Clock test: which C clock is the fastest?

In one of my application it gets timer a lot of times, so I must make sure which timer is faster.

I tested three common timer functions:
gettimeofday() (in windows we use GetLocalTime())
clock() (in windows we use GetTickCount())
time()

I tested them under unix/linux, each function called 1e6(1M or 1000k) times.

Result on my unix computer:

test_gettimeofday()  42.40ms
test_clock()        344.27ms
test_time()         183.65ms

Result on my Linux VPS:

test_gettimeofday() 190.00ms
test_clock()        320.00ms
test_time()         160.00ms

Result on my VoCore v0.3 (RT5350F MIPS 360MHz) board: ( it is slow 😀 )

test_gettimeofday() 1370.00ms
test_clock()        1800.00ms
test_time()         520.00ms

On my board, time() win, that is out of my expectation. OpenWrt are using uLibC but not glibC whose time() is calling gettimeofday(). uLibC must be using some other way.

But for average result, looks like gettimeofday() is the winner :)

source code download link: http://vonger.cn/upload/clock.c