Re: THP broken on OCTEON?

[Joshua Kinard <kumba@gentoo.org>]

On 05/23/2016 11:20, Ralf Baechle wrote:
> On Mon, May 23, 2016 at 06:13:46PM +0300, Aaro Koskinen wrote:
> 
>> I'm getting kernel crashes (see below) reliably when building Perl in
>> parallel (make -j16) on OCTEON EBH5600 board (8 cores, 4 GB RAM) with
>> Linux 4.6.
>>
>> It seems that CONFIG_TRANSPARENT_HUGEPAGE has something to do with the
>> issue - disabling it makes build go through fine.
>>
>> Any ideas?
> 
> I thought it was working except on SGI Origin 200/2000 aka IP27 where
> Joshua Kinard (added to cc) was hitting issues as well.
> 
> Joshua, does that similar to the issues you were hitting?
> 
>   Ralf

NAK, this issue looks completely different to IP30/IP27.  In this case, it
looks like the hardware is detecting the case where multiple TLB entries match
and it's killing the machine to avoid hardware damage.  I don't want to know
how the SGI systems handle this scenario (does the R10000 do a TLB shutdown??).

On IP30, using THP usually results in instruction bus errors (IBE), after a set
time, depending on the machine's configuration (<2GB RAM, virtually instant on
userland init; >2GB RAM, might survive for a few minutes, even getting all the
way to runlevel 3 randomly).

IP27 was somewhat similar to IP30, in that THP usually results in IBEs after a
few seconds of hitting userland bringup (bash is pretty quick at triggering an
IBE), but I haven't tried experimenting with varying the amount of RAM in that
machine, due to the fragility of pulling the nodeboards out constantly.  I also
haven't tried THP since refactoring/rewriting the IP27 code back in Feb to see
if I magically fixed it...

-- 
Joshua Kinard
Gentoo/MIPS
kumba@gentoo.org
6144R/F5C6C943 2015-04-27
177C 1972 1FB8 F254 BAD0 3E72 5C63 F4E3 F5C6 C943

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