----- On May 31, 2017, at 7:28 PM, Deneau, Tom [email protected] wrote: > I am using lttng 2.9.4. > > I have a server database daemon with many threads and I would like to track > events on a smaller subset of those threads. > I noticed that on the kernel channel I can use lttng track --pid=123,124,125 > > and this will trace kernel events for just those TIDS (in spite of the > documentation saying it will track whole pids). > But I am happy because tid tracking is what I want.
Argh.. this is an unfortunate discrepancy! It should have been using the kernel "tgid" at kernel-level to match what we do for userspace. I'll prepare a patch fixing that. LTTng really try hard to stick to "pid means process ID" and "tid means thread ID". Internally in lttng-modules we do all that is needed to map the pid/tgid notions back to tid/pid. > > However, is there an equivalent way to track certain tids on the userspace > channel? I find that if I use > lttng track -u --pid=xxx > it just tracks all the tids under that pid. You can use e.g. lttng enable-event -k -a --filter '$ctx.tid == 123' or if you want it container-aware: lttng enable-event -k -a --filter '$ctx.vtid == 123' Thanks, Mathieu > > Here is my script (where 79653 is a single tid). In this case it traces only > kernel events on that tid. > ----------- > lttng create > lttng enable-channel u -u --num-subbuf 64 --subbuf-size 512k > lttng enable-channel k -k --num-subbuf 64 --subbuf-size 512k > lttng add-context -k -c k -t tid -t pid > lttng add-context -u -c u -t vtid -t vpid > lttng enable-event -u -c u -a > lttng enable-event -k -c k --syscall futex > lttng track -k --pid=79653 > lttng track -u --pid=79653 > lttng start > sleep 1.0 > lttng stop > lttng destroy > > -- Tom Deneau > _______________________________________________ > lttng-dev mailing list > [email protected] > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
