Hello Bala,
If you'd like more information about which event types (tracepoints) are
practical for investigating which areas, the `ltting-utils` [1] project
could be useful! The repository contains scripts that record LTTng
traces. Each script is focused on a different investigation area (e.g.
network, interrupts, disk, etc).
You could use the scripts themselves and/or read the `*.profile` files
[2] to see the event types enabled by the different profiles. For
example, in the disk analysis profile (disk.profile), the following
event types are enabled:
- block_rq_complete
- block_rq_insert
- block_rq_issue
- block_bio_frontmerge
As Millian suggested, it is often best to only trace the event types you
need for the type of issue you are investigating since this increases
the accuracy of the data collected (less tracing overhead, fewer dropped
events) and also makes the trace easier to understand (less data volume,
less data noise).
Best,
Erica
----
LINKS
[1] lttng-utils: https://github.com/tahini/lttng-utils/tree/master
[2] Tracing Profiles:
https://github.com/tahini/lttng-utils/tree/master/lttngutils/profiles
On 2023-08-15 01:24, Milian Wolff via lttng-dev wrote:
On Sonntag, 13. August 2023 16:58:17 CEST Bala Gundeboina via lttng-dev wrote:
Hi,
I am Using LTTng in my project , I am recording a kernel session for long
duration (eg more than 15minutes) I am enabling all the events for
recording but some events discarding after stopping the session, if i run
more than 5 minutes only some events are discarding. I have tried to change
in the .ltttngrc file also to increase buffer-size.
While not directly related to your question, I strongly encourage you to
review the list of events and only enable those that are actually required for
the specific issue you are investigating. Some kernel events are _extremely_
high frequency but have often no practical use for many (at least in my
experience and for my own purposes). Examples for the latter are esp. the
kmalloc tracepoints.
lttng destroy
Destroying session `my-kernel-session`...
Session `my-kernel-session` destroyed
Warning: 94424667 events were discarded, please refer to the documentation
on channel configuration
actually when i am running below command i am getting below warning i am
thinking this is the issue because sometimes this warning is not coming
that i didn't seen discarded events. how to overcome this problem can you
provide some detailed lttng-sessiond --daemonize
Warning: Failed to produce a random seed using getrandom(), falling back to
pseudo-random device seed generation which will block until its pool is
initialized: Failed to get true random data using getre
Thanks & Regards
Bala Gundeboina
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