Adding date and time to log entries will help to investigate bugs during development and issues in production.

Getting time and putting it in a human-readable format is not a cheap operation, so the implementation must only do it when a log entry is logged. A solution to delay getting the time just before logging is to add the field char str_date_time[32]; to struct log_ratelimit_state, and pass this field to rte_log_ratelimit() at macro G_LOG(). Thus, rte_log_ratelimit() can update the field str_date_time before calling rte_vlog(). This change requires adding the time string to the define G_LOG_PREFIX, which, in turn, requires adjusting log_ratelimit_reset().

The string format of the time added to log entries should be the same format used in log_stats(). Once time is being added to all log entries, log_stats() must no longer add time on its own.

To further reduce the number of times that time is obtained, one can add the field uint64_t update_time_at, so the field str_date_time is only updated once one second has passed. One should update the field uint64_t update_time_at with rte_rdtsc(). Replacing time(2) with clock_gettime(2) gives the time needed for logging and how much time is left until the next second in nanoseconds.