Re: [PATCH 0/9] x86-64 put current in r10

Andi Kleen
2005-11-30T15:29:09Z

On Wed, Nov 30, 2005 at 05:18:47PM +0200, Matti Aarnio wrote:
> On Tue, Nov 29, 2005 at 11:21:18PM -0500, Benjamin LaHaise wrote:
> > Date: Tue, 29 Nov 2005 23:21:18 -0500
> > From: Benjamin LaHaise <bcrl@kvack.org>
> > To: Andi Kleen <ak@suse.de>
> > Cc: linux-kernel@vger.kernel.org
> > Subject: [PATCH 0/9] x86-64 put current in r10
> >
> > Hello Andi,
> >
> > The following emails contain the patches to convert x86-64 to store current
> > in r10 (also at http://www.kvack.org/~bcrl/patches/v2.6.15-rc3/). This
> > provides a significant amount of code savings (~43KB) over the current
> > use of the per cpu data area. I also tested using r15, but that generated
> > code that was larger than that generated with r10. This code seems to be
> > working well for me now (it stands up to 32 and 64 bit processes and ptrace
> > users) and would be a good candidate for further exposure.
>
> I would rather prefer NOT to introduce this at this time.
> My primary concern is that during "even numbered series" there
> should not be radical internal ABI/API changes, like this one.

Hmm? I am not aware of such a constraint.

It's not very invasive anyways in that it would require changing
a lot of code.

> In 2.7 it can be introduced, by all means.
>
> Indeed at the moment my thinking is, that X86-64 is way more UNSTABLE,
> than it should be. (And Linux kernel overall, but that is another story.)

The actual x86-64 kernel is actually quite stable, most of the reported
problems (including yours) come from various hardware or firmware
issues mostly in new platforms. If you use a trusty old chipset
(e.g. AMD 8111 or Intel E7505) and proven motherboard you're usually ok.

-Andi