From: Balbir Singh <bsingharora@gmail.com>
To: Rashmica Gupta <rashmicy@gmail.com>, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH V2] powerpc/Kconfig: Update config option based on page size.
Date: Fri, 19 Feb 2016 17:07:53 +1100 [thread overview]
Message-ID: <56C6B139.8000605@gmail.com> (raw)
In-Reply-To: <1455860327-22913-1-git-send-email-rashmicy@gmail.com>
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 <rashmicy@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 <bsingharora@gmail.com>
Balbir Singh
next prev parent reply other threads:[~2016-02-19 6:07 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-19 5:38 [PATCH V2] powerpc/Kconfig: Update config option based on page size Rashmica Gupta
2016-02-19 6:07 ` Balbir Singh [this message]
2016-04-11 12:35 ` [V2] " Michael Ellerman
2016-04-19 14:59 ` Aneesh Kumar K.V
2016-04-19 23:09 ` Balbir Singh
2016-09-14 10:40 ` santhosh
2016-09-15 23:26 ` Michael Ellerman
2016-09-16 6:03 ` Balbir Singh
2016-09-16 15:16 ` Aneesh Kumar K.V
2016-09-19 7:15 ` Balbir Singh
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