Re: [PATCH 02/14] arm64: drop ranges in definition of ARCH_FORCE_MAX_ORDER

Catalin Marinas
2023-03-23T10:15:33Z

On Thu, Mar 23, 2023 at 11:21:44AM +0200, Mike Rapoport wrote:
> From: "Mike Rapoport (IBM)" <rppt@kernel.org>
>
> It is not a good idea to change fundamental parameters of core memory
> management. Having predefined ranges suggests that the values within
> those ranges are sensible, but one has to *really* understand
> implications of changing MAX_ORDER before actually amending it and
> ranges don't help here.
>
> Drop ranges in definition of ARCH_FORCE_MAX_ORDER
>
> Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
> ---
> arch/arm64/Kconfig | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index e60baf7859d1..bab6483e4317 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1489,9 +1489,7 @@ config XEN
> config ARCH_FORCE_MAX_ORDER
> int "Maximum zone order" if ARM64_4K_PAGES || ARM64_16K_PAGES
> default "13" if ARM64_64K_PAGES
> - range 11 13 if ARM64_16K_PAGES
> default "11" if ARM64_16K_PAGES
> - range 10 15 if ARM64_4K_PAGES
> default "10"

I don't mind rewriting the help text as in the subsequent patch but I'd
keep the ranges as a safety measure. It's less wasted time explaining to
people why some random max order doesn't work. Alternatively, we can
drop the ranges but make this option configurable only if EXPERT.

--
Catalin