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I Have a Schedule to Keep - IO Schedulers

Oct 07, 2009, 15:32 (1 Talkback[s])
(Other stories by Jeffrey B. Layton)


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"The schedulers do exactly what the title says — they schedules activities within the kernel. Since this column is all about IO, the scheduler of interest is, aptly enough, the IO scheduler. This article discusses the IO scheduler concepts and the various options that are available.

"Introduction - IO Scheduler Concepts

"Virtually all applications running on Linux do some sort of IO. Even surfing the web produces a great number of small files that are written to disk. Without an IO scheduler, every time there is an IO request, there is an interrupt to the kernel and the IO operation is performed. More over, you can get a great mix of IO operations that move the disk head around the disk to satisfy read and write operations to different blocks on the drives. Perhaps more importantly, over time the disparity in the performance of disk drives and the rest of the system has grown very rapidly meaning that IO has become more important to overall system performance. As you can imagine when the kernel has to address the interrupt so any kind of processing or interactive work is paused. Consequently the system may appear unresponsive, or it may appear that the system has slowed down."

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