On Thu, 8 Nov 2018 at 18:31, Alok Priyadarshi <alo...@gmail.com> wrote: > > Jonathan: The system is x86_64, 16 cores, no cpu affinity set. Not too sure > about load yet. > > Mathieu: The explanation makes sense. Running babeltrace with > --stream-intersection flag did filter out a lot of events. However it is hard > to verify the filtered result because we do not yet know how to read the text > format. Does the babeltrace python API support stream intersection by any > chance?
Hi Alok, The TraceCollection constructor accepts an "intersect_mode" parameter which will provide the same semantics as --stream-intersection. Regards, Jérémie > > > On Thu, Nov 8, 2018 at 9:52 AM Mathieu Desnoyers > <mathieu.desnoy...@efficios.com> wrote: >> >> Hi Alok, >> >> With a snapshot trace, you can end up with some per-cpu buffers that contain >> information >> going further back in time compared to other per-cpu buffers. This depends >> on the level of >> system activity and tracing throughput for each CPU. >> >> The situation you experience can very well be triggered by having the begin >> event on one CPU, >> being migrated to another CPU, and having the end event on another CPU. If >> either the >> source or destination CPU has been more active than the other, you may find >> that you >> have only the begin or the end event in your trace. >> >> This is why we implemented the "stream intersection" mode in babeltrace. It >> ensures that >> babeltrace cuts away trace data belonging to time spans that only appear in >> some of >> the streams. It is not however activated by default. >> >> To try it out, you can do this: >> >> babeltrace --stream-intersection path/to/trace >> >> Does it help ? >> >> Thanks, >> >> Mathieu >> >> ----- On Nov 7, 2018, at 7:12 PM, Alok Priyadarshi <alo...@gmail.com> wrote: >> >> A custom trace event class emits "begin" and "end" events in its constructor >> and destructor respectively. So I do not think this is due to conditional >> path. >> >> Sequence of commands to capture a snapshot are: >> lttng create --snapshot >> lttng enable-event --userspace --all >> lttng add-context --userspace -t vpid -t vtid >> lttng start >> lttng stop >> lttng snapshot record >> >> We create a new session for each snapshot to make sure that the buffer does >> not have any left-over events from the previous session. But I am curious if >> lttng shares buffers between sessions or re-uses buffers from an old session >> without flushing? >> >> Note that I am using the default LTTNG_BUFFER_PER_UID mode. All processes >> for our application run under one UID, and only one tracing session is >> active at a time. >> >> On Wed, Nov 7, 2018 at 12:09 PM Jonathan Rajotte-Julien >> <jonathan.rajotte-jul...@efficios.com> wrote: >>> >>> Hi Alok, >>> >>> On Wed, Nov 07, 2018 at 11:53:25AM -0800, Alok Priyadarshi wrote: >>> > Hi Jonathan, >>> > >>> > Thanks for your response. >>> > >>> > We are tracing function scopes. Each scope emits two events - begin and >>> > end. We noticed that some begin events did not have corresponding end >>> > events in the trace. >>> >>> Seems like a solid ground as long as the corresponding ending event is not >>> inside any conditional paths. I'm sure you already validated that but we >>> never >>> know. >>> >>> > >>> > I have the trace with this problem available. Would that provide any clue? >>> >>> It could help but I presume it might contains confidential or sensible >>> information. Let's define the scenario first and we will go back to actual >>> trace data if needed. >>> >>> > If not, I will try to extract a small reproducer. >>> >>> That would be best. In the meantime, could you provide the exact lttng >>> commands >>> used to setup everything and describe subsequent lttng commands used for >>> snapshot etc. >>> >>> You can omit event name or replace them with dummy name if necessary. >>> >>> Cheers >>> >>> -- >>> Jonathan Rajotte-Julien >>> EfficiOS >> >> >> _______________________________________________ >> lttng-dev mailing list >> lttng-dev@lists.lttng.org >> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev >> >> >> -- >> Mathieu Desnoyers >> EfficiOS Inc. >> http://www.efficios.com > > _______________________________________________ > lttng-dev mailing list > lttng-dev@lists.lttng.org > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -- Jérémie Galarneau EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
