Emacs does this on startup:
mmap(NULL, 154618822656, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0) = -1 ENOMEM (Cannot allocate memory)
MAP_NORESERVE does not have the intended effect with vm.overcommit_memory=2 (which enables the beancounter/disables overcommit).
The standard way of reserving address space is to use a PROT_NONE mapping and make parts readable/writable as needed using mprotect later. This will work with vm.overcommit_memory=2 as well because initially PROT_NONE mappings do not count towards the commit limit.
Is Emacs doing this? Or is it actually webkit, as in bug 1569478?
*** This bug has been marked as a duplicate of bug 1569478 ***