jemalloc started out as the memory allocator for a programming language runtime in 2005, but language design changes made the allocator superfluous. At the time, FreeBSD was in need of an SMP-scalable allocator, so I integrated jemalloc into FreeBSD’s libc, and then made a long series of improvements to scalability and fragmentation behavior.
In late 2007, the Mozilla Project was hard at work improving Firefox’s memory usage for the 3.0 release, and jemalloc was used to solve fragmentation problems for Firefox on Microsoft Windows platforms. You can read here about the fruits of that labor. I made many enhancements to jemalloc while developing for Mozilla, and all of the generic algorithmic improvements were incorporated into FreeBSD’s jemalloc. More recently, Mozilla sponsored integration of Apple Mac OS X support into the stand-alone jemalloc.
Since 2009 I have adapted jemalloc to handle the extreme loads Facebook servers commonly operate under. Facebook uses jemalloc in many components that are integral to serving its website. Facebook supports numerous open source projects, and is to thank for sponsoring many of the features that first appeared in the stand-alone jemalloc.