Re: Prioritizing Channel Access per Record?

[Ralph Lange <Ralph.Lange@gmx.de>]

On 18.03.2014 17:30, Brian Bevins wrote:
> 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.

Hmmm... another idea:

Please check that you have no database links that would pull "fast" and 
"slow" records into the same lock set.

During record processing, waveforms are put in the CA send queue by 
reference, while atomic data is put directly into the queue.
When the low-priority CA send thread later-on copies the data out of the 
record into the network buffer, it has to lock the record. (It can just 
copy from the queue for atomic data, which does not require locking.)
Possible effect: if your database has link connections that pull 
waveform records and "fast" records into the same lock set, the "fast" 
records might block while CA copies data from the waveforms.

Perfectly harmless looking things, like SDIS links pointing to the same 
"disable" record, may easily pull far too many records into the same 
lock set.
Making this kind of links ".CA" often helps by breaking up the lock sets 
without affecting function.

~Ralph


> 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