disk-utils/elvtune.8


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.\" -*- nroff -*-
.TH ELVTUNE 8 "14 March 2000" "Version 1.0"
.SH NAME
elvtune \- I/O elevator tuner
.SH SYNOPSIS
.B elvtune
[
.B \-r
.I r_lat
]
[
.B \-w
.I w_lat
]
[
.B \-b
.I b_max
]
.B /dev/blkdev1
[
.B /dev/blkdev2 ...
]

.B elvtune
.B -h

.B elvtune
.B -v
.SH DESCRIPTION
.B elvtune
allows to tune the I/O elevator per blockdevice queue basis. The
tuning can be safely done at runtime. Tuning the elevator means
being able to change disk performance and interactiveness. In the
output of elvtune the address of the queue tuned will be shown
and it can be considered as a queue ID.
For example multiple partitions in the same harddisk will
share the same queue and so tuning one partition will be
like tuning the whole HD.
.SH OPTIONS
.TP
.BI -r \ r_lat
set the max latency that the I/O scheduler will provide on
each read.
.TP
.BI -w \ w_lat
set the max latency that the I/O scheduler will provide on
each write.
.TP
.BI -b \ b_max
max coalescing factor allowed on writes when there are reads
pending in the queue.
.TP
.BI -h
help.
.TP
.BI -v
version.
.SH NOTE
Actually the only fields tunable are those relative
to the IO scheduler. It's not possible to select
a one-way or two-way elevator yet.
.PP
For logical blockdevices like LVM the tuning has to
be done on the
.I physical
devices. Tuning the queue of the LVM logical device
is useless.
.SH RETURN VALUE
0 on success and 1 on failure.
.SH HISTORY
Ioctls for tuning elevator behaviour were added in Linux 2.3.99-pre1.
.SH AUTHORS
Andrea Arcangeli <andrea@suse.de> SuSE
.SH AVAILABILITY
The elvtune command is part of the util-linux-ng package and is available from
ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.