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To: Hanna Linder <hannal@us.ibm.com>
Cc: lse-tech@lists.sf.et, linux-kernel@vger.kernel.org
Subject: Re: Minutes from Feb 21 LSE Call
References: <96700000.1045871294@w-hlinder>
From: ebiederm@xmission.com (Eric W. Biederman)
Date: 22 Feb 2003 17:42:53 -0700
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Hanna Linder <hannal@us.ibm.com> writes:

> 	LSE Con Call Minutes from Feb21
> 
> Minutes compiled by Hanna Linder hannal@us.ibm.com, please post
> corrections to lse-tech@lists.sf.net.
> 
> Object Based Reverse Mapping:
> (Dave McCracken, Ben LaHaise, Rik van Riel, Martin Bligh, Gerrit Huizenga)
> 

> 	Ben said none of the users have been complaining about 
> performance with the existing rmap.  Martin disagreed and said Linus, 
> Andrew Morton and himself have all agreed there is a problem.
> One of the problems Martin is already hitting on high cpu machines with 
> large memory is the space consumption by all the pte-chains filling up
> memory and killing the machine. There is also a performance impact of 
> maintaining the chains.

Note: rmap chains can be restricted to an arbitrary length, or an
arbitrary total count trivially. All you have to do is allow a fixed
limit on the number of people who can map a page simultaneously.

The selection of which chain to unmap can be a bit tricky but is
relatively straight forward.  Why doesn't someone who is seeing
this just hack this up?


Eric
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