Experimental Physics and
Industrial Control System

Mark Rivers <[email protected]> · Wed, 18 Dec 2013 19:15:50 +0000

What EPICS record, and how did you measure that?  Something is very wrong.

Here is a paper with performance measurements on an ancient (~20 years ago) 68040 that shows only 150 microseconds was required for a bi record, including posting a CA monitor.

http://www.aps.anl.gov/epics/EpicsDocumentation/EpicsGeneral/epicsX5Farch-1.html#HEADING1-23

Mark

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Evgeniy
Sent: Wednesday, December 18, 2013 1:07 PM
To: Eric Norum
Cc: EPICS Tech Talk
Subject: Re: Increasing scan rate to 10 kHz

Processing of an EPICS record takes ~2 milliseconds on my SL5.3/DELL 
2.27 GHz. It is unbelievably slow!
Is it possible to shorten this time without rebuilding Linux kernel?

-------- Original Message --------
> On Nov 27, 2013, at 11:29 AM, Evgeniy <[email protected]> wrote:
>
>> Thanks, Andrew and Emmanuel for your replies.
>>
>> I am running Soft IOC on Dell server (64 bit) with eight  Intel Xeon CPUs, each  2.27GHz.
>> It seems that syntax for dbd file is correct. I found that minimum scan period for my system is 0.001 seconds. For shorter periods it falls down to 0.1 second, as Andrew mentioned.
>> The difference in one CPU usage is only 5% if I run records with scan 0.1 second or 0.001 second. It looks like it is limitation of EPICS, not hardware.
> Or perhaps the kernel timer implementation has a resolution of 1 ms?
>>   What is the bottleneck for processing of a record on GHz CPUs?
>> Is it possible to improve it?
>>
>> Evgeniy

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System