perfSONAR User Q&A and Other Discussion

[Aaron Brown <>]

Hey Brian,

> On Dec 10, 2014, at 7:04 PM, Brian Candler 
> <>
>  wrote:
> 
> I made little headway in narrowing this down.
> 
> I added some debugging in bwctl.c wait_for_results. When the total test 
> times were ~45 seconds, I was able to see that the difference between the 
> req_time and the current time was 35 seconds (but duration=10, omit=0, 
> fuzz=just over 1 second). So it's something to do with calculating the 
> future request time.
> 
> I have also seen cases of wait_for_results saying times of over 80 seconds.

That’s just bizarre. These hosts weren’t running NTP, right? I can only guess 
that bwctl is doing something funky with error estimates when NTP isn’t 
running.

> 
> I then added further debugging, but by the time I did this, it was back to 
> "working" again - 15 seconds per test :-(
> 
> At bwctl client side:
> 
> bwctl: BWLGetTimeStamp: errest=2100000
> bwctl: BWLSetTimeStampError: val=9019431321
> bwctl: BWLSetTimeStampError: scale=26, multiplier=135
> bwctl: BWLGetTimeStamp: errest=2100000
> bwctl: BWLSetTimeStampError: val=9019431321
> bwctl: BWLSetTimeStampError: scale=26, multiplier=135
> 
> That's fine: 0.1 is the default skew estimate, and I put -a 2 on the 
> command line.
> 
> On bwctld:
> 
> bwctld[16642]: FILE=time.c, LINE=395, BWLGetTimeStamp: errest=100000
> bwctld[16642]: FILE=time.c, LINE=718, BWLSetTimeStampError: val=429496729
> bwctld[16642]: FILE=time.c, LINE=736, BWLSetTimeStampError: scale=21, 
> multiplier=205
> bwctld[16642]: FILE=time.c, LINE=395, BWLGetTimeStamp: errest=100000
> bwctld[16642]: FILE=time.c, LINE=718, BWLSetTimeStampError: val=429496729
> bwctld[16642]: FILE=time.c, LINE=736, BWLSetTimeStampError: scale=21, 
> multiplier=205
> 
> This is all fine. 429496729.0/(1<<32) ~= 0.1 seconds.
> 
> I can only guess that in some circumstances large fuzz or offset values are 
> being used, but fiddling with BWCTL_DEBUG_TIMEOFFSET I am not able to 
> recreate the problem.
> 
> Unfortunately I'm running out of time now as (a) it's late, and (b) 
> tomorrow these boxes get shipped out :-(

Sorry we weren’t able to figure out the issue. Are these boxes going to be 
running NTP in the field? If so, hopefully that may fix things...

Cheers,
Aaron