Experimental Physics and
Industrial Control System

Dehong Zhang <[email protected]> · Mon, 11 Aug 2008 15:38:51 -0500

Hi Mark and other friends,

Sorry to cause all the noise.  I think it is working now.

This is one of my own records, it has some floats and some arrays fields.  For the
array which I would like to monitor, I created 2 buffers and let cvt_dbaddr assign one
for user to access while the other is being filled up, then switch.  Then I had another
complication: I also wanted to monitor a float field.  so I was doing:
db_post_event ( for the float)
db_post_event ( for the array whose address toggles between 2 candidates)

Anyway, when I removed the monitoring for the float, and implemented a single
buffer for the array (now I have to memcpy), it seems to be working.  I will try
some combinations to see what exactly was causing all the trouble.

Thank you all very much!  Best regards,
Dehong

----- Original Message -----
From: Mark Rivers <[email protected]>
Date: Monday, August 11, 2008 1:45 pm
Subject: RE: Loosing half the monitor callbacks
To: Dehong Zhang <[email protected]>, Tim Mooney <[email protected]>
Cc: [email protected]

> You need to tell us:
> 
> - What records are you using?  Are these standard EPICS records, or
> records you have written.
> 
> - What device support are you using?  Did you write it?
> 
> I don't believe there is any problem with posting monitors on waveforms
> at >10Hz, I do it frequently and I don't think I am having any problem.
> 
> I suspect there is a problem in your record support or device support.
> 
> Can you send the code where the calls to db_post_events is done?
> 
> Mark
> 
> 
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Dehong Zhang
> Sent: Monday, August 11, 2008 1:34 PM
> To: Tim Mooney
> Cc: [email protected]
> Subject: Re: Loosing half the monitor callbacks
> 
> 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 <[email protected]>
> Date: Saturday, August 9, 2008 11:17 am
> Subject: Re: Loosing half the monitor callbacks
> To: Dehong Zhang <[email protected]>
> Cc: [email protected], [email protected]
> 
> 
> > 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 <[email protected]>
> > > Date: Friday, August 8, 2008 4:43 pm
> > > Subject: RE: Loosing half the monitor callbacks
> > > To: Dehong Zhang <[email protected]>, [email protected]
> > > 
> > > 
> > >> Hi
> > >> Try to set the TPRO field in the IOC to see that it is indeed 
> > >> processing every time
> > >>
> > >> Mohan
> > >>
> > >> ----------------------------------------------------------------
> > >> Mohan Ramanathan  ([email protected])
> > >> 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 <[email protected]>
> > >> Sent: Fri, August 08, 2008 4:30 PM
> > >> To: [email protected]
> > >> 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 ([email protected]) (630)252-5417
> > Beamline Controls & Data Acquisition Group
> > Advanced Photon Source, Argonne National Lab.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System