Experimental Physics and
Industrial Control System

"Jeff Hill" <[email protected]> · Thu, 3 Feb 2011 16:45:40 -0700

> The Windows version of osdTime.cpp prints that message if it sees time
> going backwards.  

There is also a recent confirmed bug entry in Mantis related to that code.

https://bugs.launchpad.net/epics-base/+bug/697509

Jeff
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Jeffrey O. Hill           Email        [email protected]
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Message content: TSPA

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not necessarily a good idea. It is hard to be sure where they
are going to land, and it could be dangerous sitting under them
as they fly overhead. -- RFC 1925

> -----Original Message-----
> From: [email protected] [mailto:tech-talk-
> [email protected]] On Behalf Of Andrew Johnson
> Sent: Thursday, February 03, 2011 3:14 PM
> To: [email protected]; [email protected]
> Subject: Re: time discontinuity detected
> 
> Hi Carsten,
> 
> On Wednesday 02 February 2011 06:01:14 Carsten Winkler (HZB) wrote:
> > Epics time goes crazy if I run softIoc with Epics base 3.14.12 (with
> all
> > official patches) in a virtual machine.
> >
> > I use following configuration:
> >                        Hypervisor:   kvm
> >                        Architecture: x86_64
> >                        Guest:        Windows XP (32-bit)
> >
> > All works fine if I use a single core VM.
> >
> > But if I use two or more CPU cores Epics time does several funny
> actions.
> > * I also get events with a new value but previous time stamp.
> > * Timestamps are wrong and in the future.
> > * I get the message: "currentTime::getCurrentTime(): 7623636.000000sec
> time
> > discontinuity detected".
> 
> The Windows version of osdTime.cpp prints that message if it sees time
> going
> backwards.  The code uses a tries to improve the resolution with which it
> sees
> the current time using WIN32 high resolution performance counters, and it
> appears that this approach is not compatible with the use of a multi-core
> virtual machine.  This is the "PerfCounter" Current Time Provider that
> you
> should currently see listed in the output from the IOC's
> generalTimeReport
> command.
> 
> EPICS Base does allow you to register and use your own time providers
> though,
> so if you can identify a better approach for obtaining accurate high-
> resolution time from within a multi-core VM it is possible to write and
> install your own alternative to the built-in provider without having to
> make
> any changes to EPICS Base.
> 
> - 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

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System