From mboxrd@z Thu Jan 1 00:00:00 1970 From: dgoulet@efficios.com (David Goulet) Date: Tue, 4 Feb 2014 14:13:17 -0500 Subject: [lttng-dev] Questions about JUL (was: Re: lttng-dev Digest, Vol 67, Issue 48) In-Reply-To: <48CF5AC71E61DB46B70D0F388054EFFD267DE218@VAL-E-02.valcartier.drdc-rddc.gc.ca> References: <48CF5AC71E61DB46B70D0F388054EFFD267DE218@VAL-E-02.valcartier.drdc-rddc.gc.ca> Message-ID: <20140204191317.GF13440@thessa> On 04 Feb (18:59:02), Thibault, Daniel wrote: > ---------------------------------------------------------------------- > Date: Tue, 4 Feb 2014 12:17:36 -0500 > From: David Goulet > To: Jim Dumont > Cc: "lttng-dev at lists.lttng.org" > > >> 3) add-context: does --jul have the same possible context types as --userspace (i.e. ip, pthread_id, procname, vpid, vtid)? > > > > Nope. > > What are the possible context types then? Or is it just that you can't apply a filter to a jul event? None, you can't add a context to the JUL domain. > > >> 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. > > So you turn jul events on and off using enable/disable-event --all instead? This is getting a tad confusing: jul events force you to use only enable/disable-event but kernel syscalls force you to use only enable/disable-channel... No. For JUL you enable "Logger" names from the JUL API. For instance: $ lttng enable-event -j MyLogger or to enable all loggers $ lttng enable-event -j -a Using the lttng-ctl API, -a == "*". For the kernel syscalls, yeah well this is a tracer limitation that we can't enable/disable specific syscalls but fortunately this year we'll bring this feature! :) > > >> 4.4) If yes, won't they all degenerate to the virtual machine's user and process IDs? > > > > Not sure I understand this one? > > A Java application is interpreted and runs in a Java virtual machine (JVM). The userID and processID of any jul events are thus likely to be those of the JVM process. I would expect Java apps launched by separate users to launch separate JVM instances, but I would also expect two separate Java apps launched by the same user to share a single JVM (the user's) and, therefore, their process IDs. This could get fun with multi-threaded Java apps. Hrm, I've not observed that. If a specific Linux user with let say UID = 1000, the Java application registering to the session deamon is set with UID = 1000. Don't forget that the JUL support uses JNI to link with lttng-ust and that library registers as a the user. > > > 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? > > We definitely need an additional section in "lttng.1". Agreed. I'll be updating lttng.1 before the stable release. THanks! David > > Daniel U. Thibault > Protection des syst?mes et contremesures (PSC) | Systems Protection & Countermeasures (SPC) > Cyber s?curit? pour les missions essentielles (CME) | Mission Critical Cyber Security (MCCS) > R & D pour la d?fense Canada - Valcartier (RDDC Valcartier) | Defence R&D Canada - Valcartier (DRDC Valcartier) > 2459 route de la Bravoure > Qu?bec QC G3J 1X5 > CANADA > Vox : (418) 844-4000 x4245 > Fax : (418) 844-4538 > NAC : 918V QSDJ > Gouvernement du Canada | Government of Canada > > > _______________________________________________ > lttng-dev mailing list > lttng-dev at lists.lttng.org > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 603 bytes Desc: Digital signature URL: