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malloc() and brk()

Question Text​

When does malloc() use brk()?

Question Answers​

  • brk() is outdated, malloc() always uses mmap()
  • When it allocates a small chunk of memory

  • When it allocates an array

  • When it's working with dynamic libraries

Feedback​

malloc() uses both brk() and mmap(), but prefers brk() for small chunks of memory to keep granular allocations in a contiguous area. This way, free() does not necessarily return the memory to the OS as it might only mark the zone as "free" within libc's allocator and reuse it for later allocations.