Kernel Korner - I/O Schedulers

Here's how I/O schedulers contribute to disk performance in Linux and the improvements you can get from the new I/O schedulers in the 2.6 kernel.
Acknowledgement

Andrea Arcangeli and Jens Axboe are the primary authors of the Linus Elevator. Jens Axboe is the primary author of the Deadline I/O Scheduler. Nick Piggin is the primary author of the Anticipatory I/O Scheduler.

Robert Love (rml@tech9.net) is a kernel hacker at MontaVista Software and a student at the University of Florida. He is the author of Linux Kernel Development. Robert loves O.A.R. and lives in Gainesville, Florida.

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Very informative read.

Binary Soldier's picture

Thanks for taking the time to publish this article.

I'm currently studying operating system fundamentals at university and it was great to read on it's usage in the Linux operating system. I had learned how Linux treats all hardware items as 'files', but reading this has given me a much more in-depth understanding.

*Bookmarked*

great article

procfs's picture

Hi this is grate, is there any other documents like this plain and symple

Thanks

Best regards

Nice article

Michael R. Hines's picture

I like this. It describes the problem to the point and nothing else. Thanks for writing it.

Re: Kernel Korner: I/O Schedulers

Anonymous's picture

Elementary my dear Watson.

That's only a mere 122 fold increase in test two.

Now for your next trick.......

Mick.

What about driver improvements?

Tom Callahan's picture

Your discounting the fact that there are many other performance enhancing improvements to the 2.6 kernel that have highly boosted read/write performance. Especially in the form of better supported IDE/SCSI devices and better drivers and feature sets.

I agree that anticipatory scheduler is MUCH better than the older schedulers, but recognize hardware/software improvements as well.

Anticipatory is not the best for everyone also, I recommend any person or company to run many many tests that will emulate your environment to test which scheduler is best for you...

-Tom

Nice article. However, I

Anonymous's picture

Nice article. However, I agree that schedulers needs to be tested in a particular environment to be sure which choice is best.

For example, AS is a poor choice for RAID and/or virtual machines. Virtual hosts with RAID disks appear to work best with the deadline elevator. VM guests should use the noop elevator so not to disguise physical access with virtual characteristics, let alone the ineffective and unnecessary overhead of using AS in a VM guest.

-shubes

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