* [PATCH] powerpc/Kconfig: Update config option based on page size.
@ 2016-02-19 1:55 Rashmica Gupta
2016-02-19 4:08 ` Balbir Singh
2016-02-19 8:15 ` Arnd Bergmann
0 siblings, 2 replies; 4+ messages in thread
From: Rashmica Gupta @ 2016-02-19 1:55 UTC (permalink / raw)
To: linuxppc-dev
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.
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 9 for 64K pages is reasonable.
So, update the range of FORCE_MAX_ZONEORDER from 9-64 to 9-9.
Signed-off-by: Rashmica Gupta <rashmicy@gmail.com>
---
arch/powerpc/Kconfig | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index e4824fd04bb7..3bd3465b93ba 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -585,7 +585,7 @@ endchoice
config FORCE_MAX_ZONEORDER
int "Maximum zone order"
- range 9 64 if PPC64 && PPC_64K_PAGES
+ range 9 9 if PPC64 && PPC_64K_PAGES
default "9" if PPC64 && PPC_64K_PAGES
range 13 64 if PPC64 && !PPC_64K_PAGES
default "13" if PPC64 && !PPC_64K_PAGES
--
2.5.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] powerpc/Kconfig: Update config option based on page size.
2016-02-19 1:55 [PATCH] powerpc/Kconfig: Update config option based on page size Rashmica Gupta
@ 2016-02-19 4:08 ` Balbir Singh
2016-02-19 4:31 ` Rashmica
2016-02-19 8:15 ` Arnd Bergmann
1 sibling, 1 reply; 4+ messages in thread
From: Balbir Singh @ 2016-02-19 4:08 UTC (permalink / raw)
To: Rashmica Gupta, linuxppc-dev
On 19/02/16 12:55, 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.
IA64 has this cool hack
12 #ifdef CONFIG_FORCE_MAX_ZONEORDER
13 #if ((CONFIG_FORCE_MAX_ZONEORDER - 1 + PAGE_SHIFT) > SECTION_SIZE_BITS)
14 #undef SECTION_SIZE_BITS
15 #define SECTION_SIZE_BITS (CONFIG_FORCE_MAX_ZONEORDER - 1 + PAGE_SHIFT)
16 #endif
But coming back (we can revisit the SECTION_SIZE_BITS definition later)
MAX_ORDER -1 + 16 <= 24 for 64 K
and
MAX_ORDER -1 + 12 < = 24 for 4K
Your calculations are correct
>
> 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.
>
> 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 9 for 64K pages is reasonable.
For 4K pages we end up with
9 < FORCE_MAX_ZONE_ORDER
FORCE_MAX_ZONE_ORDER -1 + 12 < = 24
The range is 9 to 13
For 64K we end up with
8 < FORCE_MAX_ZONE_ORDER
FORCE_MAX_ZONE_ORDER -1 + 16 <= 24 or FORCE_MAX_ZONE_ORDER <= 9
The range is really between 8 and 9 unless we tweak the SECTION_SIZE_BITS
> So, update the range of FORCE_MAX_ZONEORDER from 9-64 to 9-9.
>
> Signed-off-by: Rashmica Gupta <rashmicy@gmail.com>
> ---
> arch/powerpc/Kconfig | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index e4824fd04bb7..3bd3465b93ba 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -585,7 +585,7 @@ endchoice
>
> config FORCE_MAX_ZONEORDER
> int "Maximum zone order"
> - range 9 64 if PPC64 && PPC_64K_PAGES
> + range 9 9 if PPC64 && PPC_64K_PAGES
range 8 9?
> default "9" if PPC64 && PPC_64K_PAGES
> range 13 64 if PPC64 && !PPC_64K_PAGES
Should this be fixed as well?
range 9 13?
> default "13" if PPC64 && !PPC_64K_PAGES
Please check my calculations
Reviewed-by: Balbir Singh <bsingharora@gmail.com>
Balbir Singh
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] powerpc/Kconfig: Update config option based on page size.
