linux-kernel - Re: [REPORT] cfs-v4 vs sd-0.44

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Date:	Sat, 21 Apr 2007 19:15:19 +0200 (MEST)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Con Kolivas <kernel@...ivas.org>, Willy Tarreau <w@....eu>,
	William Lee Irwin III <wli@...omorphy.com>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>, Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Peter Williams <pwil3058@...pond.net.au>,
	Thomas Gleixner <tglx@...utronix.de>, caglar@...dus.org.tr,
	Gene Heskett <gene.heskett@...il.com>
Subject: Re: [REPORT] cfs-v4 vs sd-0.44


On Apr 21 2007 18:00, Ingo Molnar wrote:
>* Con Kolivas <kernel@...ivas.org> wrote:
>
>> >   Feels even better, mouse movements are very smooth even under high 
>> >   load. I noticed that X gets reniced to -19 with this scheduler. 
>> >   I've not looked at the code yet but this looked suspicious to me. 
>> >   I've reniced it to 0 and it did not change any behaviour. Still 
>> >   very good.
>> 
>> Looks like this code does it:
>> 
>> +int sysctl_sched_privileged_nice_level __read_mostly = -19;
>
>correct. Note that Willy reniced X back to 0 so it had no relevance on 
>his test. Also note that i pointed this change out in the -v4 CFS 
>announcement:
>
>|| Changes since -v3:
>||
>||  - usability fix: automatic renicing of kernel threads such as 
>||    keventd, OOM tasks and tasks doing privileged hardware access
>||    (such as Xorg).
>
>i've attached it below in a standalone form, feel free to put it into 
>SD! :)

Assume X went crazy (lacking any statistics, I make the unproven
statement that this happens more often than kthreads going berserk),
then having it niced with minus something is not too nice.



Jan
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