Poyarekar: The story of tunables

On his blog, Siddhesh Poyarekar looks at tunables in the GNU C library (glibc). The idea for centralizing the handling of tunable parameters in the library started back 2013, but was added to glibc in version 2.25 that was released in February."Tunables is an internal implementation detail in glibc. It is a way to manage ways in which we allow behaviour in glibc to be modified. As of now the only way to manage glibc is via environment variables and the way to do that was strewn all over the place in the source code. Tunables provide one place to add the tunable parameter with all of the characteristics it would have and then the framework will handle everything from there. The user of that tunable (e.g. malloc for MALLOC_MMAP_THRESHOLD_ or malloc.mmap.threshold in tunables parlance) would then simply access the tunable from the list and do what it wants to do, without bothering about where it came from."