perf trace有类似于strace功能，可以实时监控程序的系统调用：
# perf trace ./a.out
0.032 ( 0.002 ms): a.out/7673 brk( ) = 0x1e6b000
0.051 ( 0.005 ms): a.out/7673 access(filename: 0xb7c1cb00, mode: R ) = -1 ENOENT No such file or directory
0.063 ( 0.005 ms): a.out/7673 open(filename: 0xb7c1a7b7, flags: CLOEXEC ) = 3
0.070 ( 0.002 ms): a.out/7673 fstat(fd: 3, statbuf: 0x7ffffb72bc80 ) = 0
0.073 ( 0.004 ms): a.out/7673 mmap(len: 38436, prot: READ, flags: PRIVATE, fd: 3 ) = 0x7f18b7e15000
0.079 ( 0.001 ms): a.out/7673 close(fd: 3 ) = 0
0.087 ( 0.005 ms): a.out/7673 open(filename: 0xb7e21ec0, flags: CLOEXEC ) = 3
0.093 ( 0.003 ms): a.out/7673 read(fd: 3, buf: 0x7ffffb72be28, count: 832 ) = 832
0.099 ( 0.002 ms): a.out/7673 fstat(fd: 3, statbuf: 0x7ffffb72bcc0 ) = 0
0.102 ( 0.003 ms): a.out/7673 mmap(len: 8192, prot: READ|WRITE, flags: PRIVATE|ANONYMOUS, fd: -1 ) = 0x7f18b7e13000
0.110 ( 0.004 ms): a.out/7673 mmap(len: 2283024, prot: EXEC|READ, flags: PRIVATE|DENYWRITE, fd: 3 ) = 0x7f18b79cf000
0.116 ( 0.007 ms): a.out/7673 mprotect(start: 0x7f18b79fc000, len: 2093056 ) = 0
0.125 ( 0.005 ms): a.out/7673 mmap(addr: 0x7f18b7bfb000, len: 8192, prot: READ|WRITE, flags: PRIVATE|DENYWRITE|FIXED, fd: 3, off: 180224) = 0x7f18b7bfb000
0.142 ( 0.002 ms): a.out/7673 close(fd: 3 ) = 0
0.153 ( 0.006 ms): a.out/7673 open(filename: 0xb7e134c0, flags: CLOEXEC ) = 3
0.161 ( 0.003 ms): a.out/7673 read(fd: 3, buf: 0x7ffffb72bdf8, count: 832 ) = 832
0.165 ( 0.002 ms): a.out/7673 fstat(fd: 3, statbuf: 0x7ffffb72bc90 ) = 0
0.169 ( 0.005 ms): a.out/7673 mmap(len: 2216432, prot: EXEC|READ, flags: PRIVATE|DENYWRITE, fd: 3 ) = 0x7f18b77b1000
......