ELVTUNE(8)							    ELVTUNE(8)



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 performance and interactiveness. In the  out
       put  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.

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 sched
       uler. Its 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 use
       less.

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  SuSE



Version 1.0			 14 March 2000			    ELVTUNE(8)