On 19/02/16 16:38, Rashmica Gupta wrote: > Currently on PPC64 changing kernel pagesize from 4K to 64K leaves > FORCE_MAX_ZONEORDER set to 13 - which produces a compile error. > > The error occurs because of the following constraint (from > include/linux/mmzone.h) being violated: > > MAX_ORDER -1 + PAGESHIFT <= SECTION_SIZE_BITS. > > Expanding this out, we get: > > FORCE_MAX_ZONEBITS <= 25 - PAGESHIFT, > > which requires, for a 64K page, FORCE_MAX_ZONEBITS <= 9. Thus set max > value of FORCE_MAX_ZONEORDER for 64K pages to 9, and 4K pages to 13. > > Also, check the minimum value: > In include/linux/huge_mm.h, we have the constraint HPAGE_PMD_ORDER < > MAX_ORDER which expands out to: > > PTE_INDEX_SIZE < FORCE_MAX_ZONEORDER. > > PTE_INDEX_SIZE is: > 9 (4k hash or no hash 4K pgtable) or > 8 (64K hash or no hash 64K pgtable). > Thus a min value of 8 for 64K pages and 9 for 4K pages is reasonable. > > So, update the range of FORCE_MAX_ZONEORDER from 9-64 to 8-9 for 64K pages > and from 13-64 to 9-13 for 4K pages. > > Signed-off-by: Rashmica Gupta <rashm...@gmail.com> > --- > > v2: Changed the range for 4K pages and minimum for 64K pages as suggested > by Balbir Singh. > > > arch/powerpc/Kconfig | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index e4824fd04bb7..b933530821fb 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -585,9 +585,9 @@ endchoice > > config FORCE_MAX_ZONEORDER > int "Maximum zone order" > - range 9 64 if PPC64 && PPC_64K_PAGES > + range 8 9 if PPC64 && PPC_64K_PAGES > default "9" if PPC64 && PPC_64K_PAGES > - range 13 64 if PPC64 && !PPC_64K_PAGES > + range 9 13 if PPC64 && !PPC_64K_PAGES > default "13" if PPC64 && !PPC_64K_PAGES > range 9 64 if PPC32 && PPC_16K_PAGES > default "9" if PPC32 && PPC_16K_PAGES Reviewed-by: Balbir Singh <bsinghar...@gmail.com>
Balbir Singh _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
