process - Linux 内核 : Targeted Latency vs Minimum Granularity

Question

在 Linux 内核的 CFS 调度程序的上下文中， 之间最重要的区别是什么？目标延迟 和 最小粒度 .

或者我们如何定义目标延迟 和 最小粒度 .

数学解释受到高度赞赏。

Answer 1

how do we define Targeted Latency and Minimum Granularity.

来自 Robert Love 的“Linux 内核开发”:

1)

CFS sets a target for its approximation of the “infinitely small” scheduling duration in perfect multitasking. This target is called the targeted latency.

2)

Note as the number of runnable tasks approaches infinity, the proportion of allotted processor and the assigned timeslice approaches zero. As this will eventually result in unacceptable switching costs, CFS imposes a floor on the timeslice assigned to each process.This floor is called the minimum granularity.

因此，目标延迟是所有运行队列任务至少被调度一次的时间段。最小粒度是任务在被抢占之前允许在 CPU 上运行的最短时间。

引用:

http://oakbytes.wordpress.com/2012/06/06/linux-scheduler-cfs-and-latency/

http://doc.opensuse.org/products/draft/SLES/SLES-tuning_sd_draft/cha.tuning.taskscheduler.html

http://www.google.ru/search?q=Robert+Love+Linux+Kernel+development&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:ru:official&client=firefox-a&channel=sb&gfe_rd=cr&ei=qZcQVIyeCMaA8Ab7wYGYBw