Experimental Physics and
Industrial Control System

Mark Rivers via Core-talk <[email protected]> · Sun, 7 Apr 2019 22:38:31 +0000

> Also, SCANTIME doesn't seem to change if I remove 99% if the devices/records.

How about the warnings from the scan the 1 second scan thread.  Have you tested how many records or what specific records you need to remove to eliminate those warnings?

Mark

________________________________
From: [email protected] <[email protected]> on behalf of Konrad, Martin via Core-talk <[email protected]>
Sent: Sunday, April 7, 2019 3:43 PM
To: Michael Davidsaver; EPICS Core Talk
Subject: Re: Excessive scan times for periodic scans

Hi Michael,
I like your idea of measuring the scan time using a pair of records with
higher/lower PHAS field. I added the following records (all other
records on my IOC have PHAS=0):

record(ai, "PHAS-1") {
  field(DTYP, "Soft Timestamp")
  field(SCAN, "1 second")
  field(PHAS, "-1")
}

record(ai, "PHAS1") {
  field(DTYP, "Soft Timestamp")
  field(SCAN, "1 second")
  field(PHAS, "1")
  field(FLNK, "SCANTIME")
}

record(calc, "SCANTIME") {
  field(INPA, "PHAS-1 NPP MS")
  field(INPB, "PHAS1 NPP MS")
  field(CALC, "1e6*(B-A)")
  field(EGU,  "us")
}

The result is interesting: SCANTIME reads somewhere between 10 and 100
µs. At the same time I'm getting warnings from the '1 second' scan
thread ("Scan processing averages 1.440 seconds (1.020 .. 2.110)"). Any
idea why the SCANTIME PV and the times in the warning don't line up?
Also, SCANTIME doesn't seem to change if I remove 99% if the
devices/records.

If I monitor a few arbitrary PVs with PHAS 0 I can see them update a
while (for example ~60 ms or ~200 ms) after PHAS1 processes. This
confirms that my records finish processing asynchronously.

Is the scan thread measuring the time until the last asynchronous PV has
received its callback?

Thanks a lot,

Martin

--
Martin Konrad
Facility for Rare Isotope Beams
Michigan State University
640 South Shaw Lane
East Lansing, MI 48824-1321, USA
Tel. 517-908-7253
Email: [email protected]

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System