On Wed, 12 Apr 2023 18:27:08 +0100 Catalin Marinas <catalin.marinas@xxxxxxx> wrote:
It sounds nice in theory. In practice. EXPERT hides too much. When you
flip expert, you expose over a 175ish new config options which are
hidden behind EXPERT. You don't have to know what you are doing just
with the MAX_ORDER, but a whole bunch more as well. If everyone were
already running 10, this might be less of a problem. At least Fedora
and RHEL are running 13 for 4K pages on aarch64. This was not some
accidental choice, we had to carry a patch to even allow it for a
while. If this does go in as is, we will likely just carry a patch to
remove the "if EXPERT", but that is a bit of a disservice to users who
might be trying to debug something else upstream, bisecting upstream
kernels or testing a patch. In those cases, people tend to use
pristine upstream sources without distro patches to verify, and they
tend to use their existing configs. With this change, their MAX_ORDER
will drop to 10 from 13 silently. That can look like a different
issue enough to ruin a bisect or have them give bad feedback on a
patch because it introduces a "regression" which is not a regression
at all, but a config change they couldn't see.
If we remove EXPERT (as prior to this patch), I'd rather keep the ranges
and avoid having to explain to people why some random MAX_ORDER doesn't
build (keeping the range would also make sense for randconfig, not sure
we got to any conclusion there).
Well this doesn't seem to have got anywhere. I think I'll send the
patchset into Linus for the next merge window as-is. Please let's take
a look at this Kconfig presentation issue during the following -rc
cycle.
