An Evaluation of Linux I/O Scheduler Behavior at the Block I/O Layer

Linux IO Scheduler

Sinha, Subhas Kumar ; Dr. Khaled Harfoush, Committee Member,Dr. Xiaohui Gu, Committee Member,Dr. Vincent Freeh, Committee Chair,Sinha, Subhas Kumar ; Dr. Khaled Harfoush ; Committee Member ; Dr. Xiaohui Gu ; Committee Member ; Dr. Vincent Freeh ; Committee Chair

University:North Carolina State University

关键词: Linux IO Scheduler;   

Others  :  https://repository.lib.ncsu.edu/bitstream/handle/1840.16/632/etd.pdf?sequence=1&isAllowed=y

美国|英语

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【 摘 要 】

Linux comes with four different I⁄O schedulers - NOOP, Deadline, Anticipatory, and Complete Fairness Queuing (CFQ). Each scheduler attempts to reduce overall response time using different algorithms involving ordering and merging of I⁄O requests. These schedulers tend to behave differently for different types of workloads.In this study we validate the behavior of the different I⁄O schedulers at the block I⁄O layer, present our observations and and give our recomomendation regarding what could be the right scheduler for a particular environment. We have restricted our study to a desktop environment.To capture block I⁄O layer events we use a combination of blktrace (a block I⁄O layer trace tool) and systemtap (a running kernel trace tool). We have captured I⁄O traces forthe different schedulers under different application loads. Hard disk queuing effects of SATA⁄ SCSI have an impact on I⁄O behavior and we evaluate this behavior by running our tests on different types of disks. All our tests were run on the ext3 filesystem.