I do not know how wide spread this problem is, but I have not been able
to install MoscowML due to an unexpected behavior of the malloc version
used by Fedora 7 on my new Intel X86_64 machine. The installation of
MoscowML appears to fail due to the malloc behavior as described below.
I have also found out that mallopt may be a way to control the behavior
of malloc, but it is not very well documented in Fedora.
So I would like to know if mallopt is officially support and if it will
continue to be so. Alternatively, I would like to know if you are able
to suggest any other solution to the problem described below.
Description of problem with installing MoscowML under Fedora 7 on X86_64
machine:
======================================================
I learned earlier this week from Prof. Peter Sestoft (ITU DK) who owns
MoscowML that in my case the problem is caused by certain versions of
malloc(), which during the installation of MoscowML alternatively
allocate memory for the camlrunm (underlying runtime system for
MoscowML) heap in very high addresses using mmap() or in very low
addresses using brk(). This span appears to require a huge page_table
(14 GB or so), which it would be silly to allocate. I also learned from
Peter that the problem can be avoided by either forcing high memory
allocation using this environment variable:
export MALLOC_MMAP_THRESHOLD_=0
or by using forcing low memory allocation using this environment variable:
export MALLOC_MMAP_MAX_=0
However, there may be performance implications of either of these
choices. The latter one would limit usable mosml memory to at most 3 GB,
I think, whereas the former one has been experimentally tested to allow
mosml to use more than 4 GB.
Also note that these environment variables affect *all* programs that
use malloc() and hence may have mysterious side effects.
Thanks
Flemming
