Anticipatory scheduling: A disk scheduling framework to overcome deceptive idleness in synchronous I/O

Disk schedulers in current operating systems are generally work-conserving, i.e., they schedule a request as soon as the previous request has finished. Such schedulers often require multiple outstanding requests from each process to meet system-level goals of performance and quality of service. Unfortunately, many common applications issue disk read requests in a synchronous manner, interspersing successive requests with short periods of computation. The scheduler chooses the next request too early; this induces deceptive idleness, a condition where the scheduler incorrectly assumes that the last request issuing process has no further requests, and becomes forced to switch to a request from another process. We propose the anticipatory disk scheduling framework to solve this problem in a simple, general and transparent way, based on the non-work-conserving scheduling discipline. Our FreeBSD implementation is observed to yield large benefits on a range of microbenchmarks and real work...

• Type: Conference
• Year: 2001
• Where: SOSP
• Authors: Sitaram Iyer, Peter Druschel
• Keywords: Disk Read Requests, Disk Schedulers, Operating System, Request Issuing Process, SOSP 2001