Re: Loosing half the monitor callbacks

[Dehong Zhang <dhzhang@fnal.gov>]

Hi Tim (and Jeff),

There seems to be a little imperfection somewhere.

In my record, I try to "monitor" 2 fields: a float and an array of floats
(288 elements).  What I want is to get updates at about 5Hz.  It does
not work -- missing every the other update but get those lucky ones
twice -- still getting 5 Hz but half the information.

I tried to slow down the system to about one update every 3 seconds.
It still behaves the same way.  However when I commented out the
db_post_event for the array, the monitoring for the single float works
correctly.  The problem seems to be related to the array.

In the Tech-Talk DB, Jeff once replied to someone about buffering
in Epics (the guy had very similiar problem).  Am I hit by the same thing?
It is hard to imagine that at 0.3 Hz I would run into buffer-full or out-
of-memory problems.  I would imagine that at a slow enough rate,
it should work with whatever buffering or flowControl.

Is there a way to re-config the IOC so that it can 'monitor' small arrays
at <= 10 Hz?  My processor has 500 MB memory.

Thank you very much.  Best regards,
Dehong




----- Original Message -----
From: Tim Mooney <mooney@aps.anl.gov>
Date: Saturday, August 9, 2008 11:17 am
Subject: Re: Loosing half the monitor callbacks
To: Dehong Zhang <dhzhang@fnal.gov>
Cc: mohan@aps.anl.gov, tech-talk@aps.anl.gov


> Dehong,
> I think this shows that the problem is not in channel access, but in the
> database or lower.  You're not losing monitor callbacks, the record is
> posting the same value twice, with the same time stamp.  You can get
> another clue to what this means by looking at the record-support code,
> and finding calls to recGblGetTimeStamp() and calls to db_post_events()
> for the CTME field.
> 
> Dehong Zhang wrote:
> > Hi Friends Kay, Mark and Mohan,
> > 
> > Thank you very much for the advices.
> > 
> > I just tried camonitor.  It is doing the same thing: throw away 
> every the other
> > change, but callback two times for the other ones.  The printout is 
> like:
> > 
> > fastTimeTest.CTME              2008-08-08 16:46:02.609123 
> 6.88202e+06 
> > fastTimeTest.CTME              2008-08-08 16:46:02.859123 
> 7.38478e+06 
> > fastTimeTest.CTME              2008-08-08 16:46:02.859123 
> 7.38478e+06 
> > fastTimeTest.CTME              2008-08-08 16:46:03.259123 
> 8.01506e+06 
> > fastTimeTest.CTME              2008-08-08 16:46:03.259123 
> 8.01506e+06 
> > fastTimeTest.CTME              2008-08-08 16:46:03.659123 137329 
> > fastTimeTest.CTME              2008-08-08 16:46:03.659123 137329 
> > fastTimeTest.CTME              2008-08-08 16:46:04.059123 817524 
> > fastTimeTest.CTME              2008-08-08 16:46:04.059123 817524 
> > 
> > Does the record update time stamps tell anything?  Am I running too 
> fast?
> > 
> > Thank you again.  Best regards,
> > Dehong
> > 
> > 
> > 
> > 
> > 
> > ----- Original Message -----
> > From: Mohan Ramanathan <mohan@aps.anl.gov>
> > Date: Friday, August 8, 2008 4:43 pm
> > Subject: RE: Loosing half the monitor callbacks
> > To: Dehong Zhang <dhzhang@fnal.gov>, tech-talk@aps.anl.gov
> > 
> > 
> >> Hi
> >> Try to set the TPRO field in the IOC to see that it is indeed 
> >> processing every time
> >>
> >> Mohan
> >>
> >> ----------------------------------------------------------------
> >> Mohan Ramanathan  (mohan@aps.anl.gov)
> >> Senior Beamline Engineer, Advanced Photon Source
> >> Argonne National Laboratory, Argonne, IL 60439
> >> (630)-252-3773/ (630)-822-5625(Cell)
> >> ----------------------------------------------------------------
> >>
> >> [Message delivered by NotifyLink]
> >>
> >> ----------Original Message----------
> >>
> >> From: Dehong Zhang <dhzhang@fnal.gov>
> >> Sent: Fri, August 08, 2008 4:30 PM
> >> To: tech-talk@aps.anl.gov
> >> Subject: Loosing half the monitor callbacks
> >>
> >>
> >> Hi,
> >>
> >> I would like to monitor a PV at 5 Hz.  Somehow I do get 5 callbacks 
> 
> >> every seconds
> >> but only get the changes every the other time, like getting changes 
> 
> >> 1st, 3rd, 5th ...
> >> two times, but never get changes 2nd, 4th, ...
> >>
> >> Could you please enlighten me?
> >>
> >> Thanks and best regards,
> >> Dehong
> >>
> 
> -- 
> Tim Mooney (mooney@aps.anl.gov) (630)252-5417
> Beamline Controls & Data Acquisition Group
> Advanced Photon Source, Argonne National Lab.