[SOLVED] Why does Firefox have an empty heap on Linux? Where does malloc go in memory?

Issue

The start_brk and brk feild of mm_struct have same value for Firefox, which means the heap is empty in Firefox. Does anyone know: Why does Firefox have an empty heap on Linux? Where does malloc go in memory?

Solution

Firefox uses a custom memory allocator, jemalloc. Unless the --enable-dss option is specified during configuration, this allocator uses only mmap(), otherwise it uses both sbrk() and mmap(). Needless to say, only the brk() system call will modify the start_brk and brk fields of the struct in question.

Answered By - Michael Foukarakis