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Old 01-27-2009, 01:35 PM
Scott James Remnant
 
Default LP#74179 -- support for i386 machines with >3GB RAM

On Tue, 2009-01-27 at 13:51 +0000, Andy Whitcroft wrote:

> Therefore I am proposing we create a new i386 only flavour generic64g
> which is identicle to the generic flavour except that it enables PAE and
> options that that requires.
>
What are the downsides of just enabling PAE in the generic kernel?

Scott
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Old 01-27-2009, 03:02 PM
Scott James Remnant
 
Default LP#74179 -- support for i386 machines with >3GB RAM

On Tue, 2009-01-27 at 16:37 +0100, Stefan Bader wrote:

> Scott James Remnant wrote:
> > On Tue, 2009-01-27 at 13:51 +0000, Andy Whitcroft wrote:
> >
> >> Therefore I am proposing we create a new i386 only flavour generic64g
> >> which is identicle to the generic flavour except that it enables PAE and
> >> options that that requires.
> >>
> > What are the downsides of just enabling PAE in the generic kernel?
>
> The downside is that CPUs without PAE support do not boot. And that are still
> some around.
>
Which CPUs, specifically?

Do they not boot, or just not address areas of memory?

Is there no way for the kernel to detect this like it does with just
about every other CPU feature and disable it on the fly?

Scott
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Old 01-27-2009, 04:46 PM
Scott James Remnant
 
Default LP#74179 -- support for i386 machines with >3GB RAM

On Tue, 2009-01-27 at 17:09 +0100, Ante Karamatic wrote:

> On Tue, 27 Jan 2009 16:02:27 +0000
> Scott James Remnant <scott@canonical.com> wrote:
>
> > Which CPUs, specifically?
>
> Wikipedia [http://en.wikipedia.org/wiki/Physical_Address_Extension]:
>
This says:

As of 2008[update], many common Linux distributions come with a
PAE-enabled kernel as the distribution-specific default.

Mac OS X for Intel Macs supports PAE and the NX bit on all CPUs
supported by Apple

Solaris supports PAE beginning with Solaris version 7

Windows XP SP2 and later, by default, on processors with the no-execute
(NX) or execute-disable (XD) feature, runs in PAE mode in order to allow
NX


This sounds like PAE is widely enabled, and people who are going to be
bitten by no PAE are firmly in the special group who can compile their
own kernel to turn it off.

Scott
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Old 01-27-2009, 05:52 PM
Andy Whitcroft
 
Default LP#74179 -- support for i386 machines with >3GB RAM

On Tue, Jan 27, 2009 at 07:38:46AM -0700, Tim Gardner wrote:

> I am not in favor of another flavor. Despite the reluctance of some
> folks to use the server flavour, it _does_ solve their use case with no
> effort on our part. If these users are that sensitive to the
> optimization differences between generic and server, then they'll have
> to run a 64 bit kernel.
>
> My goal is to actually reduce the i386 flavours for Jaunty+1 to just
> generic. Hardy should be the last LTS that supports a 32 bit server.

Then if we plan on having just one flavour in N+1 that would have to be
PAE enabled.

I thought the issue there was that some older h/w doesn't support PAE
necessarily (i want to say lpia is in this situation though am not sure
why) so we would end up needing an PAE and non-PAE build still?

-apw

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Old 01-27-2009, 05:53 PM
Andy Whitcroft
 
Default LP#74179 -- support for i386 machines with >3GB RAM

On Tue, Jan 27, 2009 at 02:35:55PM +0000, Scott James Remnant wrote:
> On Tue, 2009-01-27 at 13:51 +0000, Andy Whitcroft wrote:
>
> > Therefore I am proposing we create a new i386 only flavour generic64g
> > which is identicle to the generic flavour except that it enables PAE and
> > options that that requires.
> >
> What are the downsides of just enabling PAE in the generic kernel?

I think there is some Intel variants we support which do not support it.

-apw

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Old 01-27-2009, 05:54 PM
Andy Whitcroft
 
Default LP#74179 -- support for i386 machines with >3GB RAM

On Tue, Jan 27, 2009 at 03:28:46PM +0100, Ante Karamatic wrote:
> On Tue, 27 Jan 2009 13:51:32 +0000
> Andy Whitcroft <apw@canonical.com> wrote:
>
> > Therefore I am proposing we create a new i386 only flavour generic64g
> > which is identicle to the generic flavour except that it enables PAE
> > and options that that requires.
> >
> > Following this email is a patch implementing this for Jaunty.
> >
> > Comments?
>
> I don't think people will understand what generic64g means (think of
> linux-generic, linux-server and linux-generic64g; what's 64g?[1]). Sure,

Yeah the name could well be better. I was staying away from things with
- and the like as they tend to go wrong. I wanted to get something out
for discussion and am happy to rework the name.

> they could read release notes or some how to, but naming it, for
> example, generic-bigmem would be self explanatory (maybe even just
> bigmem). Even linux-generic-pae would make more sense, since these days
> even lots of Windows users do know that 'PAE makes all memory
> available'.
>
> [1] at first, I didn't make the connection between generic64g and 64GB
> limit. I don't think it's wise to put limitations in the name of the
> package

-apw

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