For what it's worth, in my tests, Hoard (http://www.hoard.org, https://github.com/emeryberger/Hoard) significantly outperformed SuperMalloc on a machine without TSX. For example, on a simple microbenchmark that tests scalability, Hoard is 2x faster with one thread, and the gap widens with more threads (Hoard is 3.3x faster with 8 threads, 4x faster with 16 threads).