[ltt-dev] Multi-second gaps in trace events
compudj at krystal.dyndns.org
Wed Sep 30 13:44:44 EDT 2009
OK. Then, other question, do you have warnings in your traced board
dmesg telling that you have "lost subbuffers" or lost events ? This is
shown right after tracing stops. (newer LTTng has this warning shown in
LTTV, but your old LTTng/LTTV combo doesn't)
Your buffer size may be too small.
Are you tracing in "overwrite" or "non-overwrite" mode ?
* Chad Willman (cwillman at lifesize.com) wrote:
> 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.
> 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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