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SubjectRe: [ANNOUNCE] New tools: lttngtrace and lttngreport

* Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:

> Well, I'm afraid the collection approach "trace" is currently taking won't allow
> this kind of dependency wakeup chain tracking, because they focus on tracing
> operations happening on a thread and its children, but the reality is that the
> wakeup chains often spread outside of this scope.
>
> This is why lttngtrace gathers a system-wide trace even though we're mostly
> intested in the wait/wakeups of a specific PID.

Mathieu, what you say is factually wrong - of course perf events allows system-wide
tracing, it always did.

This is available in the 'trace' tool as well, try:

$ trace record --all sleep 1 # do system-wide tracing

# trace recorded [1.928 MB] - try 'trace summary' to get an overview

$ trace summary

.-----------------------------------.
__) Summary of 'sleep 1' events (__

[ task - pid ] [ events ] [ ratio ] [ runtime ]
_____________________________________________________________________

swapper - 0 : 64 [ 0.4% ] 0.000 ms
ksoftirqd/0 - 3 : 6 [ 0.0% ] 0.063 ms
migration/1 - 7 : 2 [ 0.0% ] 0.000 ms
kworker/0:1 - 10 : 6 [ 0.0% ] 0.139 ms
kworker/6:1 - 53 : 3 [ 0.0% ] 0.014 ms
kworker/5:1 - 54 : 3 [ 0.0% ] 0.014 ms
kworker/4:1 - 55 : 3 [ 0.0% ] 0.014 ms
kworker/3:1 - 56 : 3 [ 0.0% ] 0.015 ms
kworker/2:1 - 57 : 3 [ 0.0% ] 0.015 ms
kworker/1:1 - 58 : 3 [ 0.0% ] 0.015 ms
kworker/15:1 - 318 : 6 [ 0.0% ] 0.045 ms
kworker/14:1 - 319 : 6 [ 0.0% ] 0.033 ms
kworker/13:1 - 320 : 6 [ 0.0% ] 0.036 ms
kworker/12:1 - 321 : 6 [ 0.0% ] 0.035 ms
kworker/11:1 - 322 : 6 [ 0.0% ] 0.041 ms
kworker/10:1 - 323 : 6 [ 0.0% ] 0.037 ms
kworker/9:1 - 324 : 6 [ 0.0% ] 0.042 ms
kworker/7:1 - 326 : 6 [ 0.0% ] 0.032 ms
kworker/8:2 - 1047 : 6 [ 0.0% ] 0.039 ms
sendmail - 2327 : 18 [ 0.1% ] 0.111 ms
trace - 32281 : 15728 [ 96.2% ] 86.478 ms
sleep - 32282 : 460 [ 2.8% ] 1.305 ms
_____________________________________________________________________

As you can see all those kworker events - it's a system-wide trace.

This is in addition to per process and per workflow (child hierarchy) tracing -
which we expect to be more commonly used.

Thanks,

Ingo


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