On 2023-08-23 13:14, Matthew Khouzam via lttng-dev wrote:
Here is a youtube video showing how userspace and kernel traces can play
nicely together.
https://www.youtube.com/watch?v=K1JNQ-HkC6w
------------------------------------------------------------------------
*From:* lttng-dev <lttng-dev-boun...@lists.lttng.org> on behalf of Bala
Gundeboina via lttng-dev <lttng-dev@lists.lttng.org>
*Sent:* Wednesday, August 23, 2023 2:17 AM
*To:* lttng-dev@lists.lttng.org <lttng-dev@lists.lttng.org>
*Subject:* [lttng-dev] userspace logs cpu analysis and LTTng UST Callstack
Hi all,
I have capturing kernel and userspace trace logs with LTTng
but kernel logs will give more useful information but userspace logs is
not giving more useful information compared to kernel trace logs, how to
get the more data from userspace trace logs. PFA of userspace and kernel
screenshots if you observe the kernel screenshot we will get per core
cpu usage, thread analysis and more .
Hello Bala,
I'm not sure exactly what you mean by, "userspace logs is not giving
more useful information compared to kernel trace logs", but I would
guess you mean: when reading the _userspace trace by itself_ in Trace
Compass, there are way fewer visualisations available compared to when
you view the _kernel trace by itself_ in Trace Compass.
It can be normal for a kernal trace to provide much more data than a
userspace trace. Each visualisation in Trace Compass requires certain
kinds of data (event types). The amount of events in a trace is a
function of the number of tracepoints (the number of instrumented
locations) in the code that are available and enabled. The kernel has a
very large number of tracepoints that already come with the code. On the
other hand, userspace applications often need to have the tracepoints
added manually by the folks interested in tracing it. This means that
userspace traces could have fewer events (if there are fewer available
tracepoints).
One purpose of a userspace trace is to provide context for a kernel
trace. To get the most information, you would capture both a kernel and
userspace trace simultaneously and then view the traces together as a
combined trace (rather that viewing them separately). When viewing the
userspace and kernel information together you get the volume and
richness of kernel information combined with the more "human-readable"
abstract information from userspace that makes the kernel information
easier to navigate.
As Matthew mentioned, the tool Trace Compass allows you to open the
kernel and userspace traces together as a combined trace. Trace Compass
uses the term "Experiment" to refer to a set of traces viewed together
on a single timeline, but in practice this is a combined trace. To get
the full analytical power of the kernel and userspace traces I would
recommend creating a Trace Compass Experiment with the kernel and
userspace traces. The video Matthew shared gives you information about
how to combine and view the traces using an Experiment (see resources
section below).
In the resources section below, I also included a link to a set of
tracing analysis examples. I haven't checked, but there may be an
example there that shows how to create a combined trace (Trace Compass
Experiment). The Trace Compass user interface has likely changed since
the screenshots were taken so you may not be able to follow the guide
word-for-word, but I think it may still serve as a useful reference.
Best regards,
Erica
----
RESOURCES
- Creating a combined kernel and userspace trace using a Trace Compass
Experiment (via Matthew Khouzam):
https://www.youtube.com/watch?v=K1JNQ-HkC6w
(A method of trace Experiment creation is shown starting at 0:58)
- Trace viz labs: Analyze a kernel trace in Trace Compass
https://github.com/dorsal-lab/Tracevizlab/tree/master/labs/101-analyze-system-trace-in-tracecompass
- All Trace viz labs:
https://github.com/dorsal-lab/Tracevizlab/tree/master/labs
i am not able to load userspace trace logs in tracealyzer ,is
tracealyzer is not supported the userspace logs ? , is there anyway we
can make enable it ? kindly please me to sort out of this problem.
I'm not familiar with Tracealyzer so I'm not sure about its
compatibility with these traces. I would suggest you reach out to the
Tracealyzer folks to ask about compatibility with their tools.
Tracealyzer is a proprietary tool and my understanding is that on this
mailing list we prefer to focus on free and open-source tools when
possible (since information about them can be more widely used).
Thanks
Bala Gundeboina
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