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Date: Sun, 2 Dec 2007 23:20:40 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Andi Kleen <andi@firstfloor.org>
Cc: Arjan van de Ven <arjan@infradead.org>, linux-kernel@vger.kernel.org,
       Andrew Morton <akpm@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [feature] automatically detect hung TASK_UNINTERRUPTIBLE tasks
Message-ID: <20071202222040.GA31707@elte.hu>
References: <20071201092037.GA32544@elte.hu> <p737ijwylet.fsf@bingen.suse.de> <20071202185945.GA25990@elte.hu> <20071202114152.3bf4332d@laptopd505.fenrus.org> <20071202200953.GA23994@one.firstfloor.org> <20071202202602.GA16480@elte.hu> <20071202204725.GA25891@one.firstfloor.org> <20071202211027.GA32282@elte.hu> <20071202211925.GA26414@one.firstfloor.org>
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* Andi Kleen <andi@firstfloor.org> wrote:

> > Until now users had little direct recourse to get such problems 
> > fixed. (we had sysrq-t, but that included no real metric of how long 
> > a task was
> 
> Actually task delay accounting can measure this now.  iirc someone had 
> a latencytop based on it already.

Delay accounting (or the /proc/<PID>/sched fields that i added recently) 
only get updated once a task has finished its unreasonably long delay 
and has scheduled. So lockups or extremely long delays _wont be 
detected_ this way. This is a debugging facility that clearly belongs 
into the kernel. Your arguments just make no objective sense.

	Ingo
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