Subject: Re: [PATCH] ppc44x: support for 256K PAGE_SIZE

From: Yuri Tikhonov <[email-masked]>
Date: Mon, 22 Oct 2007 20:12:20 +0400

On Friday 19 October 2007 17:24, Kumar Gala wrote:
> 
> On Oct 18, 2007, at 6:21 PM, Paul Mackerras wrote:
> 
> > Yuri Tikhonov writes:
> >
> >> The following patch adds support for 256KB PAGE_SIZE on ppc44x- 
> >> based boards.
> >> The applications to be run on the kernel with 256KB PAGE_SIZE have  
> >> to be
> >> built using the modified version of binutils, where the MAXPAGESIZE
> >> definition is set to 0x40000 (as opposite to standard 0x10000).
> >
> > Have you measured the performance using a 64kB page size?  If so, how
> > does it compare with the 256kB page size?
> 
> I was wondering about this as well?  Isn't this technically in  
> violation of the ABI?

 No it isn't the violation.

 As stated in "System V ABI. PowerPC processor supplement"
(on which the "Linux Standard Base Core Specification for PPC32"
is based): " ... Virtual addresses and file offsets for the PowerPC processor family 
segments are congruent modulo 64 Kbytes (0x10000) or larger powers of 2...".

 So, 256 Kbytes is just a larger case.

-- 
Yuri Tikhonov, Senior Software Engineer
Emcraft Systems, www.emcraft.com