Re: [PATCH] MIPS: Increase range of CONFIG_FORCE_MAX_ZONEORDER

[Paul Cercueil]

Hi Thomas,

Le mar. 22 sept. 2020 à 18:02, Thomas Bogendoerfer 
<tsbogend@xxxxxxxxxxxxxxxx> a écrit :
> On Thu, Sep 17, 2020 at 03:35:28PM +0200, Paul Cercueil wrote:
> >  There is nothing that prevents us from using lower maximum values.
> >  It's something that we actually want, when using bigger page sizes 
> > on
> >  devices with low RAM.
> >
> >  Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> >  ---
> >   arch/mips/Kconfig | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> >  diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> >  index 632fe8fe68c4..dca2bbdbfc24 100644
> >  --- a/arch/mips/Kconfig
> >  +++ b/arch/mips/Kconfig
> >  @@ -2251,7 +2251,7 @@ config FORCE_MAX_ZONEORDER
> >   	default "13" if MIPS_HUGE_TLB_SUPPORT && PAGE_SIZE_32KB
> >   	range 12 64 if MIPS_HUGE_TLB_SUPPORT && PAGE_SIZE_16KB
> >   	default "12" if MIPS_HUGE_TLB_SUPPORT && PAGE_SIZE_16KB
> >  -	range 11 64
> >  +	range 0 64
>
> Do we need the range at all ? Most other archs don't use a range...

The maximum contiguous block size cannot be lower than a huge page, so 
that's why the 'range' are here.

Which makes me think that there should probably be a "range 11 64 if 
MIPS_HUGE_TLB_SUPPORT && PAGE_SIZE_8KB" and the same for 4KB pages.

With a lower value and huge pages enabled in the config, the kernel 
probably would not boot.

Cheers,
-Paul