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<== Date ==> <== Thread ==>

Subject: string and array buffering in soft IOCs
From: Kurt Biery <biery@fnal.gov>
To: johill@lanl.gov
Cc: core-talk@aps.anl.gov
Date: Wed, 10 Jan 2007 08:22:49 -0600
Hi Jeff,
This note is a follow-up to my earlier posting on tech-talk regarding the buffering of string and array record data. (Thanks for your reply!)

As I mentioned in my tech-talk message, we would like to use process variables in soft IOCs to pass string messages between processes in a DAQ system that we're designing. I should have been more careful in that email, though, to mention that we're not suggesting that lots of large messages get buffered for long periods of time. Rather, I was asking how one might configure EPICS to gracefully handle (reasonably short) bursts of messages in a system in which the average rate of message production can easily be handled by the subscribers. For example, the scenario that I presented in my tech-talk message which had a waveform record of 32 bytes being quickly updated 100 times and then left alone for a long time seemed like a scenario in which we might reasonably expect the 100 messages to be reliably delivered. From the tech-talk responses that I received, though, it sounds like the graceful handling of bursts would be an enhancement rather than something that we can configure. I described all of this to the NOvA DAQ group yesterday afternoon, and folks were supportive of learning more about the code changes that would be needed. After the meeting, Margaret Votava and a few others in our group phoned Andrew Johnson to get his input on how we might most constructively make such changes. Andrew mentioned that you've had plans for some time for an upgrade that would allow users to specify some amount of string or array buffering, and he suggested that we ask you about that (and cc: core-talk). It's possible that our group could contribute to that development, and we would like to understand the scope. Do you have time to talk about this at some point?
Thanks,
Kurt


Replies:
RE: string and array buffering in soft IOCs Jeff Hill

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