On 2014-11-10 07:19, Vasily Tarasov wrote:
Hi Jens, td->start is used in __show_running_run_stats() to compute the time that passed since the beginning of the loop (stored in td->start) to the moment when periodical statistics need to be printed. Then td->ts.runtime[] is temporarily updated based on the computed value. In thread_main(), similar actions are taken to update td->ts.runtime[] based on the td->start and the loop's elapsed time. Without the patch, td->start is set in the very beginning of the loop in thread_main(). So, it leaves a time window between the end of the current loop and the beginning of the next loop when td->ts.runtime[] is already updated while td->start still stores the start of the previous lop. If __show_running_run_stats() is called during that window - the time can be (temporarily) added twice to td->ts.runtime[]. However, if we reset the start time in the end of the loop under the stat_mutex it should not happen. I would agree that having a per-td mutex might be an overkill considering that people usually print statistics periodically with relatively long intervals: 1, 5, 10, 60 seconds.
Thanks, I missed the change in addition after IO was done, hence the question on ->start. I did commit the patch as-is yesterday, thanks!
-- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
