On 8/29/24 02:06, Jens Axboe wrote: > On 8/27/24 1:08 AM, Shin'ichiro Kawasaki wrote: >> When write_lat_log option is set, fio outputs the 'clat' completion >> latency log file. This clat log can be used to analyze IO latency. This >> file can also be considered as an IO trace file as each IO entry can >> fully describe an IO when the --log_offset and --log_prio options are >> also used. However, using the clat log file as an IO trace is inaccurate >> because the time field of each entry uses millisecond units, which is >> too coarse for fast IOs (e.g. when using SSDs). This series proposes the >> new option 'log_issue_time' to address the inaccuracy problem. When this >> option is set, fio adds another field to the log file entries to log an >> IO issuing time in nanoseconds. >> >> The first four patches in the series clean up the current code as >> preparation. The 5th patch introduces the 'log_issue_time' option. The >> following two patches document the new option. The last two patches add >> two test cases to check the log file format. > > In general this looks fine, and I think it's a useful feature. However, > should we have an option to make the generic time in the log entry be > in nsec as well? I am not sure if it is that useful given that the entry time field does not directly correspond to any I/O time. But to be consistent with the other time fields, I may be good to add this option. That is easy to do. -- Damien Le Moal Western Digital Research
