'\" t
.\"     Title: vfs_readahead
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
.\"      Date: 02/21/2015
.\"    Manual: System Administration tools
.\"    Source: Samba 4.0
.\"  Language: English
.\"
.TH "VFS_READAHEAD" "8" "02/21/2015" "Samba 4\&.0" "System Administration tools"
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.SH "NAME"
vfs_readahead \- pre\-load the kernel buffer cache
.SH "SYNOPSIS"
.HP \w'\ 'u
vfs objects = readahead
.SH "DESCRIPTION"
.PP
This VFS module is part of the
\fBsamba\fR(7)
suite\&.
.PP
This
vfs_readahead
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\&.
.PP
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\&.
.PP
The offset multiple used is given by the readahead:offset option, which defaults to 0x80000\&.
.PP
The size of the disk read operations performed by
vfs_readahead
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\&.
.PP
This module is stackable\&.
.SH "OPTIONS"
.PP
readahead:offset = BYTES
.RS 4
The offset multiple that causes readahead to be requested of the kernel buffer cache\&.
.RE
.PP
readahead:length = BYTES
.RS 4
The number of bytes requested to be read into the kernel buffer cache on each readahead call\&.
.RE
.PP
The following suffixes may be applied to BYTES:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
K
\- BYTES is a number of kilobytes
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
M
\- BYTES is a number of megabytes
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
G
\- BYTES is a number of gigabytes
.RE
.SH "EXAMPLES"
.sp
.if n \{\
.RS 4
.\}
.nf
	\fI[hypothetical]\fR
	\m[blue]\fBvfs objects = readahead\fR\m[]
.fi
.if n \{\
.RE
.\}
.SH "VERSION"
.PP
This man page is correct for version 3\&.0\&.25 of the Samba suite\&.
.SH "AUTHOR"
.PP
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\&.