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Back to the drawing board for utrace?

Back to the drawing board for utrace?

Posted Jan 31, 2010 7:59 UTC (Sun) by sfink (guest, #6405)
Parent article: Back to the drawing board for utrace?

Speaking as just a dumb userspace developer:

Man, am I confused! I have a relatively straightforward problem: I am trying to track down
latency and jitter problems in a realtime media stream generating application. How do I
decide what tool to use? Oprofile? Ftrace? Perf events? SystemTap? LTTng?

I've tried oprofile briefly, and it seemed mostly irrelevant for my problems. I can't find any
clear descriptions of what ftrace and perf events actually are, so that I could figure out
whether I should bother with them. I've been fairly happy with systemtap so far -- it is at least
straightforward to dive into and start generating customized traces that at least startto
address what I'm interested in. Each further step seems to involve more and more groveling
about in the kernel sources, but at least I can understand the path ahead and predict what's
going to be possible. (I have a fairly generic problem -- I want to measure the jitter between
context switches of my realtime threads and then diagnose the reasons for that jitter by
reporting what the CPUs were up to when I wasn't running.)

But now I see that SystemTap is viewed as the bastard stepchild, and I wonder if my
investment into learning to use SystemTap was an expensive mistake. Any guidance on
choosing an appropriate tool for unfortunates like me?


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Back to the drawing board for utrace?

Posted Feb 1, 2010 11:59 UTC (Mon) by fuhchee (guest, #40059) [Link]

"But now I see that SystemTap is viewed as the bastard stepchild"

Heh. But the passive voice gives the opinion false authority.

"and I wonder if my investment into learning to use SystemTap was an expensive mistake."

You should explore the alternatives and use whatever works for you.
Listening to simple smears may well be self-defeating.

Back to the drawing board for utrace?

Posted Feb 1, 2010 13:36 UTC (Mon) by Cyberax (✭ supporter ✭, #52523) [Link]

WHICH ONE???

I'm in the same WTF situation. There are like 6 "tracing" solutions for Linux. Most of them with only a few lines of documentation (SystemTap at least is the most documented of them).

That's a complete SNAFU. Why can't we have one nice user-oriented solution?

SystemTap documentation

Posted Feb 1, 2010 14:29 UTC (Mon) by mjw (subscriber, #16740) [Link]

Yes, choice is such a drag. But none of them will go away soon. Especially not SystemTap which has always had a pretty loyal following and dedicated developers to make it work with whatever the kernel provides. Ultimately they will just share more and more features and they will all become more or less frontends to the same backend kernel features. Something like utrace and uprobes will ultimately get supported in the kernel and then the other tools will also get better user space tracking.

The SystemTap documentation can be found at:
http://sourceware.org/systemtap/SystemTap_Beginners_Guide/
http://sourceware.org/systemtap/langref/
http://sourceware.org/systemtap/examples/


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