[ltt-dev] Problem with tracing network events in 0.128 to 0.132

Mathieu Desnoyers compudj at krystal.dyndns.org
Tue May 5 13:27:07 EDT 2009

* Gregory Haskins (ghaskins at novell.com) wrote:
> Mathieu Desnoyers wrote:
> > * Gregory Haskins (ghaskins at novell.com) wrote:
> >   
> >>
> >> I am willing to dig in and see if I can fix it, but I figured I would
> >> post first to see if this is a known issue, has a workaround, or perhaps
> >> some guiding wisdom on what to look for first.
> >>
> >>     
> >
> > Hi Greg,
> >
> > It should be fixed in LTTng 0.133. Can you confirm ?
> >   
> Hi Mathieu,
>   I confirmed that the ethernet IRQ is now showing up.  Thanks!  Note,
> however, that the softirq-net-rx (softirq-3) is still notably missing. 
> Is there a similar issue on the softirq side?  Note that I do see some
> of the softirq vectors (1, 6, and 8 specifically), so its not a general
> problem.

Hi Greg,

Hrm, which events are missing for softirq-net-rx exactly ? only softirq
raise or also softirq entry/exit ?

I know I need to update my softirq raise instrumentation. Should be done
soon, but I wonder about entry/exit.

> As an aside, note that ive been seeing a problem in lttv-gui for a while
> now where the interrupts/softirqs can sometimes get "stuck".  (e.g. the
> color bar goes to infinity even if there are no events).  I suspect that
> part of the problem is perhaps overlapping events when you allow things
> like interrupts to preempt each other.  As an additional datapoint, I do
> not see the problem when I turn on lockdep, which disables overlapping
> interrupts.

Hrm, in which view do you have this problem ? The per-thread control
flow view or the ressource view ?

> In case I have not said it enough in the past, LTTng rocks, so thanks
> for all the work here.

You are very welcome. :) Thanks for this useful feedback.


> -Greg

Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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