I want to know what open source projects are used things like arena, allocators, overloading new and etc. This refers to the C + + language.
See google perf tools and jemalloc. The last one is used in freebsd as default malloc implementation. So, every project that use any of this two use arenas, cause both use them internally. new operator in c++ is usually implemented with libc's malloc function. Also, see nginx http server sources, it allocates memory pool for the session before the connection is created (but it's written in pure c). Apache has an apr pools library.