[Help-bash] help on an executable performance

[木先生]

Hi,


    I run a executable file within a bash shell prompt:
    address@hidden:~$ ./executable_file
    Generally, it will run about 5 seconds, and print a line of word such as 
"it take 5s" (clock_gettime is used to measure the running time in the 
executable_file)


    if i redirect the output to a file like tmp.txt:     address@hidden:~$ 
./executable_file > tmp.txt
    it will run about 7 seconds.


    i don't know why the performance drop so dramatically with redirection. 
   Could you help to give some advices?


PS: the platform is:
       kernel:Linux version 3.11.0-15-generic
       Intel(R) Atom(TM) CPU  C2750  @ 2.40GHz




thanks a lot!
George