linux-kernel - Re: [ANNOUNCE/RFC] Really Fair Scheduler

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Message-ID: <alpine.LFD.0.999.0709021349290.22654@enigma.security.iitk.ac.in>
Date:	Sun, 2 Sep 2007 14:10:37 +0530 (IST)
From:	Satyam Sharma <satyam@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Daniel Walker <dwalker@...sta.com>,
	Roman Zippel <zippel@...ux-m68k.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	peterz@...radead.org
Subject: Re: [ANNOUNCE/RFC] Really Fair Scheduler

On Sun, 2 Sep 2007, Ingo Molnar wrote:
> 
> Although it _should_ have been a net code size win, because if you look 
> at the diff you'll see that other useful things were removed as well: 
> sleeper fairness, CPU time distribution smarts, tunings, scheduler 
> instrumentation code, etc.

To be fair to Roman, he probably started development off an earlier CFS,
most probably 2.6.23-rc3-git1, if I guess correctly from his original
posting. So it's likely he missed out on some of the tunings/comments(?)
etc code that got merged after that.

> > I also ran hackbench (in a haphazard way) a few times on it vs. CFS in 
> > my tree, and RFS was faster to some degree (it varied)..
> 
> here are some actual numbers for "hackbench 50" on -rc5, 10 consecutive 
> runs fresh after bootup, Core2Duo, UP:

Again, it would be interesting to benchmark against 2.6.23-rc3-git1. And
also probably rediff vs 2.6.23-rc3-git1 and compare how the code actually
changed ... but admittedly, doing so would be utterly pointless, because
much water has flowed down the Ganges since -rc3 (misc CFS improvements,
Peter's patches that you mentioned). So a "look, I told you so" kind of
situation wouldn't really be constructive at all.

> It would be far more reviewable and objectively judgeable on an item by 
> item basis if Roman posted the finegrained patches i asked for. (which 
> patch series should be sorted in order of intrusiveness - i.e. leaving 
> the harder changes to the end of the series.)

Absolutely. And if there indeed are net improvements (be it for corner
cases) over latest CFS-rc5, while maintaining performance for the common
cases at the same time, well, that can only be a good thing.

Just my Rs. 0.02,

Satyam
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