Argonne National Laboratory

Experimental Physics and
Industrial Control System

2002  2003  2004  2005  2006  2007  2008  2009  2010  <20112012  2013  2014  2015  2016  2017  2018  2019  Index 2002  2003  2004  2005  2006  2007  2008  2009  2010  <20112012  2013  2014  2015  2016  2017  2018  2019 
<== Date ==> <== Thread ==>

Subject: RE: EPICS internals talks?
From: <nick.rees@diamond.ac.uk>
To: <anj@aps.anl.gov>, <core-talk@aps.anl.gov>
Date: Fri, 21 Jan 2011 22:44:02 +0000
Hi All,

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:

http://controls.diamond.ac.uk/downloads/other/files/EpicsInternals.ppt
http://controls.diamond.ac.uk/downloads/other/files/EpicsInternals.pdf

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.

Cheers

Nick Rees
Principal Software Engineer           Phone: +44 (0)1235-778430
Diamond Light Source                  Fax:   +44 (0)1235-446713



-----Original Message-----
From: Andrew Johnson [mailto:anj@aps.anl.gov]
Sent: Tue 04/01/2011 17:45
To: core-talk@aps.anl.gov
Cc: Rees, Nick (DLSLtd,RAL,DIA)
Subject: Re: EPICS internals talks?
 
Hi Nick,

On Wednesday 29 December 2010 08:11:12 nick.rees@diamond.ac.uk 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 
slides 40-50.

- Andrew
-- 
If a man is offered a fact which goes against his instincts, he will
scrutinize it closely, and unless the evidence is overwhelming, he will
refuse to believe it.  If, on the other hand, he is offered something
which affords a reason for acting in accordance to his instincts, he
will accept it even on the slightest evidence.  -- Bertrand Russell



-- 
This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail.
Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. 
Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message.
Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom
 





References:
Re: EPICS internals talks? Andrew Johnson

Navigate by Date:
Prev: event ordering Jeff Hill
Next: build system change for visual studio Jeff Hill
Index: 2002  2003  2004  2005  2006  2007  2008  2009  2010  <20112012  2013  2014  2015  2016  2017  2018  2019 
Navigate by Thread:
Prev: Re: EPICS internals talks? Andrew Johnson
Next: RE: EPICS internals talks? Jeff Hill
Index: 2002  2003  2004  2005  2006  2007  2008  2009  2010  <20112012  2013  2014  2015  2016  2017  2018  2019 
ANJ, 02 Feb 2012 Valid HTML 4.01! · Home · News · About · Base · Modules · Extensions · Distributions · Download ·
· Search · EPICS V4 · IRMIS · Talk · Bugs · Documents · Links · Licensing ·