On Wed, Apr 19, 2023 at 6:12 AM Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > > On Tue, Apr 18, 2023 at 03:05:57PM -0700, Andrew Morton wrote: > > 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. > > That's fine by me. I have a slight preference to drop EXPERT and keep > the ranges in, especially if it affects current distro kernels. Debian > seems to enable EXPERT already in their arm64 kernel config but I'm not > sure about the Fedora or other distro kernels. If they don't, we can > fix/revert this Kconfig entry once the merging window is closed. Fedora and RHEL do not enable EXPERT already. Justin
