linux-kernel - Re: (ondemand) CPU governor regression between 2.6.23 and 2.6.24

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Date:	Mon, 28 Jan 2008 16:16:02 +0100
From:	Toralf Förster <toralf.foerster@....de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Mike Galbraith <efault@....de>, Sam Ravnborg <sam@...nborg.org>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: (ondemand) CPU governor  regression between 2.6.23 and 2.6.24

Hello,

At Monday 28 January 2008 Ingo Molnar wrote :
> 
> it splits the CPU time between Xorg (root UID) and desktop apps. This 
> helps particularly well when there's compile jobs going on, etc. - Xorg 
good news for all Gentoo users ;)

> So if you have some time to play with this, could you please try the 
> following experiment. Put the following line into your 
> /etc/rc.d/rc.local file:
> 
>  echo 2 > /sys/kernel/uids/`grep -w dnetc /etc/passwd | cut -d: -f3`/cpu_share
>
> with group scheduling (CONFIG_FAIR_GROUP_SCHED=y) enabled. Also apply 
> the patch attached below as well - which fixes some interactivity 
> problems with group scheduling.
> Could you try that kernel and compare it to a FAIR_GROUP_SCHED-disabled 
> kernel's interactivity, and send us your observations?

With the patch and the sysfs-option my system works ok and last but not least
with the expected behaviour compared to a previous kernel.

In addition my first impression is that its responseness is better compared to
previous kernel versions and nearly the same compared to a kernel without
FAIR_GROUP_SCHED .

Compared to kernel 2.6.23 the 1-liner "time factor 819734028463158891" needs
now ~5.61 sec which is a little bit higher than the previous value of 5.44 sec.

Thanks for the solution (BTW b/c FAIR_GROUP_SCHED defaults to "y" I could bet
that more peoples run into this case).

-- 
MfG/Sincerely

Toralf Förster
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