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.IX Title "FS_PRECACHE 1"
.TH FS_PRECACHE 1 2024-03-20 OpenAFS "AFS Command Reference"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH NAME
fs_precache \- Set precache size
.SH SYNOPSIS
.IX Header "SYNOPSIS"
\&\fBfs precache\fR \fB\-blocks\fR\ <\fIsize\ in\ 1K\ blocks\fR>
    [\fB\-help\fR]
.PP
\&\fBfs p\fR \fB\-b\fR\ <\fIsize\ in\ 1K\ blocks\fR>
    [\fB\-h\fR]
.SH DESCRIPTION
.IX Header "DESCRIPTION"
The \fBfs precache\fR command configures to what degree the Cache Manager will
attempt to prefetch cache blocks when an application opens a file for reading.
If this behavior is enabled, whenever a file is opened for reading, the Cache
Manager will immediately initiate an asynchronous fetch request for that file.
This fetch request will fetch the configured amount of data for that file, and
store the data in the cache. In some scenarios, this can improve performance.
.PP
Note that this prefetching behavior is done by the Cache Manager itself. The
underlying Operating System may also perform its own prefetching behavior,
depending on various settings or application hints.
.PP
This command was introduced in OpenAFS 1.5.37.
.SH OPTIONS
.IX Header "OPTIONS"
.IP "\fB\-blocks\fR <\fIsize in 1K blocks\fR>" 4
.IX Item "-blocks <size in 1K blocks>"
Specifies how much data to prefetch for each applicable file, in 1024\-byte
blocks. Specify 0 to disable prefetching behavior. By default, prefetching is
disabled.
.IP \fB\-help\fR 4
.IX Item "-help"
Prints the online help for this command. All other valid options are
ignored.
.SH OUTPUT
.IX Header "OUTPUT"
If the specified precache size has been set successfully, the following message
will be printed:
.PP
.Vb 1
\&   New precache size set.
.Ve
.SH EXAMPLES
.IX Header "EXAMPLES"
The following command configures the Cache Manager to prefetch the first 100
kilobytes of any file that's opened for reading:
.PP
.Vb 2
\&   % fs precache \-blocks 100
\&   New precache size set.
.Ve
.SH "PRIVILEGE REQUIRED"
.IX Header "PRIVILEGE REQUIRED"
The issuer must be logged in as the local superuser \f(CW\*(C`root\*(C'\fR.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBafsd\fR\|(8)
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright 2013 Sine Nomine Associates
.PP
This documentation is covered by the BSD License as written in the
doc/LICENSE file. This man page was written by Andrew Deason for
OpenAFS.