RE: Waveform record I/O interrupt. asyn

["Hill, Jeff" <johill@lanl.gov>]

 

This is the upgrade to EPICS for parasitic tagging, and subscription update filtering, I have  described in previous talks. Most of our LANSCE LINAC beam species “flavored” data is also array data so a solid implementation is a crucial requirement here at LANSCE. Our requirements also include a fix, actually a substantial improvement, for the event queue subscription-A-to-subscription-B ordering issue.

 

Jeff

 

From: Williams Jr., Ernest L. [mailto:ernesto@slac.stanford.edu]
Sent: Friday, February 21, 2014 7:00 PM
To: Hill, Jeff
Cc: Dalesio, Leo; Vishnu Patel; techtalk
Subject: Re: Waveform record I/O interrupt. asyn

 

Sent from my iPhone

On Feb 21, 2014, at 5:26 PM, "Hill, Jeff" <johill@lanl.gov> wrote:

Ø  the event queue does not buffer arrays – it only queues up the pointer to the

Ø  array. If you are reusing the same buffer (as the waveform record does) it may

Ø  also be overwritten if the client is not taking the data fast enough.

 

Ø  We are working on ways to better support very large arrays in EPICS V4 – these

Ø  must be done for us over the next 12 months – but only pieces are done now.

 

We are deploying a fix for this issue at LANSCE which is, in contrast, implemented into V3.

 

Can you give some details on this fix?

 

Jeff

 

From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Dalesio, Leo
Sent: Friday, February 21, 2014 3:52 PM
To: Vishnu Patel; techtalk
Subject: RE: Waveform record I/O interrupt. asyn

 

Yes – this is true. Some options:

There are some options

You could write something in the driver that allocates memory on initialization and puts the arrays in there – point the device support at the buffered data.

Disable the digitizer until it is rearmed

Look are areaDetector for processing the arrays under the EPICS database

 

Channel Access also does not buffer arrays – it only queues up the pointer to the array. If you are reusing the same buffer (as the waveform record does) it may also be overwritten if the client is not taking the data fast enough.

 

We are working on ways to better support very large arrays in EPICS V4 – these must be done for us over the next 12 months – but only pieces are done now.

 

Bob

 

From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Vishnu Patel
Sent: Friday, February 21, 2014 12:35 PM
To: techtalk
Subject: Waveform record I/O interrupt. asyn

 

Hello,

     I am facing problem in I/O Interrupt for waveform record in the asyn.  If the value of waveform record change very fast then some of the samples missing or same sample repeat twice even if  before p_interruptInt32Array->callback () function the value is scanned properly by driver. But i think the read value is pushed to the callback but it is not handle that much fast in the callback.

 

 

I checked the code for interruptCallbackInput   in devAsynXXXArray.h. 

In devAsynXXXArray.c  dbScanUnlock has been used before  scanIoRequest().   Can it create problem for repeating same value?  

My assumption is as dbScanUnlock  and before scanIoRequest() execute, value change and second time triggers interrupt. This result same value for both interrupts.

 

I checked interrupt callback code  in devAsynInt32.c where  epicsMutexUnlock has been used after scanIoRequest(). 

 

 

Thank you

 

Vishnu

 

     

 

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