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<== Date ==> <== Thread ==>
Subject: Re: Timing in seq record
From: Andrew Johnson via Tech-talk <tech-talk at aps.anl.gov>
To: Michael Davidsaver <mdavidsaver at gmail.com>, Mark Rivers <rivers at cars.uchicago.edu>
Cc: "tech-talk at aps.anl.gov" <tech-talk at aps.anl.gov>
Date: Thu, 3 Mar 2022 10:26:19 -0600
On 3/3/22 9:56 AM, Michael Davidsaver wrote:
On 3/3/22 05:21, Mark Rivers via Tech-talk wrote:
I believe Freddie is correct in his more recent message:

There were timers waking up early, but also half a quantum being subtracted from the time value asked for, I think to give a good average wakeup time for systems when wakeup is on boundaries of the quantum. I see that this subtraction still happens

This looks like a problem of quantum/2 subtraction.

I agree that this arbitrary shortening is a ~bug, but it is worth remembering
that my attempt at removing this it caused a problem for you (Mark) on vxworks.

https://bugs.launchpad.net/epics-base/+bug/1861612/comments/12

There are some known problems with using epicsTimer for precise, short, delays.

One thing Mark could try would be to set the sleep quantum to 0 on Linux. I've not looked at the code for ages so I don't know if it will cause other problems (please do a 'make runtests' after changing it to look for possible issues).

- Andrew

-- 
Complexity comes for free, Simplicity you have to work for.
References:
Timing in seq record Mark Rivers via Tech-talk
RE: Timing in seq record Mark Rivers via Tech-talk
Re: Timing in seq record Mark Rivers via Tech-talk
Re: Timing in seq record Johnson, Andrew N. via Tech-talk
Re: Timing in seq record Mark Rivers via Tech-talk
Re: Timing in seq record Michael Davidsaver via Tech-talk
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