"Traditionally, allocators have used sbrk(2) to obtain memory, which is suboptimal for several reasons, including race conditions, increased fragmentation, and artificial limitations on maximum usable memory. If sbrk(2) is supported by the operating system, this allocator uses both mmap(2) and sbrk(2), in that order of preference; otherwise only mmap(2) is used."
Also, Google's tcmalloc uses mmap to get system memory:
"An allocation for k pages is satisfied by looking in the kth free list. If that free list is empty, we look in the next free list, and so forth. Eventually, we look in the last free list if necessary. If that fails, we fetch memory from the system mmap."
In fact I'd be surprised to see a modern malloc implementation that doesn't use mmap under the hood.
http://jemalloc.net/jemalloc.3.html
"Traditionally, allocators have used sbrk(2) to obtain memory, which is suboptimal for several reasons, including race conditions, increased fragmentation, and artificial limitations on maximum usable memory. If sbrk(2) is supported by the operating system, this allocator uses both mmap(2) and sbrk(2), in that order of preference; otherwise only mmap(2) is used."
Also, Google's tcmalloc uses mmap to get system memory:
https://github.com/google/tcmalloc/blob/master/docs/design.m...
"An allocation for k pages is satisfied by looking in the kth free list. If that free list is empty, we look in the next free list, and so forth. Eventually, we look in the last free list if necessary. If that fails, we fetch memory from the system mmap."
In fact I'd be surprised to see a modern malloc implementation that doesn't use mmap under the hood.