dtrace discuss - Jun 2008 - Inconsistent timestamps in DTrace output

Hi,

 

We''re having problems with some of the timestamps produced by dtrace
where they seem to be roughly doubled (the following snippet is from the
attached log file):

 

3037095639860141 on-cpu 1 4 59

3037095639864555 off-cpu 1 

3037095649855777 on-cpu 1 4 59

3037095650461752 off-cpu 1 

6074193317343753 on-cpu 1 1 59

6074193318047271 off-cpu 1 

3037096589857081 on-cpu 1 4 59

3037096589861755 off-cpu 1 

 

The attached script file (''t'') was used to produce the output
and we
used vmstat for the test. (> t vmstat )

 

We''re using HP 585 G2 (4CPU dual core AMD Opteron) boxes running
Solaris
10 update 3.

 

Is this a known issue? Is there a fix?

 

Cheers,

Andrew

 

 

 

 

 

 

 


Andrew Addison

BJSS Ltd., 1st Floor, Coronet House, Queen Street, Leeds, LS1 2TW

Tel: +44 (113) 297 9797

Fax: +44 (113) 297 9798

Website: www.bjss.co.uk <http://www.bjss.co.uk/> 

Email: andrew.addison at bjss.co.uk

RM: andrew.addison.bjss.co.uk at reuters.net

 



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Hey Andrew,
> We''re having problems with some of the timestamps produced by
dtrace
> where they seem to be roughly doubled (the following snippet is from the
> attached log file):
> 
>  
> 
> 3037095639860141 on-cpu 1 4 59
> 
> 3037095639864555 off-cpu 1 
> 
> 3037095649855777 on-cpu 1 4 59
> 
> 3037095650461752 off-cpu 1 
> 
> 6074193317343753 on-cpu 1 1 59
> 
> 6074193318047271 off-cpu 1 
> 
> 3037096589857081 on-cpu 1 4 59
> 
> 3037096589861755 off-cpu 1 
> 
>  
> 
> The attached script file (''t'') was used to produce the
output and we
> used vmstat for the test. (> t vmstat )
This looks an awful lot like:

  6600939 gethrtime sometimes return a large time value into the future

This can have -- for arcane reasons -- symptoms that include the doubling
that you''re seeing.  This bug is fixed in Nevada (Build 77) and the fix
will also be in S10 Update 6...

	- Bryan

--------------------------------------------------------------------------
Bryan Cantrill, Sun Microsystems Fishworks.       http://blogs.sun.com/bmc

The fix for 6600939 is also now available in a kernel patch for pre S10u6
systems:

 137112-01  SunOS 5.10_x86: kernel patch Date: Jun/10/2008
 137111-01  SPARC version

Cheers,
David Holmes


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