mirror of https://gitee.com/openkylin/samba.git
122 lines
3.3 KiB
Groff
122 lines
3.3 KiB
Groff
'\" t
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.\" Title: vfs_readahead
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.\" Author: [see the "AUTHOR" section]
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.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
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.\" Date: 01/28/2020
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.\" Manual: System Administration tools
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.\" Source: Samba 4.11.6
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.\" Language: English
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.\"
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.TH "VFS_READAHEAD" "8" "01/28/2020" "Samba 4\&.11\&.6" "System Administration tools"
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.\" -----------------------------------------------------------------
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.\" * Define some portability stuff
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.\" -----------------------------------------------------------------
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.\" http://bugs.debian.org/507673
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.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.ie \n(.g .ds Aq \(aq
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.el .ds Aq '
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.\" -----------------------------------------------------------------
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.\" * set default formatting
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.\" -----------------------------------------------------------------
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.\" disable hyphenation
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.nh
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.\" disable justification (adjust text to left margin only)
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.ad l
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.\" -----------------------------------------------------------------
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.\" * MAIN CONTENT STARTS HERE *
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.\" -----------------------------------------------------------------
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.SH "NAME"
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vfs_readahead \- pre\-load the kernel buffer cache
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.SH "SYNOPSIS"
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.HP \w'\ 'u
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vfs objects = readahead
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.SH "DESCRIPTION"
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.PP
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This VFS module is part of the
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\fBsamba\fR(7)
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suite\&.
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.PP
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This
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vfs_readahead
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VFS module detects read requests at multiples of a given offset (hex 0x80000 by default) and then tells the kernel via either the readahead system call (on Linux) or the posix_fadvise system call to pre\-fetch this data into the buffer cache\&.
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.PP
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This module is useful for Windows Vista clients reading data using the Windows Explorer program, which asynchronously does multiple file read requests at offset boundaries of 0x80000 bytes\&.
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.PP
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The offset multiple used is given by the readahead:offset option, which defaults to 0x80000\&.
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.PP
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The size of the disk read operations performed by
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vfs_readahead
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is determined by the readahead:length option\&. By default this is set to the same value as the readahead:offset option and if not set explicitly will use the current value of readahead:offset\&.
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.PP
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This module is stackable\&.
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.SH "OPTIONS"
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.PP
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readahead:offset = BYTES
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.RS 4
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The offset multiple that causes readahead to be requested of the kernel buffer cache\&.
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.RE
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.PP
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readahead:length = BYTES
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.RS 4
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The number of bytes requested to be read into the kernel buffer cache on each readahead call\&.
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.RE
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.PP
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The following suffixes may be applied to BYTES:
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.RS
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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K
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\- BYTES is a number of kilobytes
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.RE
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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M
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\- BYTES is a number of megabytes
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.RE
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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G
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\- BYTES is a number of gigabytes
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.RE
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.SH "EXAMPLES"
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.sp
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.if n \{\
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.RS 4
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.\}
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.nf
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\fI[hypothetical]\fR
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\m[blue]\fBvfs objects = readahead\fR\m[]
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.fi
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.if n \{\
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.RE
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.\}
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.SH "VERSION"
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.PP
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This man page is part of version 4\&.11\&.6 of the Samba suite\&.
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.SH "AUTHOR"
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.PP
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The original Samba software and related utilities were created by Andrew Tridgell\&. Samba is now developed by the Samba Team as an Open Source project similar to the way the Linux kernel is developed\&.
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