It is my understanding that Haiku uses the Hoard memory allocator by Emery Berger. I remember when it was first ported to BeOS. However, it couldn't be updated after the license changed from LGPL to GPL. (unless you pay for a commercial license...) The nedmalloc promises to be competitive but with a very compatible Boost License. http://www.nedprod.com/programs/portable/nedmalloc/index.html Then there is the jemalloc which is under the BSD license. This is what Firefox has chosen for their version 3 and FreeBSD uses it so it should have a lot of eyes on that code for example see http://wordpress.com/tag/jemalloc/ I humbly put this out for your consideration :)