Malloc mmap()
Question Text
When does malloc()
use mmap()
?
Question Answers
When it allocates read-only memory
When it allocates zeroed memory
- When it allocates chunks of memory bigger than an internal threshold
- When the heap is full
Feedback
malloc
uses both brk()
and mmap()
, but prefers mmap()
for big chunks of memory (by default larger than 128 KB).
This value can be altered using mallopt()
with the param
argument set to M_MMAP_THRESHOLD
.
These memroy blocks are unlikely to be reused so they are not placed on heap to avoid memory fragmentation.