Atomic UP test results.




using test-time-probe2.ko

Clock speed : cpu MHz         : 3000.077

Tracing inactive

[  125.787229] test init
[  125.787303] test results : time per probe
[  125.787306] number of loops : 20000
[  125.787309] total time : 204413
[  125.787312] test end
[  175.660402] test init
[  175.660475] test results : time per probe
[  175.660479] number of loops : 20000
[  175.660482] total time : 203468
[  175.660484] test end
[  179.337362] test init
[  179.337436] test results : time per probe
[  179.337440] number of loops : 20000
[  179.337443] total time : 204757
[  179.337446] test end

Res : 10.21 cycles per loop

Atomic UP, one trace, flight recorder.

[  357.983971] test init
[  357.988837] test results : time per probe
[  357.988843] number of loops : 20000
[  357.988846] total time : 12349013
[  357.988849] test end
[  358.718896] test init
[  358.723049] test results : time per probe
[  358.723053] number of loops : 20000
[  358.723057] total time : 12332497
[  358.723059] test end
[  359.422038] test init
[  359.426173] test results : time per probe
[  359.426179] number of loops : 20000
[  359.426182] total time : 12332535
[  359.426185] test end

Res : 616.90 cycles per loop.
205.63 ns per loop

Atomic SMP, one trace, flight.


[  111.694180] test init
[  111.700191] test results : time per probe
[  111.700198] number of loops : 20000
[  111.700201] total time : 16925670
[  111.700204] test end
[  112.285716] test init
[  112.291321] test results : time per probe
[  112.291326] number of loops : 20000
[  112.291329] total time : 16766633
[  112.291332] test end
[  112.880602] test init
[  112.884739] test results : time per probe
[  112.884743] number of loops : 20000
[  112.884746] total time : 12358237
[  112.884748] test end

Res : 767.51 cycles per loop
255.83 ns per loop

(205.63-255.83)/255.83 * 100% = 19.62 %


Difference between
cmpxchg 2967855/20000 = 148.39 cycles or 49.46 ns
cmpxchg-up 540577/20000 = 27.02 cycles or 9.00 ns
irq save/restore 12636562/20000 = 631.82 cycles 210.60 ns






Mathieu Desnoyers, November 2006