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

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Date:	Tue, 24 Apr 2007 03:12:24 -0400
From:	Gene Heskett <gene.heskett@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Williams <pwil3058@...pond.net.au>,
	Arjan van de Ven <arjan@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Juliusz Chroboczek <jch@....jussieu.fr>,
	Con Kolivas <kernel@...ivas.org>, ck list <ck@....kolivas.org>,
	Bill Davidsen <davidsen@....com>, Willy Tarreau <w@....eu>,
	William Lee Irwin III <wli@...omorphy.com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Galbraith <efault@....de>,
	Thomas Gleixner <tglx@...utronix.de>, caglar@...dus.org.tr
Subject: Re: [REPORT] cfs-v4 vs sd-0.44

On Tuesday 24 April 2007, Ingo Molnar wrote:
>* Gene Heskett <gene.heskett@...il.com> wrote:
>> > Gene has done some testing under CFS with X reniced to +10 and the
>> > desktop still worked smoothly for him.
>>
>> As a data point here, and probably nothing to do with X, but I did
>> manage to lock it up, solid, reset button time tonight, by wanting
>> 'smart' to get done with an update session after amanda had started.
>> I took both smart processes I could see in htop all the way to -19,
>> but when it was about done about 3 minutes later, everything came to
>> an instant, frozen, reset button required lockup.  I should have
>> stopped at -17 I guess. :(
>
>yeah, i guess this has little to do with X. I think in your scenario it
>might have been smarter to either stop, or to renice the workloads that
>took away CPU power from others to _positive_ nice levels. Negative nice
>levels can indeed be dangerous.
>
>(Btw., to protect against such mishaps in the future i have changed the
>SysRq-N [SysRq-Nice] implementation in my tree to not only change
>real-time tasks to SCHED_OTHER, but to also renice negative nice levels
>back to 0 - this will show up in -v6. That way you'd only have had to
>hit SysRq-N to get the system out of the wedge.)
>
>	Ingo

That sounds handy, particularly with idiots like me at the wheel...


-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
When a Banker jumps out of a window, jump after him--that's where the money 
is.
		-- Robespierre
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