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1.where is block I/O layer in the system
2.简介
The generic block I/O layer is an abstraction for blcok devices in the system
Receives I/O requests in a queue, and is responsible for passing them along to block devices.
The I/O requests are scheduled to be submitted to the devices by an algorithm called an I/O scheduler.
3.目标
maximize block I/O performance
4.技巧
must minimize latency, maximize throughput, and avoid starvation
5.You can check/set IO scheduler for a particular device via:
#cat /sys/block/sda/queue/scheduler
noop deadline [cfq]
#echo "noop" > /sys/block/sda/queue/scheduler
[noop] deadline cfq
1) The deadline I/O scheduler
Goal:fix starvation issue
Each request gets an expiration time. Defaults:500ms for reads, 5s for writes.
Three Queues:
Sorted queue
Read FIFO
Write FIFO
2) The Complete Fair Queuing I/O scheduler
3) The noop I/O scheduler
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原文地址：http://www.cnblogs.com/jason0401/p/5589779.html
