[dpdk-dev] [Bug 450] wrong report for cycles/pkt or pps

[dpdk-dev] [Bug 450] wrong report for cycles/pkt or pps

[bugzilla]

https://bugs.dpdk.org/show_bug.cgi?id=450

            Bug ID: 450
           Summary: wrong report for cycles/pkt or pps
           Product: DPDK
           Version: 20.02
          Hardware: ARM
                OS: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: testpmd
          Assignee: dev@dpdk.org
          Reporter: ogerlitz@mellanox.com
  Target Milestone: ---

According to doc/guides/prog_guide/profile_app.rst RTE_ARM_EAL_RDTSC_USE_PMU
has to be used over ARM CPU to get correct cyc/pkt report. This involves using
OOT (non upstream) kernel module which is problematic and reported to be
non-stable. 

Moreover, once the PMU configuration is set, the pps report done by testpmd is
wrong, so this doesn't really help, as one wants to see both pps and cyc/pkt.

If the PMU configuration is not set, indeed the cyc/pkt report is wrong, but
this is due to using a timer which is not running in the CPU frequency. If the
CPU frequency would be used we can get a correct cyc/pkt report without the PMU
config.

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