Re: mmap + mprotect + malloc strange behaviour

[David Addison <addy@quadrics.com>]

Kaloian Manassiev wrote:

>Nevermind, I found it :)
>
>I just found out (by reading
>/usr/src/linux-2.4.20-8/Documentation/sysctl/vm.txt)
>that there is a limit on the number of mappings that a
>process may have and that for some reason malloc
>consumes mappings.
>
>I just increased the limit by editing the file
>/proc/sys/vm/max_map_count. This works okay for my
>application...
>
>Does someone know what repercussions this could have
>on the "normal" operation of the system?
>
>Cheers,
>Kaloian.
>
>
>  
>
The glibc malloc heap switches to using mmap()/munmap() for large 
allocations (>=128kbytes ?). This behaviour can be turned off by setting;

export MALLOC_TRIM_THRESHOLD_=-1
export MALLOC_MMAP_MAX_=0

See also the mallopt() library call.


Cheers
Addy.