Message-Id: <6.2.1.2.2.20050516180151.04bc1eb0@mail.tekno-soft.it>
Date: Mon, 16 May 2005 18:37:50 +0200
To: William Lee Irwin III <wli@holomorphy.com>
From: Roberto Fichera <kernel@tekno-soft.it>
Subject: Re: How to use memory over 4GB
Cc: Michael Tokarev <mjt@tls.msk.ru>, linux-kernel@vger.kernel.org
In-Reply-To: <20050516155422.GM9304@holomorphy.com>
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At 17.54 16/05/2005, William Lee Irwin III wrote:
>At 17.10 16/05/2005, William Lee Irwin III wrote:
> >> This approach has already been used in production by various major
> >> applications and is even obsolete, now replaced by remap_file_pages()
> >> (in Linux), where it and its counterparts in other operating systems
> >> have been in use in production by various major applications for some 
> time.
> >> remap_file_pages() allows virtual pages in an mmap() area to correspond
> >> in an unrestricted fashion to the pages of the underlying file, and to
> >> alter this correspondence at will.
> >> In particular, Oracle's "vlm" option does this.
>
>On Mon, May 16, 2005 at 05:47:31PM +0200, Roberto Fichera wrote:
> > So, you are suggesting to create one big tmpfs area, 6GB for example, than
> > mmap() it to the user process and use the remap_file_pages() for all
> > the objects I want make "addressable" on the user process taking care
> > the return value of -1 which implies to munmap() something to free vm 
> space?
>
>I don't have any specific suggestion regarding layout or usage patterns
>besides pointing to remap_file_pages() being significantly lighter-weight
>than mmap() for the purposes of virtual windowing. The other aspects of
>all this (and even the use of remap_file_pages() at all) are, of course,
>at your own discretion. It is, however, notable that Oracle has had some
>success with a tactic similar to what you describe, where few objects are
>used and the application instead manages space within the objects
>dedicated to various purposes.
>
>In general, I'd recommend experimenting with different strategies to see
>which works best for you. This is all rather vague, and the mechanics of
>getting all this working with your application are sure to have enough
>alternative implementations to merit some decision-making and the like.

Thanks to pointing me to another solution, I will start to experimenting 
very soon :-)!


>-- wli
>-
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Roberto Fichera. 

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