linux-kernel - Re: Linux 2.6.39-rc3

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Message-ID: <4DA655E7.3000904@zytor.com>
Date:	Wed, 13 Apr 2011 19:03:19 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Yinghai Lu <yinghai@...nel.org>, Joerg Roedel <joro@...tes.org>,
	Ingo Molnar <mingo@...e.hu>,
	Alex Deucher <alexdeucher@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	dri-devel@...ts.freedesktop.org,
	Thomas Gleixner <tglx@...utronix.de>, Tejun Heo <tj@...nel.org>
Subject: Re: Linux 2.6.39-rc3

On 04/13/2011 04:39 PM, Linus Torvalds wrote:
> 
>  - Choice #2: understand exactly _what_ goes wrong, and fix it
> analytically (ie by _understanding_ the problem, and being able to
> solve it exactly, and in a way you can argue about without having to
> resort to "magic happens").
> 
> Now, the whole analytic approach (aka "computer sciency" approach),
> where you can actually think about the problem without having any
> pesky "reality" impact the solution is obviously the one we tend to
> prefer. Sadly, it's seldom the one we can use in reality when it comes
> to things like resource allocation, since we end up starting off with
> often buggy approximations of what the actual hardware is all about
> (ie broken firmware tables).
> 
> So I'd love to know exactly why one random number works, and why
> another one doesn't. But as long as we do _not_ know the "Why" of it,
> we will have to revert.
> 

Yes.  However, even if we *do* revert (and the time is running short on
not reverting) I would like to understand this particular one, simply
because I think it may very well be a problem that is manifesting itself
in other ways on other systems.

The other thing that this has uncovered is that we already have a bunch
of complete b*llsh*t magic numbers in this path, some of which are
trivially shown to be wrong or at least completely arbitrary, so there
are more issues here :(

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.
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