Re: Prioritizing Channel Access per Record?

[Brian Bevins <bevins@jlab.org>]

Hi Mark,

The waveforms are soft records that have their buffers filled by 
dedicated threads, which then post events to process the records.

I only see the slowdown when a client is connected to the waveforms. 
Even with the waveform records processing normally, the "fast" records 
update normally as long as no CA clients monitor the waveforms. I 
interpreted this to mean that the CA traffic was the bottleneck, but 
maybe I'm wrong.

Thanks,
--Brian

On 03/18/14 12:23, Mark Rivers wrote:
> Are you certain that it is the CA update of the waveform records that is slowing it down, and not the record processing?  if your waveform records are using synchronous device support and they take a long time to process that can slow down all other records.  What type of device support do your waveform records have, synchronous or asynchronous?
>
> Mark
>
>
> -----Original Message-----
> From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Brian Bevins
> Sent: Tuesday, March 18, 2014 10:47 AM
> To: EPICS Techtalk
> Subject: Prioritizing Channel Access per Record?
>
> Is there any way to specify that CA delivery of updates from certain
> records should be prioritized over other records on the same ioc?
>
> I've got an application where a bunch of ai's are processed at 10Hz and
> some relatively big (for us) waveforms are processed at about 0.3-0.5
> Hz. The ioc is not heavily loaded and all record processing seems to
> happen in a timely way, but from the client end (EDM) the "fast" records
> all pause for ~0.5 sec whenever the waveforms push out their CA updates.
>
> The ai's are already being processed at a higher priority, but this
> doesn't seem to help their updates get pushed out with higher priority.
>
> Is there some tinkering I can do with the priorities of the CA threads
> to get what I want? How can I tell which thread will get which record
> updates? Is there something more obvious I'm missing?
>
> Thanks,
> --Brian


--
Brian S. Bevins, PE
Computer Scientist / Mechanical Engineer
Thomas Jefferson National Accelerator Facility

     "The urge to save humanity is almost always only a false-face
      for the urge to rule it."
                                     -- H. L. Mencken