Experimental Physics and
Industrial Control System

rivers via Core-talk <core-talk at aps.anl.gov> · Mon, 03 Feb 2020 18:31:08 -0000

I tried Michael's patch.  I does prevent the very fast callbacks
RATE=60, but it slows down the callbacks at all rates.

This is what I now see with RATE=59 when I count for 0.2 seconds.
updateCounts: posting scaler values counts[0]=72
updateCounts: posting scaler values counts[0]=210254
updateCounts: posting scaler values counts[0]=543797
updateCounts: posting scaler values counts[0]=876856
updateCounts: posting scaler values counts[0]=1210206
updateCounts: posting scaler values counts[0]=1543730
updateCounts: posting scaler values counts[0]=1876830
updateCounts: posting scaler values counts[0]=2000000

The average delta of the first 7 readings is (1876830-72)/6.=312793. So
the average callback interval is 31.2 ms, while it should be 1/59 =
16.9 ms.

At RATE=60 I see
updateCounts: posting scaler values counts[0]=73
updateCounts: posting scaler values counts[0]=255761
updateCounts: posting scaler values counts[0]=588997
updateCounts: posting scaler values counts[0]=922397
updateCounts: posting scaler values counts[0]=1255750
updateCounts: posting scaler values counts[0]=1589057
updateCounts: posting scaler values counts[0]=1922543
updateCounts: posting scaler values counts[0]=2000000

So the average callback interval is (1922543-73)/6. = 32.04 ms, while it
should be 16.67 ms.

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https://bugs.launchpad.net/bugs/1861612

Title:
  callbackRequestDelay not waiting for 1/60 sec on vxWorks

Status in EPICS Base:
  New

Bug description:
  The problem is documented in this tech-talk thread:
  https://epics.anl.gov/tech-talk/2020/msg00308.php

  In 7.0.3.1, but not in 7.0.3, callbackRequestDelay(1/60) results in
  100% CPU time, most of the time in cbHigh.

  This happens on vxWorks 6.9.4.1 and was first seen with the scaler
  record with multiple types of scaler hardware and device support.

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System