Re: What is the truth about Linux 2.4's RAM limitations?

From: Ingo Oeser (
Date: Mon Jul 16 2001 - 03:37:03 EST

On Mon, Jul 09, 2001 at 11:01:51PM -0400, wrote:
> stack gets mapped into the top of memory at 0xc0000000 and it grows down
> tword the program text. Files or shared libraries are mmaped in starting
> at 0x40000000 (1G) and each new mmap() occurs at a higher address so that
> the mapped area grows tword the stack.
> its something like this:
> 0x00000000 ---> Unmapped
> 0x08048000 ---> Text/Data
> 0x40000000 ---> Shared libs and mmaped
> 0xc0000000 ---> Stack

Does anybody know, why we leave that much Room unmapped in [1]?

Having at least one page unmapped is ok to catch programmer
errors, but the first 132MB seems a little bit too large...

I still don't know why an allocator ONLY using mmap() and no
brk()/sbrk() shouldn't use mmap(getpagesize(),...).

PS: I used this information already to help someone having these
   kind of problems.

Thanks & Regards

Ingo Oeser
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