Browse Prior Art Database

Efficient Disk Activity Light

IP.com Disclosure Number: IPCOM000117773D
Original Publication Date: 1996-Jun-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Bruce, MG: AUTHOR

Abstract

Disclosed is a method to reduce the operating system pathlength required to manage a disk activity light. The disk activity light is updated with a background timer, instead of on every disk operation.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Efficient Disk Activity Light

      Disclosed is a method to reduce the operating system pathlength
required to manage a disk activity light.  The disk activity light is
updated with a background timer, instead of on every disk operation.

      To reduce the path length required to write the disklight, its
state is changed in the operating systems timer interrupt routine.
Most operating systems have a timer that runs 100s of times a second.

      Rather then update the disk light on each idle/busy transition,
a state is maintained in a global variable.  This can be done
efficiently using an atomic add or subtract.  The global variable is
checked in the  systems timer interrupt service routine, and the disk
activity is updated  if its current value is not correct.

      This is more efficient for two reasons.  First the number of
disklight writes does not increase with the number of IOs.  Its
maximum update rate is the system timer period.  Second, for SMP
systems the serialization required to update a global variable is
simpler then what  is required to maintain the state of the
disklight.