[lttng-dev] [RELEASE] LTTng-Tools 2.4.0-rc1 - Époque Opaque

[Thibault, Daniel]

-----Message d'origine-----
Date: Fri, 15 Nov 2013 12:27:01 -0500
From: David Goulet <dgoulet at efficios.com>

> 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?

> 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?
2) I suppose the various commands have --kernel pre-empting --userspace pre-empting --ul?
3) add-context: does --jul have the same possible context types as --userspace (i.e. ip, pthread_id, procname, vpid, vtid)?
4) enable-channel:
4.1) Are the --jul --subbuf-size, --num-subbuf and --read-timer defaults the same as with --userspace?
4.2) Presumably --output can only be mmap?
4.3) Are the --jul buffering schemes the same as with --userspace (i.e. --buffers-pid and --buffers-uid)?
4.4) If yes, won't they all degenerate to the virtual machine's user and process IDs?
5) enable-event:
5.1) Can you assign --jul events to multiple channels like you can in --userspace?
5.2) Is the --jul event type --tracepoint or something else entirely?
5.3) Can the trailing wild card (and exclusion option) be used in the event name when enabling/disabling --jul events?
6) list: Does bug #654 also apply to --jul?

Daniel U. Thibault
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