Increasing virtual address space of a process, by treating virtual address's as offsets in secondary memory.

Increasing virtual address space of a process, by treating virtual address's as offsets in secondary memory.

[vamsi krishna]

Hello Alan, mm-hackers,

I have been working this idea of increasing virtual address space of a
process with the help of secondary memory. At first this may seem like
the same virtual memory concept but its not the case.

Imagine all the virtual address the compiler generates while creating
the binary as relocatable offsets on the disk, and the application
specific runtime mmaps and munmaps these dynamically.

I was searching a lot about work on this, and found your reply where
you say that we can increase the virtual address space by mmaping and
munmaping programatically ourself.

So is the bigmem kernel implement this? may be  you can give me some
insight into this.

Some inputs on this would be highly appreciated.

Sincerely,
Vamsi kundeti. 

PS: Please refer this kernel mailing list email.


<--------------------------------------------------SNIP--------------------------------------------------------------------------->
Re: BIGMEM kernel question
From: Alan Cox (alan@lxorguk.ukuu.org.uk)
Date: Fri Jul 06 2001 - 16:46:16 EST



> Ahh. That makes sense. So how can I change the chunk size from 64k to
> something higher (I assume I could set it to 128k to effectively double
> that 3GB to 6GB)?

I think you misunderstand. If you want more than 3Gb you will have to map and
unmap stuff yourself. You only have 3Gb of per process address space due to
x86 weaknesses (lack of seperate kernel/user spaces without tlb flush
overhead nightmares)

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<------------------------------------------------------SNIP----------------------------------------------------------------------------->

Re: Increasing virtual address space of a process, by treating virtual address's as offsets in secondary memory.

[Alan Cox]

On Llu, 2005-07-18 at 10:12 +0530, vamsi krishna wrote:
> I was searching a lot about work on this, and found your reply where
> you say that we can increase the virtual address space by mmaping and
> munmaping programatically ourself.

Its something a few giant applications do with data sets and the trick
of using shared memory segments works on most Linux or Unixlike systems.
It's almost a historical note now. With 64bit processors its no longer
worth the pain