RFR: 8232594: Make the output of the JFR command duration more user friendly

[Erik Gahlin]

Hi Chihiro,

Markus and I discussed what would be a suitable format and this is what 
we came up with:

- A duration of 0 is displayed as "0 s"
- A duration less than 1 second is displayed in ms with 3 significant 
digits.
- A duration between 1 second and 60 seconds is displayed in s with 
three significant units
- A duration of 60 second or more uses a combination of two units, for 
example "1 m 30 s" or "3 h 30 m"
- The maxmim unit is a day.

I wrote a unit tests that you can use. Hopefully it is correct.

http://cr.openjdk.java.net/~egahlin/8232594/

Thanks
Erik

On 2019-10-31 15:47, Chihiro Ito wrote:

> Hi Erik,
>
> I can't imagine one event lasting more than a day.
> Therefore, I think the number of days is unnecessary.
> I also think we don't need duration as detailed as ns.
>
> So how about using 0.001 ms to hours?
>
> Also, it would be difficult to see all the units displayed.
> About rounding, how about using up to 3 units?
>
> For example:
> 27 h 34 m 56 s
> 34 m 56 s 789 ms
> 56 s 789.012 ms
> 789.012 ms
>
> Regards,
> Chihiro
>
>
> 2019年10月30日(水) 2:57 Erik Gahlin <erik.gahlin at oracle.com 
> <mailto:erik.gahlin at oracle.com>>:
>
>     Hi Chihiro,
>
>     I don't think 1 day is a good representation of for example 27 hours.
>     The precision is too low.  I also think numbers should be rounded up
>     where applicable.
>
>     When a duration is short, it is often convenient to use ms (with some
>     fractions) instead of microseconds. It makes it easier to compare
>     values. This is especially true if you are looking at multiple values
>     and want to compare them, for example GC pause time.
>
>     It is probably a good idea to first decide how values should be
>     formatted before attempting an implementation.
>
>     Erik
>
>     > Hi,
>     >
>     > I tried to implement this to output an accurate time duration.
>     > Could you review this, please?
>     >
>     > Is a rounded duration better than an exact duration?
>     >
>     > JBS https://bugs.openjdk.java.net/browse/JDK-8232594
>     > webrev http://cr.openjdk.java.net/~cito/JDK-8232594/webrev.00/
>     >
>     > Regards,
>     > Chihiro
>