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Re: Change of Default kernel page size i.e 4KB

To: naveen yadav <yad.naveen@gmail.com>
Subject: Re: Change of Default kernel page size i.e 4KB
From: Ralf Baechle <ralf@linux-mips.org>
Date: Wed, 1 Dec 2010 13:24:37 +0000
Cc: kernelnewbies@nl.linux.org, linux-arm-kernel@lists.arm.linux.org.uk, linux-mips@linux-mips.org
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On Wed, Dec 01, 2010 at 01:50:13PM +0530, naveen yadav wrote:

> Cc: kernelnewbies@nl.linux.org,
>       linux-arm-kernel-request@lists.arm.linux.org.uk,
                        ^^^^^^^^ WTF?
>       linux-mips@linux-mips.org

> I have few drivers and very big application running on ARM and MIPS target.
> I want to check the performance by changing the page size ie.
> 
> 8K, 16K, 32K etc.
> 
> Is it possile, If yes then what all care i need to take .

For MIPS: Rebuild kernel with support for the new kernel size.  Few MIPS
cores.  Note that the `odd´ page sizes, that those that aren't a power
of 4 are only supported by Cavium while all MIPS III and newer processors
support even `even´ sizes 4KB, 16KB and 64KB.

Aside of rebuilding the kernel you also need a suitable userland; older
versions of binutils will produce binaries that only run
for 4kB page sizes.

For ARM the page size is fixed at 4kB which will simplify your benchmarking
efforts ;)

Performance gains very much depends on the workload but in general larger
sizes are beneficial except maybe for systems with very little memory.

  Ralf

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