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Subject: Re: EPICS base V4
From: Eric Norum <[email protected]>
To: Andrew Johnson <[email protected]>
Cc: Ned Arnold <[email protected]>, Benjamin Franksen <[email protected]>, Marty Kraimer <[email protected]>, Jeff Hill <[email protected]>, Ralph Lange <[email protected]>, Bob Dalesio <[email protected]>, Matej Sekoranja <[email protected]>
Date: Fri, 25 Feb 2005 12:49:15 -0600

On Feb 25, 2005, at 11:25 AM, Andrew Johnson wrote:

Responding to these comments in the order they were made:

Ralph Lange wrote:
Does this imply that IOC load is evenly distributed? I.e. that records with the same scanPeriod period are processed in a "spread over time" manner rather than "en bloc" as in V3?

I suspect that's how it would behave, although I'm not 100% sure how we should be measuring the delay period - presumably measured from the start time of the previous record processing (i.e. we'd add another timestamp field in dbCommon to record the start of processing time, although we could just start the processing delay time from the *end* of the previous processing). If we do it that way then records of the same period would get spread out over time by the delays between their timer going off and actually getting processed.

I'd like to register a strong objection to this since it means that the 'sampling rate' of periodic record processing is no longer deterministic. I think that it is much more important that the long-term average rate of periodic record processing match the specified rate.

--
Eric Norum <[email protected]>
Advanced Photon Source
Argonne National Laboratory
(630) 252-4793



References:
Re: EPICS base V4: iocCore database Marty Kraimer
Re: EPICS base V4: iocCore database Andrew Johnson
Re: EPICS base V4: iocCore database: Booleans Benjamin Franksen
EPICS base V4 Marty Kraimer
Re: EPICS base V4 Andrew Johnson
Re: EPICS base V4 Ralph Lange
Re: EPICS base V4 Andrew Johnson

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