Re: Endless "reclaiming chunk"/"relocating block group"

[Christoph Biedl <linux-kernel.bfrz@manchmal.in-ulm.de>]

Thanks for add the toughts shared ...

Zygo Blaxell wrote...

(...)
> It makes me think of possible rounding errors (e.g. the threshold
> calculation divides by 100, or there's a sum of quantities that leads
> to a percentage > 100, but the code treats zero as a special case and
> bails out long before, so I don't see how we'd reach those corner cases.

Out of desperation, I followed an approach I could read between the lines
here. The thing I did not mention (just because I forgot about it) is
the compiler version used to build the kernel. For reasons, this is
still a gcc-5 (5.4.0, to be precise). After a rebuild using gcc-11,
things are nice and smooth.

Now I cannot deny I'm quite confused. Assuming this is really the cause,
how should I go from here? I can patch the sources at will, but it's a
huge amount of code, and I don't even know where is start. Also from
expericence, debug print statements do bar the optimizer from creating
the problematic instructions.

    Christoph

FWIW, according to Documentation/process/changes.rst, that old gcc-5 is
considered sufficient. I didn't expect that :)