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tx timestamping failed

Sometimes, users will see the following in their kernel logs:

[Sep24 20:53] exanic 0000:1a:00.0 enp26s0: tx timestamping failed

[Sep24 22:05] exanic 0000:1a:00.0 enp26s0: tx timestamping failed

[Sep24 23:55] exanic 0000:1a:00.0 enp26s0: tx timestamping failed



The ExaNIC takes a hardware timestamp of each received packet, and this is passed up to the host as metadata for that packet.


Transmit timestamps are handled differently.  The card will take a timestamp of each transmitted packet (per interface), and save this to a register that the host can read.  If there is a large amount of traffic being sent out a given interface, the host can lose track of the which packet a given transmit timestamp applies to.  Depending on the frequency of these events, this can have an adverse impact on time synchronization daemons that rely on transmit timestamps, for example PTP.

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  1. Phil Manuel

  2. Posted
  3. Updated

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