LTTng » LTTng-tools

This was taken from a machine running 3.2.0-40-virtual:

$ lttng add-context --help 
usage: lttng add-context -t TYPE [-k|-u] [OPTIONS]
[...]
Context:
  -t, --type TYPE          Context type. You can repeat that option on
                           the command line to specify multiple contexts at once.
                           (--kernel preempts --userspace)
                           TYPE can be one of the strings below:
                               pid, procname, prio, nice, vpid, tid, pthread_id,
                               vtid, ppid, vppid, hostname, perf:cpu-cycles,
                               perf:cycles, perf:stalled-cycles-frontend,
                               perf:idle-cycles-frontend,
                               perf:stalled-cycles-backend,
                               perf:idle-cycles-backend, perf:instructions,
                               perf:cache-references, perf:cache-misses,
                               perf:branch-instructions, perf:branches,
                               perf:branch-misses, perf:bus-cycles,
                               perf:L1-dcache-loads, perf:L1-dcache-load-misses,
                               perf:L1-dcache-stores,
                               perf:L1-dcache-store-misses,
                               perf:L1-dcache-prefetches,
                               perf:L1-dcache-prefetch-misses,
                               perf:L1-icache-loads, perf:L1-icache-load-misses,
                               perf:L1-icache-stores,
                               perf:L1-icache-store-misses,
                               perf:L1-icache-prefetches,
                               perf:L1-icache-prefetch-misses, perf:LLC-loads,
                               perf:LLC-load-misses, perf:LLC-stores,
                               perf:LLC-store-misses, perf:LLC-prefetches,
                               perf:LLC-prefetch-misses, perf:dTLB-loads,
                               perf:dTLB-load-misses, perf:dTLB-stores,
                               perf:dTLB-store-misses, perf:dTLB-prefetches,
                               perf:dTLB-prefetch-misses, perf:iTLB-loads,
                               perf:iTLB-load-misses, perf:branch-loads,
                               perf:branch-load-misses, perf:cpu-clock,
                               perf:task-clock, perf:page-fault, perf:faults,
                               perf:major-faults, perf:minor-faults,
                               perf:context-switches, perf:cs,
                               perf:cpu-migrations, perf:migrations,
                               perf:alignment-faults, perf:emulation-faults
Example:
[...]
$ dmesg | grep "generic register" 
$ 

Trying to add-context -t perf:* on such a machine fails, of course.

It would be a simple yet useful enhancement to forgo listing perf context types when none are actually possible.