not preclude the system from returning
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.Dv MINCORE_REFERENCED_OTHER
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and
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.Dv MINCORE_MODIFIED_OTHER
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statuses.
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Otherwise, if the sysctl value is zero, all resident pages backing the
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specified address range are examined, regardless of the mapping state.
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.Sh RETURN VALUES
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.Rv -std mincore
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.Sh ERRORS
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The
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.Fn mincore
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system call will fail if:
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.Bl -tag -width Er
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.It Bq Er ENOMEM
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The virtual address range specified by the
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.Fa addr
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and
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.Fa len
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arguments is not fully mapped.
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.It Bq Er EFAULT
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The
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.Fa vec
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argument points to an illegal address.
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.El
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.Sh SEE ALSO
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.Xr madvise 2 ,
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.Xr mlock 2 ,
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.Xr mprotect 2 ,
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.Xr msync 2 ,
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.Xr munmap 2 ,
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.Xr getpagesize 3
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.Sh HISTORY
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The
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.Fn mincore
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system call first appeared in
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.Bx 4.4 .
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