Highmem on PPC?

Val Henson val at nmt.edu
Wed Feb 6 06:42:14 EST 2002

On Tue, Feb 05, 2002 at 08:33:16PM +0100, Benjamin Herrenschmidt wrote:
> >I'm currently getting hard crashes on the dual 7410 with highmem.  Not
> >even the SMI starts xmon.  I'm not sure that it's a software bug,
> >which is why I'm getting the dual 7450.
> Interesting. I have similar reports about dual 800s with 1.5G of RAM.
> I don't personally have a machine with that much RAM, so it makes things
> a bit difficult to debug. All I noticed so far is that
> enabling interrupt distribution will cause occasional lockups on my
> dual 7400 at work (not related to highmem). So if you plan to chase
> this highmem bug, start by disabling that option to avoid mixing
> problems.

I don't use interrupt distribution.

I triggered the absolute hard hang with my usual tests: 5 or 6 of the
following running in the background:

find /mnt/cdrom -exec cat {} \; > /dev/null 2>&1 &
find /usr -exec cat {} \; > /dev/null 2>&1 &

And a make -j8 zImage in the foreground.  I didn't even start the
flood ping before it hung. :)

> Just in case it's a spinlock bug (who knows...) you may want to hack
> the spinlock debug output to use the btext engine (basically #define
> printf to xmon_printf in the spinlock code and hack xmon/start.c to
> force use_screen).

This is actually over serial console, but I'll keep that in mind when
I get the apple.

> And let me know if you find something ;)

:) You bet.  You're sure you're not seeing these hangs?  What are you
using, dual 7400 with 1 GB RAM?


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