What the meaning of 'CPU latency' in p2pBandwidthLatencyTest ?

Following is a snippet of my result with p2pBandwidthLatencyTest

  1 P2P=Disabled Latency Matrix (us)
  2    GPU     0      1      2      3
  3      0   2.61  14.95  19.61  14.42
  4      1  11.09   2.10  19.16  18.72
  5      2  13.34  16.44   2.06  16.80
  6      3  11.92  16.62  16.72   2.09
  7
  8    CPU     0      1      2      3
  9      0   2.67   6.78   6.18   6.14
 10      1   6.71   2.62   6.33   6.30
 11      2   6.35   6.27   2.50   5.78
 12      3   6.20   6.24   5.79   2.49
 13 P2P=Enabled Latency (P2P Writes) Matrix (us)
 14    GPU     0      1      2      3
 15      0   2.59   2.31   1.85   1.86
 16      1   2.26   2.10   1.88   1.83
 17      2   1.81   1.83   2.07   2.31
 18      3   1.84   1.81   2.23   2.09
 19
 20    CPU     0      1      2      3
 21      0   2.71   1.91   1.97   1.93
 22      1   2.11   2.77   2.16   2.00
 23      2   1.92   1.76   2.58   1.94
 24      3   1.84   1.91   1.88   2.55

When I enabled P2P, GPU latency decreases because they use NVLink (line 2 ~ 6, 14 ~ 18).
By the way, what does CPU latency represent for? I don't know why they show it and sometime I don't understand the result. For instance, line number 23, CPU latency (1.92) is bigger than GPU latency(1.81) even if GPU clock encloses CPU clock https://github.com/NVIDIA/cuda-samples/blob/master/Samples/5_Domain_Specific/p2pBandwidthLatencyTest/p2pBandwidthLatencyTest.cu#L527C1-L528C1. which means GPU clock is always behind CPU clock.

My hardware spec is A100 80GB x 4 with NVLink Bridge (GPU 0-1, 2-3 connected)

Start with p2pBandwidthLatencyTest.cu at the linked lines 527-528 and read the surrounding latency measurement code. Compare the CPU and GPU sections in the reported output. Done means documenting what CPU latency represents and how it relates to the GPU latency values, including the A100 example.