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pcm-pcie numbers are way off

While trying to understand the DDIO misses to hit ratio, I stumbled upon the pcm-pcie.x tool.

I ran it with the as pcm-pcie.x -e -B 30 to get the extended output with DDIO, in bytes, once 30s.

There are two Xeon Gold 6126 CPU @ 2.60GHz CPUs and two X710 cards (each on a separate NUMA node).

This is a packet sniffer, AKA this host does not transfer anything into the network, it just captures packets. There's also little traffic - 1-2Gbit/sec on average.

  1. The DDIO miss / hit ratio look awful
  2. The PCIe RD / Wr counters seem to be off
  3. Why do counters report so much of data being read by the card from the host, when it's not transmiting anything at all? In fact, they say cards read more than they write. There's nothing else that could write that much - almost nothing written to disk, etc.
Skt | PCIeRdCur |  RFO  |  CRd  |  DRd  |  ItoM  |  PRd  |  WiL  | PCIe Rd (B) | PCIe Wr (B)
 0      50 M        28 M    26 M    26 M     16 M    21 M    16 M        8459 M        2843 M	(Total)
 0      33 M        31 M    28 M    21 M     14 M    20 M    21 M        7403 M        2989 M	(Miss)
 0      16 M         0       0    5181 K   1486 K   826 K     0          1415 M          95 M	(Hit)
 1      35 M        32 M    39 M    37 M     28 M    30 M    20 M        9329 M        3890 M	(Total)
 1      35 M        43 M    37 M    32 M     25 M    24 M    22 M        9587 M        4429 M	(Miss)
 1     175 K         0    1940 K  4919 K   2652 K  6050 K     0           450 M         169 M	(Hit)

 

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