ELVTUNE(E)                                             ELVTUNE(E)



NAME
       elvtune - I/O elevator tuner

SYNOPSIS
       elvtune  [  -r  r_lat  ]  [  -w  w_lat  ]  [  -b  b_max  ]
       /dev/blkdev1 [ /dev/blkdev2 ...  ]

       elvtune -h

       elvtune -v

DESCRIPTION
       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  per-
       formance 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 tun-
       ing one partition will be like tuning the whole HD.

OPTIONS
       -r r_lat
              set  the  max  latency  that the I/O scheduler will
              provide on each read.

       -w w_lat
              set the max latency that  the  I/O  scheduler  will
              provide on each write.

       -b b_max
              max  coalescing factor allowed on writes when there
              are reads pending in the queue.

       -h     help.

       -v     version.

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.

       For logical blockdevices like LVM the  tuning  has  to  be
       done  on the physical devices. Tuning the queue of the LVM
       logical device is useless.

RETURN VALUE
       0 on success and 1 on failure.

HISTORY
       Ioctls for tuning elevator behaviour were added  in  Linux
       2.3.99-pre1.

AUTHORS
       Andrea Arcangeli <andrea@suse.de> SuSE



Version 1.0               14 March 2000                ELVTUNE(E)