From: Linus Torvalds <torvalds@linux-foundation.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andi Kleen <andi@firstfloor.org>,
linux@sandersweb.net, linux-kernel@vger.kernel.org,
the arch/x86 maintainers <x86@kernel.org>,
Andi Kleen <andi-suse@firstfloor.org>
Subject: Re: [BUG] x86 kenel won't boot under Virtual PC
Date: Mon, 8 Sep 2008 09:07:41 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.1.10.0809080857450.3117@nehalem.linux-foundation.org> (raw)
In-Reply-To: <48C54839.8050304@zytor.com>
On Mon, 8 Sep 2008, H. Peter Anvin wrote:
>
> The help text is indeed out of date. I did a patch yesterday to, among other
> things, update it; I also want to verify that we are disabling all options
> that can cause gcc or binutils to generate nopl's; I plan to push it today.
Peter.
The help text may be out of date because of changes to NOPL usage, but you
should ask yourself whether the change is actually a _good_ change.
IOW, I really don't see why you are pushing changing the help-text,
instead of just making the kernel work better.
The fact that some broken gcc/binutils versions may screw us over _anyway_
may well mean that we should just push back on _that_ change instead.
Quite frankly, from a user perspective, even a very _technical_ one,
please tell me what the advantage of not being fairly generic by default
is. Really.
Yes, there are some _big_ ISA issues where it is worth doing real static
code selection (as opposed to just instruction selection and scheduling
etc that still _works_ for everybody, but optimizes for certain
archtiectures).
So things like cmpxchg/xadd (for atomics) and cmov (for compiler-generated
code), and bswap (for networking) can really make a big difference, and
are not really realistic to do dynamically.
But NOPL? That's simply not _worth_ it being painful over.
And the fact is, the current help text describes
(a) the historical meaning (optimize for a specific architecture, but
don't make extreme choices that are bad for others)
(b) what people would generally _want_.
and I really don't think that changing the help text is the right solution
here. It may be "technically correct", but it is simply not user-friendly
or smart.
Linus
next prev parent reply other threads:[~2008-09-08 16:08 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-31 18:22 [BUG] x86 kenel won't boot under Virtual PC David Sanders
2008-08-31 18:47 ` Linus Torvalds
2008-08-31 19:27 ` Arjan van de Ven
2008-08-31 19:39 ` Linus Torvalds
2008-09-05 15:38 ` David Sanders
2008-09-05 16:15 ` Jan Beulich
2008-09-05 16:39 ` Linus Torvalds
2008-09-05 18:43 ` Ingo Molnar
2008-09-05 20:06 ` H. Peter Anvin
2008-09-05 19:08 ` Jeremy Fitzhardinge
2008-09-05 20:12 ` H. Peter Anvin
2008-09-05 16:30 ` Linus Torvalds
2008-09-05 17:55 ` Andi Kleen
2008-08-31 20:03 ` David Sanders
2008-09-01 20:23 ` David Sanders
2008-09-01 22:22 ` Linus Torvalds
2008-09-02 12:08 ` David Sanders
2008-09-02 18:12 ` Linus Torvalds
2008-09-02 18:44 ` David Sanders
2008-09-03 11:09 ` Peter Zijlstra
2008-09-03 11:20 ` David Sanders
[not found] ` <48C1C156.9080003@zytor.com>
2008-09-07 20:07 ` David Sanders
2008-09-07 23:22 ` David Sanders
2008-09-08 1:48 ` H. Peter Anvin
2008-09-08 2:49 ` David Sanders
2008-09-08 4:04 ` H. Peter Anvin
2008-09-08 9:42 ` Andi Kleen
2008-09-08 13:25 ` David Sanders
2008-09-08 15:09 ` Linus Torvalds
2008-09-08 15:23 ` Ingo Molnar
2008-09-08 15:36 ` H. Peter Anvin
2008-09-08 15:38 ` David Sanders
2008-09-08 15:38 ` H. Peter Anvin
2008-09-08 15:45 ` Andi Kleen
2008-09-08 15:43 ` H. Peter Anvin
2008-09-08 15:50 ` H. Peter Anvin
2008-09-08 15:50 ` Andi Kleen
2008-09-08 15:50 ` H. Peter Anvin
2008-09-08 15:57 ` Andi Kleen
2008-09-08 15:54 ` H. Peter Anvin
2008-09-08 16:07 ` Linus Torvalds [this message]
2008-09-08 16:13 ` H. Peter Anvin
2008-09-08 16:15 ` H. Peter Anvin
2008-09-08 16:26 ` David Sanders
2008-09-08 16:20 ` Linus Torvalds
2008-09-08 16:32 ` H. Peter Anvin
2008-09-08 17:02 ` Ingo Molnar
2008-09-08 16:34 ` david
2008-09-08 16:42 ` H. Peter Anvin
2008-09-08 18:51 ` david
2008-09-08 16:59 ` Linus Torvalds
2008-09-08 17:00 ` Andi Kleen
2008-09-08 17:04 ` Linus Torvalds
2008-09-08 17:08 ` H. Peter Anvin
2008-09-08 17:12 ` H. Peter Anvin
2008-09-08 17:41 ` Linus Torvalds
2008-09-08 17:38 ` Linus Torvalds
2008-09-08 17:59 ` H. Peter Anvin
2008-09-08 19:09 ` H. Peter Anvin
2008-09-08 22:42 ` Linus Torvalds
2008-09-08 17:18 ` Andi Kleen
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