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Timestamp now running late

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Mark Plas

Timestamp now running late

Hi,

I’m having a problem with ‘Timestamp now’. When I start up an image and I evaluate this expression, I get the correct date and time up to the level of seconds. When I leave the image running for several hours and I evaluate the expression again, I get a timestamp that is running late compared to my system time. I haven’t done any exact measurements yet but I have the impression that after 1 hour the clock runs late for about 5 or 6 seconds, after +/- 5 hours it runs late for 30 seconds. This occurs in vw7.3 and vw7.4.1. I’m running on windows XP.

Has anybody experienced this also ? and is there a known fix it ?

Thanks,

Mark

kobetic

Re: Timestamp now running late

This sounds a lot like AR#48495: "Sync clock to walltime (Was: Toggle between -walltime and HPC from image)", which was fixed in 7.4. Are you sure that you still have the problem in 7.4.1 ?

Mark Plas wrote:

> Hi,
>
>
>
> I’m having a problem with ‘Timestamp now’. When I start up an image and
> I evaluate this expression, I get the correct date and time up to the
> level of seconds. When I leave the image running for several hours and I
> evaluate the expression again, I get a timestamp that is running late
> compared to my system time. I haven’t done any exact measurements yet
> but I have the impression that after 1 hour the clock runs late for
> about 5 or 6 seconds, after +/- 5 hours it runs late for 30 seconds.
> This occurs in vw7.3 and vw7.4.1. I’m running on windows XP.
>
>
>
> Has anybody experienced this also ? and is there a known fix it ?
>
>
>
> Thanks,
>
> Mark
>

Holger Kleinsorgen-4

Re: Timestamp now running late

In reply to this post by Mark Plas

Mark Plas wrote:

> I'm having a problem with 'Timestamp now'. When I start up an image and
> I evaluate this expression, I get the correct date and time up to the
> level of seconds. When I leave the image running for several hours and I
> evaluate the expression again, I get a timestamp that is running late
> compared to my system time. I haven't done any exact measurements yet
> but I have the impression that after 1 hour the clock runs late for
> about 5 or 6 seconds, after +/- 5 hours it runs late for 30 seconds.
> This occurs in vw7.3 and vw7.4.1. I'm running on windows XP.
>
> Has anybody experienced this also ? and is there a known fix it ?

there's a VM command line switch, see AppDevGuide.pdf:

" On MS Windows systems, this switch is supported:
-walltime
Use the lower-resolution GetSystemTimeAsFileTime instead of
QueryPerformanceCounter to drive the microsecond clock. This is
useful for long-running applications that are very time sensitive, since
the default QueryPerformanceCounter, while higher-resolution, tends
to drift from the wall clock over a period of hours."

Thomas Brodt

RE: Timestamp now running late

In reply to this post by Mark Plas

I have this difference, too, but slightly worse. With me, it is half of the time that has been dumped not just some seconds. If I
run an image for 4 hours and then ask for a Timestamp now, I get 2 hours after the start time of the image. This can lead to quite
confusing time issues.
the cause may be the high performance clock counter (forgot the exact name, Eliot surely knows it) that is used for it which needs
to be realigned with the system from time to time because it is higher in precision but tends to drift.
You can try starting the vm with the -walltime flag and see if the effect disappears. Then this high performance counter is not used
and the time should be more stable, but lower in resolution.

HTH

Thomas

> -----Original Message-----
> From: Mark Plas [mailto:[hidden email]]
> Sent: Wednesday, November 29, 2006 3:44 PM
> To: [hidden email]
> Subject: Timestamp now running late
>
> Hi,
>
>
>
> I'm having a problem with 'Timestamp now'. When I start up an
> image and I evaluate this expression, I get the correct date
> and time up to the level of seconds. When I leave the image
> running for several hours and I evaluate the expression
> again, I get a timestamp that is running late compared to my
> system time. I haven't done any exact measurements yet but I
> have the impression that after 1 hour the clock runs late for
> about 5 or 6 seconds, after +/- 5 hours it runs late for 30
> seconds. This occurs in vw7.3 and vw7.4.1. I'm running on windows XP.
>
>
>
> Has anybody experienced this also ? and is there a known fix it ?
>
>
>
> Thanks,
>
> Mark
>
>

Thomas Brodt

RE: Timestamp now running late

Forgot to mention that my problem described below is with 7.3.1.

I have not upgraded to 7.4.1 yet (sigh), but as Martin already said, it seems to solve the issue, at least for me.

