----- Original Message ----- > From: "David Goulet" <[email protected]> > To: "Jim Dumont" <[email protected]> > Cc: [email protected] > Sent: Tuesday, February 4, 2014 12:17:36 PM > Subject: Re: [lttng-dev] lttng-dev Digest, Vol 67, Issue 48 > > On 17 Jan (17:26:13), Jim Dumont wrote: > > Hi there, > > > > Was there a follow-up to the series of questions raised by Daniel below and > > referenced here: > > > > http://lists.lttng.org/pipermail/lttng-dev/2013-November/021844.html > > > > I didn't see one in the mailing list. > > > > BR, > > > > /Jim > > > > > > > 1) Live support. It's now possible to stream traces (kernel and UST) > > > while they being extracted meaning a relayd can now receive traces > > > live and a viewer can attach to it to process the trace while running. > > > The "--live" has been added to lttng create command that sets up a > > > live tracing session. > > > > > > See doc/live-reading-howto.txt and doc/live-reading-protocol.txt for > > > more detail on that feature. > > > > Does this mean you can't do a "live" trace to local storage? > > You can use local storage for the live feature BUT you always need a > relayd thus there will be some streaming happening on the loopback > interface. > > However, you *can't* start a live viewer by directly pointing to a trace > on disk. It may works but we do NOT recommend it since you'll probably > end up in a bad state or have synchronization issue. > > > > > > 2) Java Util Logging support. With a special LTTngAgent located in > > > lttng-ust project (liblttng-ust-jul) to trace JUL events and gather > > > UST traces with them. > > > > > > The -j/--jul domain has been added to lttng command line so you can > > > list the possible JUL Logger object and enable/disable them. It is the > > > same as using the UST or Kernel domain. > > > > > > As of now, filters and loglevel are ignored with the JUL domain. > > > > Saying "It is the same as using the UST or Kernel domain" leaves a lot > > of questions unanswered, since the kernel and user-space behave *very* > > differently on a lot of points. > > > > 1) Does --jul require root privileges? > > No. JUL actually acts exactly like UST since it uses it thus a Java > application connect to the session daemon that it can talk to. > > > 2) I suppose the various commands have --kernel pre-empting --userspace > > pre-empting --ul? > > Yup. This is actually not mention anywhere but looking at "lttng" > command line code, the domain's order is: kernel, ust, jul. Probably we > should actually output an error if the user uses multiple domain... > > > 3) add-context: does --jul have the same possible context types as > > --userspace (i.e. ip, pthread_id, procname, vpid, vtid)? > > Nope. > > > 4) enable-channel: > > 4.1) Are the --jul --subbuf-size, --num-subbuf and --read-timer defaults > > the same as with --userspace? > > Nope. JUL uses it's internal channel so basically enable channel does > NOT support the jul domain thus not having -j in the help/man. > > > 4.2) Presumably --output can only be mmap? > > Yes. Same as UST but again you can't use enable-channel with JUl domain. > > > 4.3) Are the --jul buffering schemes the same as with --userspace (i.e. > > --buffers-pid and --buffers-uid)? > > Always per UID. You can't change it. > > > 4.4) If yes, won't they all degenerate to the virtual machine's user and > > process IDs? > > Not sure I understand this one? > > > 5) enable-event: > > 5.1) Can you assign --jul events to multiple channels like you can in > > --userspace? > > No. > > > 5.2) Is the --jul event type --tracepoint or something else entirely? > > It is tracepoint yes. For the JUL domain, ALL UST tracepoints are > enabled (there is only one for now with the lttng-ust library we use > (liblttng-ust-jul)). > > > 5.3) Can the trailing wild card (and exclusion option) be used in the event > > name when enabling/disabling --jul events? > > Wild card are NOT supported for the JUL domain. Thus for instance "lttng > enable-event -j my_event_subsystem42_*" will not work. Only the "*" will > work enabling every Loggers. > > > 6) list: Does bug #654 also apply to --jul? > > Yes most probably. The session name is ignored. > > > Now after answering all this, I feel like either creating a lttng-jul > man page or adding a special section in "lttng.1" for the JUL domain > explaining all this. Thoughts?
I guess adding a JUL domain section to lttng.1 might be the way to go. Otherwise, it's unclear that people will find the lttng-jul man page, given it is related to the "lttng" command. Thanks, Mathieu > > Cheers! > David > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
