elvtune



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. 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 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 <andrea@suse.de> SuSE



Version 1.0                      14 March 2000                      ELVTUNE(8)

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