Thomas

> -----Original Message-----
> From: Thomas Brodt [mailto:[hidden email]]
> Sent: Wednesday, November 29, 2006 3:51 PM
> To: 'Mark Plas'; [hidden email]
> Subject: RE: Timestamp now running late
>
> I have this difference, too, but slightly worse. With me, it
> is half of the time that has been dumped not just some seconds. If I
> run an image for 4 hours and then ask for a Timestamp now, I
> get 2 hours after the start time of the image. This can lead to quite
> confusing time issues.
> the cause may be the high performance clock counter (forgot
> the exact name, Eliot surely knows it) that is used for it which needs
> to be realigned with the system from time to time because it
> is higher in precision but tends to drift.
> You can try starting the vm with the -walltime flag and see
> if the effect disappears. Then this high performance counter
> is not used
> and the time should be more stable, but lower in resolution.
>
> HTH
>
> Thomas
>
> > -----Original Message-----
> > From: Mark Plas [mailto:[hidden email]]
> > Sent: Wednesday, November 29, 2006 3:44 PM
> > To: [hidden email]
> > Subject: Timestamp now running late
> >
> > Hi,
> >
> >
> >
> > I'm having a problem with 'Timestamp now'. When I start up an
> > image and I evaluate this expression, I get the correct date
> > and time up to the level of seconds. When I leave the image
> > running for several hours and I evaluate the expression
> > again, I get a timestamp that is running late compared to my
> > system time. I haven't done any exact measurements yet but I
> > have the impression that after 1 hour the clock runs late for
> > about 5 or 6 seconds, after +/- 5 hours it runs late for 30
> > seconds. This occurs in vw7.3 and vw7.4.1. I'm running on
> windows XP.
> >
> >
> >
> > Has anybody experienced this also ? and is there a known fix it ?
> >
> >
> >
> > Thanks,
> >
> > Mark
> >
> >
>
>

Travis Griggs-3

Re: Timestamp now running late

In reply to this post by Thomas Brodt

On Nov 29, 2006, at 6:51, Thomas Brodt wrote:

I have this difference, too, but slightly worse. With me, it is half of the time that has been dumped not just some seconds. If I
run an image for 4 hours and then ask for a Timestamp now, I get 2 hours after the start time of the image. This can lead to quite
confusing time issues.
the cause may be the high performance clock counter (forgot the exact name, Eliot surely knows it) that is used for it which needs
to be realigned with the system from time to time because it is higher in precision but tends to drift.
You can try starting the vm with the -walltime flag and see if the effect disappears. Then this high performance counter is not used
and the time should be more stable, but lower in resolution.

I'm not proposing this as a fix (necessarily), but I am curious how it behaves in such an environment. Load version 21 of OSTimeZone from Open Repository (some/all of the later versions appear to have broken this feature). Execute:

OSSystemSupportTimeZone use

Then do your Timestamp queries. I imagine they'll still drift, but I'm curious anyway.

Travis Griggs

Objologist

One man's blue plane is another man's pink plane.

Mark Plas

Timestamp now running late

In reply to this post by Mark Plas

Thanks for the replies,

I'm now running an experiment in vw7.4.1 and I've noticed the following:

- at first the timestamp is correct and stays correct for at least 15
minutes
- suddenly, the vw clock runs 4 seconds fast
- a few minutes later, the clock runs correct again

I'm going to keep it running for a while and see how it behaves. If it
'resynchronizes' every xx minutes, that would be good enough for me.

We're currently using vw7.3 but are planning to upgrade to 7.4.1.

-----Original Message-----
From: Thomas Brodt [mailto:[hidden email]]
Sent: woensdag 29 november 2006 16:25
To: [hidden email]
Subject: RE: Timestamp now running late

Forgot to mention that my problem described below is with 7.3.1.

I have not upgraded to 7.4.1 yet (sigh), but as Martin already said, it
seems to solve the issue, at least for me.

Thomas

Dennis smith-4

Re: Timestamp now running late

Mark Plas wrote:

 

Thanks for the replies,

I'm now running an experiment in vw7.4.1 and I've noticed the following:

- at first the timestamp is correct and stays correct for at least 15
minutes
- suddenly, the vw clock runs 4 seconds fast
- a few minutes later, the clock runs correct again

I'm going to keep it running for a while and see how it behaves. If it
'resynchronizes' every xx minutes, that would be good enough for me.

If it gets that far out that fast, I am not happy with it. If it was out by 1/2sec after an hour, maybe.

We're currently using vw7.3 but are planning to upgrade to 7.4.1.

