On Thu, 2012-03-29 at 13:12 +0100, Simon McVittie wrote:
> On Thu, 29 Mar 2012 at 13:30:54 +0200, Jelle de Jong wrote:
> > When will there be a non pea 3.x kernel like with the 2.6 kernel
> > available in Debian?
>
> >From the kernel changelog:
>
> * [i386] Rename '686-bigmem' flavour to '686-pae'; remove '686' flavour.
> For 686-class systems without PAE, the '486' flavour is more efficient
> than the '686' flavour due to optimisation for uniprocessor systems.
>
> So you should use the -486 flavour on non-PAE hardware. Larger numbers
> aren't necessarily better :-)
>
> Perhaps the linux-image-686 transitional package should depend on
> linux-image-486 (the conservative/safe/lowest-common-denominator choice).
The transitional packages linux-image-686 and linux-image-2.6-686
include a config script that will abort and explain the situation if the
system does not have PAE. Jelle apparently didn't install one of them.
(It's a shame that Linux doesn't check CPU flags and print an explicit
error message at boot time, but I think there's a bootstrap problem
there. It won't have a proper console driver available until after it's
set up page tables, so you wouldn't see the message unless you set
earlyprintk.)
> On the other hand, linux-image-686-pae (the former "bigmem" version) is
> more appropriate for most mainstream CPUs (although not for unusual CPUs like
> your Geode), which is presumably the reason why automatic migration
> from -686 is to that one.
I think that the large majority of systems using the '686' flavour have
PAE. Many (most?) are SMP so the '486' flavour would be a large
regression.
> The kernel team's advice on the appropriate new kernel for various CPUs
> should probably go in the wheezy release notes, particularly if cases
> like this exist.
There should perhaps be a note about upgrading so that users who need to
switch from 686 to 486 can do that at the start of the upgrade (avoiding
an error in the middle). For any other upgrade and new installations,
It Just Works.
Ben.
--
Ben Hutchings
Horngren's Observation:
Among economists, the real world is often a special case.
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