Re: [PATCH 0/9] introduce the log_issue_time option

[Jens Axboe <axboe@kernel.dk>]

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?

-- 
Jens Axboe