RE: Remaining free buffers in an AD plugin queue

[Mark Rivers <rivers@cars.uchicago.edu>]

That sounds like a good idea.  I'll try to do it for the next release.  I don't think it should be hard.

I'll also look into making available the number of buffer and memory in the pool, assuming a driver/plugin has established a limit on those.

Mark

________________________________________
From: tech-talk-bounces@aps.anl.gov [tech-talk-bounces@aps.anl.gov] on behalf of Emma Shepherd [Emma.Shepherd@synchrotron.org.au]
Sent: Wednesday, August 08, 2012 10:52 PM
To: tech-talk@aps.anl.gov
Subject: Remaining free buffers in an AD plugin queue

Hello AreaDetector experts,

I'm wondering if there is a way to find out at runtime how many free buffers a particular plugin has left in its queue.  In our application, the file writing plugin cannot be blocking since the acquisition from the camera must not be held up, but at the same time I need to ensure that it does not drop any frames.  What we would like to be able to do is time the start of each acquisition run so that the file plugin has caught up sufficiently, but without waiting any longer than absolutely necessary.

I know there is an ArrayCounter record in both ADBase.template and NDPluginBase.template, so in theory I think the (detector.ArrayCounter - plugin.ArrayCounter) = number of used buffers, assuming they were both reset at the same point.  I guess I could put some logic in the database to check this, but to calculate how many are remaining it would have to know the queue size that was allocated to the plugin in the startup script.  I thought it would be handy if the plugin driver could expose the number of free buffers as an asyn parameter instead.

I'd be glad to hear any thoughts on this, has anyone else tried to do something similar?

Thanks,
Emma