$ strace -e mmap2,munmap perl -e '{"x" x 1048576}{"x" x 1048576}{"x" x 1048576}' 2>&1 |tail -6
mmap2(NULL, 1052672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb740c000
mmap2(NULL, 1052672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb730b000
mmap2(NULL, 1052672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb720a000
munmap(0xb720a000, 1052672)             = 0
munmap(0xb730b000, 1052672)             = 0
munmap(0xb740c000, 1052672)             = 0