Re: memory allocation problems

[Andi Kleen]

On Fri, Apr 06, 2001 at 10:06:47AM -0400, [e-mail] wrote:
>   Essentially, the problem can be summarized to be that on a machine
>   with ample ram (2G, 4G, etc), I am unable to malloc a gig if I ask 
>   for the memory in small ( <= 128k) chunks. I've enclosed some results 
>   and a little program which was put together to demonstrate the problems
>   we're having.  All of the failures seem to occur around 930MB.

It's bumping against some mapping (just do system("cat /proc/self/maps")
on allocation failure to see which). Usual suspects are shared libraries.
One possible solution is to upgrade to a newer glibc, the 2.2 glibc malloc 
should handle this case better.  
A way to get mappings like shared libraries out of the way is to 
increase the value of TASK_UNMAPPED_BASE in include/asm-i386/processor.h.
For that the kernel needs to be recompiled and it should be smaller
TASK_SIZE-enough space for your shared libraries. With that even the older
malloc will probably work.

-Andi