New libc malloc patch

There is a patch that contains a new libc malloc implementation at:

http://www.canonware.com/~jasone/jemalloc/jemalloc_20051127a.diff

This implementation is very different from the current libc malloc.   
Probably the most important difference is that this one is designed  
with threads and SMP in mind.

The patch has been tested for stability quite a bit already, thanks  
mainly to Kris Kennaway.  However, any help with performance testing  
would be greatly appreciated.  Specifically, I'd like to know how  
well this malloc holds up to threaded workloads on SMP systems.  If  
you have an application that relies on threads, please let me know  
how performance is affected.

Naturally, if you notice horrible performance or ridiculous resident  
memory usage, that's a bad thing and I'd like to hear about it.

Thanks,
Jason

=== Important notes:

* You need to do a full buildworld/installworld in order for the  
patch to work correctly, due to various integration issues with the  
threads libraries and rtld.

* The virtual memory size of processes, as reported in the SIZE field  
by top, will appear astronomical for almost all processes (32+ MB).   
This is expected; it is merely an artifact of using large mmap()ed  
regions rather than sbrk().

* In keeping with the default option settings for CURRENT, the A and  
J flags are enabled by default.  When conducting performance tests,  
specify MALLOC_OPTIONS="aj" .