[dpdk-dev] [Bug 385] latency calculation has potential performance issues

[bugzilla at dpdk.org]

https://bugs.dpdk.org/show_bug.cgi?id=385

            Bug ID: 385
           Summary: latency calculation has potential performance issues
           Product: DPDK
           Version: 19.11
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: minor
          Priority: Normal
         Component: other
          Assignee: dev at dpdk.org
          Reporter: stephen at networkplumber.org
  Target Milestone: ---

If anyone is using rte_latencystats, they are in for a big performance hit.

The code in rte_latencystats uses a receive and transmit callback for each
burst. The latency calculation is using floating point (slow) and worse yet
there is several floating point divides per packet. A floating point divide is
one of the slowest opcodes on any processor.

The code should be changed to keep track of cycles (fixed point 64 bit) and
convert the result to floating point when doing update. Or better yet only
use fixed point maths.

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