| .\" -*- nroff -*- |
| .TH ELVTUNE 8 "14 March 2000" "Version 1.0" |
| .SH NAME |
| elvtune \- I/O elevator tuner |
| .SH SYNOPSIS |
| .B elvtune |
| .RB [ \-r |
| .IR r_lat ] |
| .RB [ \-w |
| .IR w_lat ] |
| .RB [ \-b |
| .IR b_max ] |
| .IR device ... |
| .br |
| .B elvtune \-h |
| .br |
| .B elvtune \-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/. |
