Re: [Bug #11342] Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c - bisected

Greg Ungerer
2008-08-28T00:06:21Z

Jamie Lokier wrote:
> Bernd Petrovitsch wrote:
>>> 32MB no-MMU ARM boards which people run new things and attach new
>>> devices to rather often - without making new hardware. Volume's too
>>> low per individual application to get new hardware designed and made.
>> Yes, you may have several products on the same hardware with somewhat
>> differing requirements (or not). But that is much less than a general
>> purpose system IMHO.
>
> It is, but the idea that small embedded systems go through a 'all
> components are known, drivers are known, test and if it passes it's
> shippable' does not always apply.
>
>>> I'm seriously thinking of forwarding porting the 4 year old firmware
>>> from 2.4.26 to 2.6.current, just to get new drivers and capabilities.
>> That sounds reasonable (and I never meant maintaining the old system
>> infinitely.
>
> Sounds reasonable, but it's vetoed for anticipated time and cost,
> compared with backporting on demand. Fair enough, since 2.6.current
> doesn't support ARM no-MMU last I heard ('soon'?).
>
> On the other hand, the 2.6 anti-fragmentation patches, including
> latest SLUB stuff, ironically meant to help big machines, sound really
> appealing for my current problem and totally unrealistic to
> backport...
>
>> ACK. We avoid MMU-less hardware too - especially since there is enough
>> hardware with a MMU around.
>
> I can't emphasise enough how much difference MMU makes to Linux userspace.
>
> It's practically: MMU = standard Linux (with less RAM), have everything.
> No-MMU = lots of familiar 'Linux' things not available or break.

And lots of things work in the usual way...

Of course the flip side is that for people who have platforms
without MMU they can run something more than the mostly "toy"
like operating systems typically available. There are plenty of
problem domains that the non-MMU limitations are not a problem for.
(Yours doesn't sound like one of them :-)

Regards
Greg

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Greg Ungerer -- Chief Software Dude EMAIL: gerg@snapgear.com
Secure Computing Corporation PHONE: +61 7 3435 2888
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