Message-Id: <6.2.1.2.2.20050516174053.07185270@mail.tekno-soft.it>
Date: Mon, 16 May 2005 17:47:31 +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: <20050516151023.GK9304@holomorphy.com>
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 <20050516151023.GK9304@holomorphy.com>
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At 17.10 16/05/2005, William Lee Irwin III wrote:

>On Mon, May 16, 2005 at 03:16:28PM +0200, Roberto Fichera wrote:
> > I was thinking to create as many object I need by the usual shm_open(),
> > than mmap() it on a process until I get ENOMEM. So, when I get a
> > ENOMEM I start to munmap() objects in order to free some user space
> > memory and create the needed space to complete mmap() for the
> > requested object.
>
>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.

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?


>-- wli

Roberto Fichera. 

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