----- Original Message ----- > From: "Jérémie Galarneau" <[email protected]> > To: "zlynus" <[email protected]> > Cc: "lttng-dev" <[email protected]> > Sent: Friday, March 7, 2014 1:23:01 PM > Subject: Re: [lttng-dev] Can tracepoint be listed before app registered? > > On Fri, Mar 7, 2014 at 12:26 PM, zlynus <[email protected]> wrote: > > Hi, > > Sorry to bother you guys. The lttng-tool man page dosen't make it clear > > that > > when the tracepoints of user-space application can be listed. So I did a > > little test. As far as I can tell ,the tracepoint information is only > > available during the application is running. > > > > Correct. > > > So is it possible that the tracepoint can be available *before* app get > > running, specifically, before enable-event subcommand? I think it can be > > quite convenient to output the list when specify which events to trace. If > > it is not for now, > > maybe it's a feature worth working on. My idea is lttng-tool could read > > tracer provider library and get the info,and add a option after 'list' > > subcommand which let user specify the provider library to read. Just a > > personal opion from a new comer :-) > > > > You can enable an event before the app is started. However, as you > pointed out, the session daemon has no knowledge of application events > before they are launched. > > My understanding of your suggestion is that we should define a public > provider API on which the lttng client could hook itself to list > events. It would be of limited use in the case of statically linked > providers, but It's an interesting problem... Do you have a specific > use-case in mind?
Another option that would take care of statically linked providers would be to let a lttng library look at all the executables on the system (or from a certain path in the system), as well as .so, and list a specific "tracepoint provider" section that we could specify. We'd need to parse ELF for this. Thoughts ? Thanks, Mathieu > > Regards, > Jérémie > > > Best regards, > > Lingyu Zhu > > > > > > _______________________________________________ > > lttng-dev mailing list > > [email protected] > > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > > > > > > -- > Jérémie Galarneau > EfficiOS Inc. > http://www.efficios.com > > _______________________________________________ > lttng-dev mailing list > [email protected] > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
