disk-utils/elvtune.8

   1 .\" -*- nroff -*-
   2 .TH ELVTUNE 8 "March 2000" "util-linux" "System Administration"
   3 .SH NAME
   4 elvtune \- I/O elevator tuner
   5 .SH SYNOPSIS
   6 .B elvtune
   7 .RB [ \-r
   8 .IR r_lat ]
   9 .RB [ \-w
  10 .IR w_lat ]
  11 .RB [ \-b
  12 .IR b_max ]
  13 .IR device ...
  14 .br
  15 .B elvtune \-h
  16 .br
  17 .B elvtune \-v
  18 .SH DESCRIPTION
  19 .B elvtune
  20 allows to tune the I/O elevator per blockdevice queue.  The
  21 tuning can be safely done at runtime.  Tuning the elevator means
  22 being able to change disk performance and interactiveness.
  23 In the output of
  24 .B elvtune
  25 the address of the queue tuned will be shown;
  26 it can be considered as a queue ID.
  27 Multiple partitions on the same harddisk will
  28 share the same queue and so tuning one partition will be
  29 like tuning the whole HD.
  30 .SH OPTIONS
  31 .TP
  32 .BI -r \ r_lat
  33 Set the maximum latency that the I/O scheduler will provide on
  34 each read.
  35 .TP
  36 .BI -w \ w_lat
  37 Set the maximum latency that the I/O scheduler will provide on
  38 each write.
  39 .TP
  40 .BI -b \ b_max
  41 Set the maximum coalescing factor allowed on writes when there are reads
  42 pending in the queue.
  43 .TP
  44 .BI -h
  45 Display help text and exit.
  46 .TP
  47 .BI -v
  48 Display version information and exit.
  49 .SH NOTE
  50 Actually, the only fields tunable are those relative
  51 to the IO scheduler.  It's not possible to select
  52 a one-way or two-way elevator yet.
  53 .PP
  54 For logical blockdevices like LVM the tuning has to
  55 be done on the
  56 .I physical
  57 devices.  Tuning the queue of the LVM logical device
  58 is useless.
  59 .SH RETURN VALUE
  60 0 on success and 1 on failure.
  61 .SH HISTORY
  62 Ioctls for tuning elevator behaviour were added in Linux 2.3.99-pre1.
  63 .SH AUTHORS
  64 Andrea Arcangeli <andrea@suse.de> SuSE
  65 .SH AVAILABILITY
  66 The elvtune command is part of the util-linux package and is available from
  67 ftp://ftp.kernel.org/pub/linux/utils/util-linux/.