linux-kernel - Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS]

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Date:	Sat, 14 Apr 2007 01:44:44 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	William Lee Irwin III <wli@...omorphy.com>
Cc:	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Con Kolivas <kernel@...ivas.org>,
	Nick Piggin <npiggin@...e.de>, Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS]


* William Lee Irwin III <wli@...omorphy.com> wrote:

> Where it gets complex is when the behavior patterns vary, e.g. they're 
> not entirely CPU-bound and their desired in-isolation CPU utilization 
> varies, or when nice levels vary, or both vary. [...]

yes. I tested things like 'massive_intr.c' (attached, written by Satoru 
Takeuchi) which starts N tasks which each work for 8msec then sleep 
1msec:

from its output, the second column is the CPU time each thread got, the 
more even, the fairer the scheduling. On vanilla i get:

 mercury:~> ./massive_intr 10 10
 024873  00000150
 024874  00000123
 024870  00000069
 024868  00000068
 024866  00000051
 024875  00000206
 024872  00000093
 024869  00000138
 024867  00000078
 024871  00000223

on CFS i get:

 neptune:~> ./massive_intr 10 10
 002266  00000112
 002260  00000113
 002261  00000112
 002267  00000112
 002269  00000112
 002265  00000112
 002262  00000113
 002268  00000113
 002264  00000112
 002263  00000113

so it is quite a bit more even ;)

another related test-utility is one i wrote:

  http://people.redhat.com/mingo/scheduler-patches/ring-test.c

this is a ring of 100 tasks each doing work for 100 msecs and then 
sleeping for 1 msec. I usually test this by also running a CPU hog in 
parallel to it, and checking whether it gets ~50.0% of CPU time under 
CFS. (it does)

	Ingo

View attachment "massive_intr.c" of type "text/plain" (9834 bytes)