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Re: Linux Shared Memory Issue

To: Atsushi Nemoto <nemoto@toshiba-tops.co.jp>
Subject: Re: Linux Shared Memory Issue
From: Jun Sun <jsun@mvista.com>
Date: Thu, 25 Apr 2002 11:46:04 -0700
Cc: turcotte@broadcom.com, linux-mips@oss.sgi.com, mturc@broadcom.com
References: <NDBBKEAAOJECIDBJKLIHOEDDCDAA.turcotte@broadcom.com> <3CC72BA3.90600@mvista.com> <20020425.142518.85417141.nemoto@toshiba-tops.co.jp>
Sender: owner-linux-mips@oss.sgi.com
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:0.9.2.1) Gecko/20010901
Atsushi Nemoto wrote:

On Wed, 24 Apr 2002 15:03:15 -0700, Jun Sun <jsun@mvista.com> said:

jsun> Looks like the infamous cache aliasing problem.  Steve
jsun> Longerbeam had a patch which may help.  Please try it and let me
jsun> know the results.

jsun> +#define COLOUR_ALIGN(addr)    (((addr)+SHMLBA-1)&~(SHMLBA-1))

Recent sparc64's COLOUR_ALIGN macro have pgoff argument like this.
We should do it same way for MIPS?

#define COLOUR_ALIGN(addr,pgoff)                \
        ((((addr)+SHMLBA-1)&~(SHMLBA-1)) +  \
         (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1)))



What is the purpose of adding the pgoff part? To avoid mapping all shared regions into the beginning of cache?

Jun


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