LTTng » LTTng-tools

I recently tried remembering how to filter by cpu_id when enabling an event, and found that there was not clear way to see that $ctx.cpu_id actually exists from the lttng man pages (other than a random example in the lttng-enable-event man page). AFAIU the man pages rely on lttng add-context --list to let the user discover the available contexts. This is likely because the cpu_id context is not available for the "add-context" command because it would be redundant with the implicit context already sampled with the buffers.

We may want to have some way to let users discovers those contexts which are filter-specific.

My use-case is to try to grab only traces for a few logical cpus (0-3) from my 384 logical cpus machine.