* Re: Difficulty extending existing tracepoint's reporting
[not found] <CAOxd4f5xL_OWh79s0kG0X9cFbgdkqZqzodnkOjVHwGndHOT75g@mail.gmail.com>
@ 2019-10-15 13:36 ` Jonathan Rajotte-Julien
0 siblings, 0 replies; 2+ messages in thread
From: Jonathan Rajotte-Julien @ 2019-10-15 13:36 UTC (permalink / raw)
To: David Boles; +Cc: lttng-dev
Hi David,
Did you add the lttng tracepoint definition in instrumentation/events/lttng-module/block.h
as it is done with block_rq_complete? (in lttng-modules source tree)
Cheers
--
Jonathan Rajotte-Julien
EfficiOS
^ permalink raw reply [flat|nested] 2+ messages in thread
* Difficulty extending existing tracepoint's reporting
@ 2019-10-14 21:23 David Boles
0 siblings, 0 replies; 2+ messages in thread
From: David Boles @ 2019-10-14 21:23 UTC (permalink / raw)
To: lttng-dev
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I am trying to widen the information reported by the block_rq_complete()
tracepoint, but am unable to get my extension to take affect. Basically,
I'd like 3 additional numbers captured at that point.
So far, I've failed to succeed in this effort. As part of trying to
determine what is going on, I've created a new tracepoint definition in
include/trace/event/block.h which defines block_rq_complete_ex, which is
just like block_rq_complete but with my additional fields. I've altered the
trace_block_rq_complete() call in block/blk-core.c to be
trace_block_rq_complete_ex().
Other than block_rq_complete being mentioned in blktrace.c (which *seems*
to be unrelated to the LTTng tracing), everywhere there is a mention of
block_rq_complete there is a matching mention of block_rq_complete_ex.
When I build a kernel (LTTng built in mode), the resulting kernel has
block_rq_complete_ex text in it. When I boot it, start an LTTng session,
and list the kernel tracepoints - my new tracepoint isn't listed. If I've
put a new printk in the kernel, it's output is visible. Any ideas on what
I'm missing? Things I've checked:
- Built from a distclean'd kernel tree
- lttng is "built in" (I ran the scripts/built_in.sh script and confirmed
the CONFIG_* flags
- I can enable the original block_rq_complete tracepoint and collect data
through it
- If instead of having a new tracepoint I just extend the old one, the new
data doesn't show up
It really seems like there is a cached or overriding definition of these
tracepoints that I'm getting instead of what I've compiled. There are
multiple kernels on the system, but I am booting the kernel I intend to.
Any ideas would be highly appreciated.
- db
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