2016-02-19 4:08 ` Balbir Singh
@ 2016-02-19 4:31 ` Rashmica
0 siblings, 0 replies; 4+ messages in thread
From: Rashmica @ 2016-02-19 4:31 UTC (permalink / raw)
To: Balbir Singh; +Cc: Michael Ellerman, linuxppc-dev
On 19/02/16 15:08, Balbir Singh wrote:
>
> On 19/02/16 12:55, 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.
> IA64 has this cool hack
>
> 12 #ifdef CONFIG_FORCE_MAX_ZONEORDER
> 13 #if ((CONFIG_FORCE_MAX_ZONEORDER - 1 + PAGE_SHIFT) > SECTION_SIZE_BITS)
> 14 #undef SECTION_SIZE_BITS
> 15 #define SECTION_SIZE_BITS (CONFIG_FORCE_MAX_ZONEORDER - 1 + PAGE_SHIFT)
> 16 #endif
>
> But coming back (we can revisit the SECTION_SIZE_BITS definition later)
I feel like someone more senior than me should weigh in on if this is
worth doing...
> MAX_ORDER -1 + 16 <= 24 for 64 K
>
> and
>
> MAX_ORDER -1 + 12 < = 24 for 4K
>
> Your calculations are correct
>> 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.
>>
>> 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 9 for 64K pages is reasonable.
> For 4K pages we end up with
>
> 9 < FORCE_MAX_ZONE_ORDER
> FORCE_MAX_ZONE_ORDER -1 + 12 < = 24
>
> The range is 9 to 13
>
> For 64K we end up with
> 8 < FORCE_MAX_ZONE_ORDER
> FORCE_MAX_ZONE_ORDER -1 + 16 <= 24 or FORCE_MAX_ZONE_ORDER <= 9
>
> The range is really between 8 and 9 unless we tweak the SECTION_SIZE_BITS
Yup, you are right! Might have had a brain spaz...
>> So, update the range of FORCE_MAX_ZONEORDER from 9-64 to 9-9.
>>
>> Signed-off-by: Rashmica Gupta <rashmicy@gmail.com>
>> ---
>> arch/powerpc/Kconfig | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index e4824fd04bb7..3bd3465b93ba 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -585,7 +585,7 @@ endchoice
>>
>> config FORCE_MAX_ZONEORDER
>> int "Maximum zone order"
>> - range 9 64 if PPC64 && PPC_64K_PAGES
>> + range 9 9 if PPC64 && PPC_64K_PAGES
> range 8 9?
Agreed.
>> default "9" if PPC64 && PPC_64K_PAGES
>> range 13 64 if PPC64 && !PPC_64K_PAGES
> Should this be fixed as well?
> range 9 13?
Agreed.
>> default "13" if PPC64 && !PPC_64K_PAGES
Should the default values remain as is, or follow the trend and be equal
to the minimum value?
> Please check my calculations
>
> Reviewed-by: Balbir Singh <bsingharora@gmail.com>
>
> Balbir Singh
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] powerpc/Kconfig: Update config option based on page size.
2016-02-19 1:55 [PATCH] powerpc/Kconfig: Update config option based on page size Rashmica Gupta
2016-02-19 4:08 ` Balbir Singh
@ 2016-02-19 8:15 ` Arnd Bergmann
1 sibling, 0 replies; 4+ messages in thread
From: Arnd Bergmann @ 2016-02-19 8:15 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Rashmica Gupta
On Friday 19 February 2016 12:55:43 Rashmica Gupta wrote:
>
> config FORCE_MAX_ZONEORDER
> int "Maximum zone order"
> - range 9 64 if PPC64 && PPC_64K_PAGES
> + range 9 9 if PPC64 && PPC_64K_PAGES
> default "9" if PPC64 && PPC_64K_PAGES
> range 13 64 if PPC64 && !PPC_64K_PAGES
> default "13" if PPC64 && !PPC_64K_PAGES
>
You can also use
int "Maximum zone order" if !PPC_64K_PAGES
which will hide the option in the case where no configuration is possible.
Arnd
^ permalink raw reply [flat|nested] 4+ messages in thread
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2016-02-19 1:55 [PATCH] powerpc/Kconfig: Update config option based on page size Rashmica Gupta
2016-02-19 4:08 ` Balbir Singh
2016-02-19 4:31 ` Rashmica
2016-02-19 8:15 ` Arnd Bergmann
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