Experimental Physics and Industrial Control System
OK, last week I gave my EPICS Internals talk. It isn't too polished, but I will put it up here for comment. The result is available on the following links:
I feel that it can be used as a start for other similar talks. I spent quite a bit of time on the UML sequence diagrams at the end of the talk and I feel, if they are accurate, that they are also useful for other documentation. I know the ca connection is a bit abbreviated, but I think the others are OK.
In doing this, the main things I was surprised to find was that:
1. The reply from a ca_put_callback goes from the task that calls recGblFwdLink, to cbLow, to CAS-event. The cbLow was a surprise, which allows the event queue to get even more out of order.
2. All ca_monitor responses seem to call dbLock/dbUnlock in the event task. Surely this is only needed for arrays? I feel that this is a lot of unnecessary lock/unlocks.
Anyway, comments welcome.
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From: Andrew Johnson [mailto:firstname.lastname@example.org]
Sent: Tue 04/01/2011 17:45
Cc: Rees, Nick (DLSLtd,RAL,DIA)
Subject: Re: EPICS internals talks?
On Wednesday 29 December 2010 08:11:12 email@example.com wrote:
> I think this is already too much for the time allotted, but I would be
> willing to hear people's comments/suggestions on the way this is going.
Many interesting ideas, although as you say there's a lot more material there
than you have time for. I'm not sure if you know about the detailed record
processing walk-through of a simple 3-record chain in the second half of my
Database Principles talk, see http://www.aps.anl.gov/epics/docs/USPAS2010.php
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will accept it even on the slightest evidence. -- Bertrand Russell
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