NDLI: Throttling On-Disk Schedulers to Meet Soft-Real-Time Requirements

Content Provider	IEEE Xplore Digital Library
Author	Stanovich, M.J. Baker, T.P. Wang, A.-I.A.
Copyright Year	2008
Description	Author affiliation: Dept. of Comput. Sci., Florida State Univ., Tallahassee, FL (Stanovich, M.J.; Baker, T.P.; Wang, A.-I.A.)
Abstract	Many contemporary disk drives have built-in queues and schedulers. These features can improve I/O performance, by offloading work from the system's main processor, avoiding disk idle time, and taking advantage of vendor-specific disk characteristics. At the same time, they pose challenges for scheduling requests that have real-time requirements, since the operating system has less visibility and control over service times. While it may be possible for an operating system to obtain more predictable real-time performance by bypassing the on-disk queue and scheduler, the diversity and continuing evolution of disk drives make it difficult to extract the necessary detailed timing characteristics of a specific disk, and to generalize that approach to all hard drives. This paper demonstrates three techniques we developed in the Linux operating system to bound real-time request response times for disks with internal queues and schedulers. The first technique is to use the disk's built-in starvation prevention scheme. The second is to prevent requests from being sent to the disk when real-time requests are waiting to be served. The third is to limit the length of the on-disk queue in addition to the second technique. Our results show the ability to guarantee a wide range of desired response times while still allowing the disk to perform scheduling optimizations. These techniques can be generalized to disks from different vendors.
Starting Page	331
Ending Page	341
File Size	538889
Page Count	11
File Format	PDF
ISBN	9780769531465
ISSN	15453421
DOI	10.1109/RTAS.2008.30
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2008-04-22
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Real time systems Job shop scheduling Real-time Deadline Application software Device driver Delay Computer science Disk drives Processor scheduling Operating systems Hard disk drive Hardware Timing Operating system
Content Type	Text
Resource Type	Article

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