RFR (S): Percentile levels in -Xlog:gc+stats

[Roman Kennke]

Am Montag, den 09.01.2017, 12:56 +0100 schrieb Aleksey Shipilev:
> On 01/09/2017 11:48 AM, Roman Kennke wrote:
> > Maybe instead of multiplying by 1000, measure more precisely?
> 
> We are measuring precisely: the counters reply in floating-point
> seconds, so
> multiplying to 1K or 1M gives you integral milliseconds and
> microseconds,
> respectively. HDR storage would coarsen, though, to get footprint
> advantages.

I was suspicious about those numbers:

  Concurrent Marking Times   = 1.80 s (avg =   179735 us)
    (num =    10, lvls (10% step, us) =
       174000, 176000, 176000, 176000, 177000, 180000, 180000, 181000,
...



> > Can't we have both max/SD and percentile stats? Or does it not make
> > sense at all to see max/sd?
> 
> SD is useless for non-normal distributions. Well, average is
> misleading too,
> unless levels say the distribution looks uniform/normal enough. The
> last level
> was supposed to be maximum, but it might be not evident from the
> logging.
> Changed it to explicit "max":
> 
>   Concurrent Marking Times   =    15.24 s (avg =    64594 us)
>     (num =   236, lvls (10% step, us) =
>        273, 463, 609, 863, 1055, 1895, 185547, 199219, 199219, max =
> 204852)
> 
> Is this better? Ok to push?

OK.

Roman