-----Original Message-----
From: Thomas Brodt [[hidden email]] 
Sent: woensdag 29 november 2006 16:25
To: [hidden email]
Subject: RE: Timestamp now running late

Forgot to mention that my problem described below is with 7.3.1. 

I have not upgraded to 7.4.1 yet (sigh), but as Martin already said, it
seems to solve the issue, at least for me.

Thomas

-----Original Message-----
From: Thomas Brodt [[hidden email]] 
Sent: Wednesday, November 29, 2006 3:51 PM
To: 'Mark Plas'; [hidden email]
Subject: RE: Timestamp now running late

I have this difference, too, but slightly worse. With me, it 
is half of the time that has been dumped not just some seconds.  If I
run an image for 4 hours and then ask for a Timestamp now, I 
get 2 hours after the start time of the image. This can lead to quite
confusing time issues.
the cause may be the high performance clock counter (forgot 
the exact name, Eliot surely knows it) that is used for it which needs
to be realigned with the system from time to time because it 
is higher in precision but tends to drift.
You can try starting the vm with the -walltime flag and see 
if the effect disappears. Then this high performance counter 
is not used
and the time should be more stable, but lower in resolution.

HTH

Thomas

-----Original Message-----
From: Mark Plas [[hidden email]] 
Sent: Wednesday, November 29, 2006 3:44 PM
To: [hidden email]
Subject: Timestamp now running late

Hi,

I'm having a problem with 'Timestamp now'. When I start up an 
image and I evaluate this expression, I get the correct date 
and time up to the level of seconds. When I leave the image 
running for several hours and I evaluate the expression 
again, I get a timestamp that is running late compared to my 
system time. I haven't done any exact measurements yet but I 
have the impression that after 1 hour the clock runs late for 
about 5 or 6 seconds, after +/- 5 hours it runs late for 30 
seconds. This occurs in vw7.3 and vw7.4.1. I'm running on

windows XP.

 

Has anybody experienced this also ? and is there a known fix it ?

 

Thanks,

Mark

-- 
Dennis Smith                        [hidden email]
Cherniak Software Development Corporation       +1 905.771.7011
400-10 Commerce Valley Dr E                Fax: +1 905.771.6288
Thornhill, ON Canada L3T 7N7    http://www.CherniakSoftware.com

Dennis smith-4

Re: Timestamp now running late

In reply to this post by Mark Plas

Mark Plas wrote:

 

Thanks for the replies,

I'm now running an experiment in vw7.4.1 and I've noticed the following:

- at first the timestamp is correct and stays correct for at least 15
minutes
- suddenly, the vw clock runs 4 seconds fast
- a few minutes later, the clock runs correct again

I'm going to keep it running for a while and see how it behaves. If it
'resynchronizes' every xx minutes, that would be good enough for me.

On second thought, after my first reply here, that significant resync is not acceptable no matter how often
or hour little. If I grab a timestamp twice, say 2sec apart, it better be in the correct order (the second MUST
be later than the first).

We're currently using vw7.3 but are planning to upgrade to 7.4.1.

-----Original Message-----
From: Thomas Brodt [[hidden email]] 
Sent: woensdag 29 november 2006 16:25
To: [hidden email]
Subject: RE: Timestamp now running late

Forgot to mention that my problem described below is with 7.3.1. 

I have not upgraded to 7.4.1 yet (sigh), but as Martin already said, it
seems to solve the issue, at least for me.

Thomas

-----Original Message-----
From: Thomas Brodt [[hidden email]] 
Sent: Wednesday, November 29, 2006 3:51 PM
To: 'Mark Plas'; [hidden email]
Subject: RE: Timestamp now running late

I have this difference, too, but slightly worse. With me, it 
is half of the time that has been dumped not just some seconds.  If I
run an image for 4 hours and then ask for a Timestamp now, I 
get 2 hours after the start time of the image. This can lead to quite
confusing time issues.
the cause may be the high performance clock counter (forgot 
the exact name, Eliot surely knows it) that is used for it which needs
to be realigned with the system from time to time because it 
is higher in precision but tends to drift.
You can try starting the vm with the -walltime flag and see 
if the effect disappears. Then this high performance counter 
is not used
and the time should be more stable, but lower in resolution.

HTH

Thomas

-----Original Message-----
From: Mark Plas [[hidden email]] 
Sent: Wednesday, November 29, 2006 3:44 PM
To: [hidden email]
Subject: Timestamp now running late

Hi,

I'm having a problem with 'Timestamp now'. When I start up an 
image and I evaluate this expression, I get the correct date 
and time up to the level of seconds. When I leave the image 
running for several hours and I evaluate the expression 
again, I get a timestamp that is running late compared to my 
system time. I haven't done any exact measurements yet but I 
have the impression that after 1 hour the clock runs late for 
about 5 or 6 seconds, after +/- 5 hours it runs late for 30 
seconds. This occurs in vw7.3 and vw7.4.1. I'm running on

windows XP.

