DTrace Probes

FoundationDB contains many dtrace probes that can be inspected during runtime with tools like bcc and SystemTap. All of them are in the foundationdb provider namespace.

FDB_TRACE_PROBE is simply an alias to the varias DTRACE_PROBE macros.

Probes

Main-Loop

FDB_TRACE_PROBE(run_loop_begin)

Is called whenever the main network loop starts over.

FDB_TRACE_PROBE(run_loop_ready_timers, numTimers)

On each iteration of the run-loop, this indicates how many timers (created through delay or yield) are ready. Its argument is of type int.

FDB_TRACE_PROBE(run_loop_thread_ready, numReady)

On each loop-iteration. The second argument is of type int and it is the number of thread ready processes.

FDB_TRACE_PROBE(run_loop_yield)

Run loop yields.

FDB_TRACE_PROBE(run_loop_tasks_start, queueSize)

FDB_TRACE_PROBE(run_loop_done, queueSize)

One iteration of the run-loop is done. The argument is of type int and is the remaining number of tasks on the ready queue.