linux-kernel - Re: [test] sched: SD-latest versus Mike's latest

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Message-ID: <20070405190522.GA22092@elte.hu>
Date:	Thu, 5 Apr 2007 21:05:22 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Con Kolivas <kernel@...ivas.org>
Cc:	Mike Galbraith <efault@....de>,
	linux list <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	ck list <ck@....kolivas.org>
Subject: Re: [test] sched: SD-latest versus Mike's latest


* Con Kolivas <kernel@...ivas.org> wrote:

> Nice -10 on mainline ruins the latency of nice 0 tasks unlike SD. New 
> scheduling class just for X? Sounds like a very complicated 
> userspace-changing way to just do the equivalent of "nice -n -10" 
> obfuscated.

i think you are missing the point. We _do not know in advance_ whether X 
should be prioritized or not. It's the behavior of X that determines it. 
When X is reniced to -10 it fixes a few corner cases, but it breaks many 
other cases. We found that out time and time again.

btw., the tests i've done were not with X but using a shell prompt.

> > re-testing the weak points of SD:
> >
> >  - hackbench: still unusable under such type of high load - no 
> >  improvement.
> 
> Load of 160. Is proportional slowdown bad?

this is relative to how mainline+Mike's handles it. Users wont really 
care about the why's, they'll only see the slowdown.

> >  - make -j: still less interactive than Mike's - no improvement.
> 
> Depends on how big your job number vs cpu is. The better the 
> throttling gets with mainline the better SD gets in this comparison. 
> At equal fairness mainline does not have the low latency interactivity 
> SD has.

i often run make jobs with -j200 or larger, and SD gets worse than even 
mainline much sooner than that.

	Ingo
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