[ltt-dev] Multi-second gaps in trace events

[Chad Willman]

Thanks for the reply.

Yes, it's an ARM, but it has a cycle-counter and we've actually added
support for it to LTTng. We get nanosecond resolution.

Chad 


On 9/30/09 12:29 PM, "Mathieu Desnoyers" <compudj at krystal.dyndns.org> wrote:

> * Chad Willman (cwillman at lifesize.com) wrote:
>> 
>> I¹m seeing long (multi-second) gaps in trace events and am wondering if this
>> is a known issue.
>> 
>> For example, trace events shown in the viewer appear normal and then
>> suddenly there will be a gap of 9 seconds (varies) where it appears that a
>> single thread is running in user mode (green) and nothing else is happening
>> on the entire system in any thread for 9 seconds (no context switches, . . .
>> nothing).
>> 
>> This is an excellent tracing facility, but I can¹t rely on it entirely until
>> I have no gaps in the trace. Any ideas ?
>> 
>> I¹m running -
>> Lttng v 0.6.33 on Linux 2.6.18 kernel on a TI DaVinci DM6467T SOC platform
> 
> That's an ARM board right ?
> 
> On these boards, LTTng has a 1 jiffy precision, because it uses the
> "generic clock". Within this interval, events are simply counted, e.g. 1
> cycle = 1 event.
> 
> The ARM OMAP3 has cycle counters, which LTTng uses.
> 
> Mathieu
> 
>> Ltt-control v 0.30
>> Lttv v 0.8.72
>> Genevent v 0.30
>> 
>> Regards,
>> 
>> CW
> 
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