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Where exactly is overflow (OVF) detected?

Hi, I am often getting overflow (OVF) packets from Intel PT on a small Goldmont Plus processor, and I'm wondering exactly what is overflowing. Is it some kind of on-chip buffer, or is it the RAM allocation that was configured by the operating system to receive the PT packets? It would be great to have a diagram that gives a precise overview of the dataflow stages for tracing on Linux via perf_event_open(). Here's my setup:

  • Mini PC
    • CPU model Gemini Lake
    • 8GB RAM
  • Fedora 29
  • decoding via Intel libipt (pt_packet_decoder only)

I also get overflows on my Xeon and i7 machines when running larger benchmarks, such as the SPEC 2017 reference data sets. Is there anything I can do to improve the reliability of the tracing, or is it simply subject to overflow on occasion? Thanks for your help.

Byron

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