lockfree-malloc is a scalable drop-in replacement for malloc/free.

* It's thread-friendly. It supports a practically-unlimited number of
  concurrent threads, without locking or performance degradation.
* It's efficient, especially in a multi-threaded environment. Compared to
  a stock libc allocator, we see a significant performance boost.
* It does NOT fragment or leak memory, unlike a stock libc allocator.
* It wastes less memory. For small objects (less than 8kb in size), the
  overhead is around 0 bytes. (!)
* It is designed from the ground-up for 64-bit architectures.
* It is elegant. The whole codebase is only around 800 lines of fairly
  clean C++. (!)
* It fully stand-alone; it does not rely on pthreads or libc at runtime.

WWW: https://github.com/Begun/lockfree-malloc