关于CFS/BFS调度算法

(2010-10-27 17:36:56)

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http://www.cs.unm.edu/~eschulte/data/bfs-v-cfs_groves-knockel-schulte.pdf

BFS vs. CFS Scheduler Comparison

Taylor Groves, Jeff Knockel, Eric Schulte

11 December 2009

Abstract

In 2007 a dispute erupted on the Linux kernel mailing list. The

dispute was between Con

Kolivas, creater of the Staricase Deadline (SD) scheduler and Ingo

Molnar, whose newly released

Completely Fair Scheduler (CFS) was to be added to the mainline.

CFS employed concepts

previously envisioned by Kolivas and the dispute ended with Kolivas

leaving the mainline kernel

development community. Two years later Kolivas released the Brain

Fuck Scheduler (BFS) with

a focus on a simplistic design, tailored towards interactive

workloads on commodity personal

computers with a reasonable number of cores. We review the

mechanisms of the CFS and BFS

schedulers and test both on a variety of single-user hardware over

a variety of workloads with a

strong focus on the range of "normal" PC use. Our results indicate

that scheduler performance

varies dramatically according to hardware and workload, and as a

result we strongly encourage

Linux distributions to take an increased level of responsibility

for selecting appropriate default

schedulers that best suit the intended usage of the system.

Introduction

Given the wide range of hardware running the Linux kernel it is

dicult to provide a single CPU

scheduler that performs well in all platforms and use cases. Many

metrics of scheduler performance

such as latency and turnaround time can be at odds - improving one

metric will often reduce

performance on another. We investigate the performance of two CPU

schedulers the Completely

Fair Scheduler (CFS) and the Brain Fuck Scheduler (BFS) available

for the modern Linux

kernel. Our tests are primarily aimed at the personal computers

environment. We nd that often

the best scheduler depends on the system and expected use cases and

as a result we conclude that

it is appropriate to select a CPU scheduler with these factors in

mind.

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