Recently, I was asked to constrain the memory usage of an application on Linux. Glibc provides hooks for [malloc, free, etc](http://www.gnu.org/software/libc/manual/html_node/Hooks-for-Malloc.html). By the way, the hook functions are responsible to guarantee thread safety — glibc doesn’t do it automatically. I used the malloc hooks in combination with a memory manager that a colleague found: TLSF. There are two implementations:
* [http://tlsf.baisoku.org/](http://tlsf.baisoku.org/) (public domain)
* [http://rtportal.upv.es/rtmalloc/](http://rtportal.upv.es/rtmalloc/) (GPL)
There are benefits and caveats when using a custom memory allocator. TLSF was meant to shine for real-time use, because the overhead of malloc and free are O(1) constant-time operations. On the other hand, TLSF isn’t thread-safe.