 

Has anybody experienced this also ? and is there a known fix it ?

 

Thanks,

Mark

-- 
Dennis Smith                        [hidden email]
Cherniak Software Development Corporation       +1 905.771.7011
400-10 Commerce Valley Dr E                Fax: +1 905.771.6288
Thornhill, ON Canada L3T 7N7    http://www.CherniakSoftware.com

kobetic

Re: Timestamp now running late

Dennis Smith wrote:
> On second thought, after my first reply here, that significant resync is
> not acceptable no matter how often
> or hour little. If I grab a timestamp twice, say 2sec apart, it better
> be in the correct order (the second MUST
> be later than the first).

I don't know the details, but monotonicity was a requirement, so if we have a case where it isn't true, that would constitute a bug.

Mark Plas

RE: Timestamp now running late

In reply to this post by Mark Plas

I did some more testing in vw7.4.1. Here’s what I do:

- I start up an image (without –walltime)

- In a workspace I evaluate ‘Timestamp now’ and it shows the same time as windows xp does

- I leave the image open and every once in a while I reevaluate ‘Timestamp now’. Mostly it returns the correct time.

- But sometimes the time is running late for 45 seconds (this figure is a bit random, and sometimes it runs fast).

- When I then evaluate ‘Timestamp now’ again, I get the correct time again.

To me it seems that a ‘synchronisation’ happens after ‘Timestamp now’ is being executed.

From: Dennis Smith [mailto:[hidden email]]
Sent: woensdag 29 november 2006 17:45
To: Mark Plas
Cc: [hidden email]
Subject: Re: Timestamp now running late

Mark Plas wrote:

Thanks for the replies,

I'm now running an experiment in vw7.4.1 and I've noticed the following:

- at first the timestamp is correct and stays correct for at least 15

minutes

- suddenly, the vw clock runs 4 seconds fast

- a few minutes later, the clock runs correct again

I'm going to keep it running for a while and see how it behaves. If it

'resynchronizes' every xx minutes, that would be good enough for me.

We're currently using vw7.3 but are planning to upgrade to 7.4.1.

-----Original Message-----

From: Thomas Brodt [[hidden email]]

Sent: woensdag 29 november 2006 16:25

To: [hidden email]

Subject: RE: Timestamp now running late

Forgot to mention that my problem described below is with 7.3.1.

I have not upgraded to 7.4.1 yet (sigh), but as Martin already said, it

seems to solve the issue, at least for me.

Thomas

-----Original Message-----

From: Thomas Brodt [[hidden email]]

Sent: Wednesday, November 29, 2006 3:51 PM

To: 'Mark Plas'; [hidden email]

Subject: RE: Timestamp now running late

I have this difference, too, but slightly worse. With me, it

is half of the time that has been dumped not just some seconds.  If I

run an image for 4 hours and then ask for a Timestamp now, I

get 2 hours after the start time of the image. This can lead to quite

confusing time issues.

the cause may be the high performance clock counter (forgot

the exact name, Eliot surely knows it) that is used for it which needs

to be realigned with the system from time to time because it

is higher in precision but tends to drift.

You can try starting the vm with the -walltime flag and see

if the effect disappears. Then this high performance counter

is not used

and the time should be more stable, but lower in resolution.

HTH

Thomas

-----Original Message-----

From: Mark Plas [[hidden email]]

Sent: Wednesday, November 29, 2006 3:44 PM

To: [hidden email]

Subject: Timestamp now running late

Hi,

I'm having a problem with 'Timestamp now'. When I start up an

image and I evaluate this expression, I get the correct date

and time up to the level of seconds. When I leave the image

running for several hours and I evaluate the expression

again, I get a timestamp that is running late compared to my

system time. I haven't done any exact measurements yet but I

have the impression that after 1 hour the clock runs late for

about 5 or 6 seconds, after +/- 5 hours it runs late for 30

seconds. This occurs in vw7.3 and vw7.4.1. I'm running on

windows XP.

Has anybody experienced this also ? and is there a known fix it ?

Thanks,

Mark

--

Dennis Smith                        [hidden email]

Cherniak Software Development Corporation       +1 905.771.7011

400-10 Commerce Valley Dr E                Fax: +1 905.771.6288

Thornhill, ON Canada L3T 7N7    http://www.CherniakSoftware.com