PHPC-2337 fixed an issue where I inadvertently forgot to explicitly disable tracing at runtime (PHPC compiles with tracing enabled, so that was the default), despite clearing libmongoc's log handler. This introduced a performance regression whereby trace log messages were still generated, but never written.

A possible improvement in libmongoc would have mongoc_log_trace_iovec() and mongoc_log_trace_bytes() return early if a log handler isn't registered (beyond just checking whether tracing is enabled). mongoc_log() already does this itself for its stop_logging calculation.

One approach may be to turn the following snippet from mongoc_log() into a macro to call from all three functions:

stop_logging = !gLogFunc;
stop_logging = stop_logging || (log_level == MONGOC_LOG_LEVEL_TRACE &&
                                !_mongoc_log_trace_is_enabled ());
if (stop_logging) {
   return;
}