linux-kernel - Re: [patch] CFS scheduler, -v8

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Message-ID: <20070511191824.GA7135@ucw.cz>
Date:	Fri, 11 May 2007 19:18:25 +0000
From:	Pavel Machek <pavel@....cz>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Peter Williams <pwil3058@...pond.net.au>,
	Esben Nielsen <nielsen.esben@...glemail.com>,
	Ingo Molnar <mingo@...e.hu>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Con Kolivas <kernel@...ivas.org>,
	Nick Piggin <npiggin@...e.de>, Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>, caglar@...dus.org.tr,
	Willy Tarreau <w@....eu>,
	Gene Heskett <gene.heskett@...il.com>, Mark Lord <lkml@....ca>,
	Zach Carter <linux@...hcarter.com>,
	buddabrod <buddabrod@...il.com>
Subject: Re: [patch] CFS scheduler, -v8

Hi!

> > Also notice that current cpus were not designed to work 300 years.
> > When we have hw designed for 50 years+, we can start to worry.
> 
> Indeed. CPU manufacturers don't seem to talk about it very much, and 
> searching for it with google on intel.com comes up with
> 
> 	The failure rate and Mean Time Between Failure (MTBF) data is not 
> 	currently available on our website. You may contact Intel? 
> 	Customer Support for this information.
> 
> which seems to be just a fancy way of saying "we don't actually want to 
> talk about it". Probably not because it's actually all that bad, but 
> simply because people don't think about it, and there's no reason a CPU 
> manufacturer would *want* people to think about it.
> 
> But if you wondered why server CPU's usually run at a lower frequency, 
> it's because of MTBF issues. I think a desktop CPU is usually specced to 
> run for 5 years (and that's expecting that it's turned off or at least 
> idle much of the time), while a server CPU is expected to last longer and 
> be active a much bigger percentage of time.
> 
> ("Active" == "heat" == "more damage due to atom migration etc". Which is 
> part of why you're not supposed to overclock stuff: it may well work well 
> for you, but for all you know it will cut your expected CPU life by 90%).

Actually, when I talked with AMD, they told me that cpus should last
10 years *at their max specced temperature*... which is 95Celsius. So
overclocking is not that evil, according to my info.

(That would mean way more than 10 years if you use your cpu
'normally'.)

But I guess capacitors from cpu power supply will hate you running cpu
at 95C...
							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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