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Re: page size change on MIPS

To: David Daney <ddaney@caviumnetworks.com>
Subject: Re: page size change on MIPS
From: Himanshu Aggarwal <lkml.himanshu@gmail.com>
Date: Sun, 30 Jan 2011 20:32:43 +0530
Cc: naveen yadav <yad.naveen@gmail.com>, kernelnewbies@nl.linux.org, linux-mips@linux-mips.org
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On Tue, Jan 25, 2011 at 12:26 AM, David Daney <ddaney@caviumnetworks.com> wrote:
> On 01/24/2011 07:02 AM, naveen yadav wrote:
>> Hi All,
>>
>>
>> we are using mips32r2  so I want to know which all pages size it can support?
>> When I modify arch/mips/Kconfig.  it boot sucessfully on 16KB page
>> size. but hang/not boot crash when change page size to 8KB,32KB and 64
>> KB.
>
> I don't think 8KB and 32KB work on most mips32r2 processors.  You would
> have to check the processor manual to be sure.
>
>
>>
>> We are using 2.6.30 kernel.
>>
>> At Page Size 8KB and 32KB  it hang in unpack_to_rootfs() function of
>> init/initramfs.c
>>
>> 64KB it hangs when execute init  Kernel panic - not syncing: Attempted
>> to kill init!
>
> I regularly run 4K, 16K, and 64K page sizes with a Debian rootfs.  If
> you run with a broken uClibc toolchain that doesn't support larger
> pages, it will of course fail.  In this case the problem is with your
> toolchain, not the kernel.
>
> David Daney
>
>
>>
>> config PAGE_SIZE_4KB
>>          bool "4kB"
>>          help
>>           This option select the standard 4kB Linux page size.  On some
>>           R3000-family processors this is the only available page size. 
>>  Using
>>           4kB page size will minimize memory consumption and is therefore
>>           recommended for low memory systems.
>>
>> config PAGE_SIZE_8KB
>>          bool "8kB"
>>         depends on (EXPERIMENTAL&&  CPU_R8000) || CPU_CAVIUM_OCTEON
>>          help
>>            Using 8kB page size will result in higher performance kernel at
>>            the price of higher memory consumption.  This option is available
>>            only on R8000 and cnMIPS processors.  Note that you will need a
>>            suitable Linux distribution to support this.
>>
>> config PAGE_SIZE_16KB
>>          bool "16kB"
>>         depends on !CPU_R3000&&  !CPU_TX39XX
>>          help
>>            Using 16kB page size will result in higher performance kernel at
>>            the price of higher memory consumption.  This option is available 
>> on
>>            all non-R3000 family processors.  Note that you will need a 
>> suitable
>>            Linux distribution to support this.
>>
>> config PAGE_SIZE_32KB
>>          bool "32kB"
>>          help
>>            Using 32kB page size will result in higher performance kernel at
>>            the price of higher memory consumption.  This option is available
>>            only on cnMIPS cores.  Note that you will need a suitable Linux
>>            distribution to support this.
>>
>> config PAGE_SIZE_64KB
>>          bool "64kB"
>>         depends on EXPERIMENTAL&&  !CPU_R3000&&  !CPU_TX39XX
>>          help
>>            Using 64kB page size will result in higher performance kernel at
>>            the price of higher memory consumption.  This option is available 
>> on
>>            all non-R3000 family processor.  Not that at the time of this
>>            writing this option is still high experimental.
>>
>>
>
>
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Why should the application or the toolchains depend on pagesize? I am
not very clear on this. Can someone explain it?

Regards,
Himanshu

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