用 RDTSC，CPUID 和 RDTSCP 測量效能的範例

說明

• 根據 How to Benchmark Code Execution Times on Intel® IA-32 and IA-64 Instruction Set Architectures 這篇文章

下載

• http://adf.ly/1BpCYo

結果

• Loading hello module...
  loop_size:0 >>>> variance(cycles): 2; max_deviation: 4 ;min time: 44
  loop_size:1 >>>> variance(cycles): 27; max_deviation: 1556 ;min time: 44
  loop_size:2 >>>> variance(cycles): 234861; max_deviation: 153248 ;min time: 44
  .........
  .........
  loop_size:997 >>>> variance(cycles): 22; max_deviation: 1412 ;min time: 44
  loop_size:998 >>>> variance(cycles): 40; max_deviation: 1388 ;min time: 44
  loop_size:999 >>>> variance(cycles): 3; max_deviation: 4 ;min time: 44
  
  total number of spurious min values = 0
  total variance = 34752
  absolute max deviation = 1477968
  variance of variances = 495049069215
  variance of minimum values = 0
  

心得

• 看起來還過得去，至少最小結果都相同。變異數雖然很大，代表每次的測量誤差很高，不過 100000 次的測量能得到這結果也還可以啦。順帶一提，原文的測量結果變異數僅有 2，代表每次的測量誤差僅有 1.4 個 cycle，非常準確

資源

• How to Benchmark Code Execution Times on Intel® IA-32 and IA-64 Instruction Set Architectures