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Date:      Thu, 03 Apr 1997 14:32:16 +0500
From:      "A JOSEPH KOSHY" <koshy@india.hp.com>
To:        "Peter M. Chen" <pmchen@eecs.umich.edu>
Cc:        freebsd-current@freebsd.org
Subject:   Re: question on buffer cache and VMIO 
Message-ID:  <199704030932.AA060449937@fakir.india.hp.com>
In-Reply-To: Your message of "Tue, 01 Apr 1997 22:15:03 EST."

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>>>> ""Peter M. Chen"" <pmchen@eecs.umich.edu> writes

> The only hardware is a battery.  The VM write protection is software.
> Those without batteries need to write to disk (or non-volatile memory);
> those with batteries (e.g. machine rooms, laptops) can keep data in memory
> if it survives crashes.

If I understood the paper correctly, Vista first copies out the protected 
address range to RIO protected memory prior to allowing the application
to proceed with its changes.

Would some form of copy-on-write scheme help to eliminate this initial
copy?  Whether there would be a performance benefit from this would depend
on the relative costs of copying vs creating a set of mappings, I guess.

Koshy
<koshy@india.hp.com>			My Personal Opinions Only



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