RFR: 8246436: JFR: Avoid parsing metadata.xml during startup

[Erik Gahlin]

Thanks for all the reviews and the measurements!

Erik

> On 18 Jun 2020, at 13:56, Claes Redestad <claes.redestad at oracle.com> wrote:
> 
> Hi Erik,
> 
> looks good - and a great improvement!
> 
> By my measures this removes about 12% of the total JVM cpu use when
> running a Hello World with -XX:StartFlightRecording - or roughly 35ms
> off the total runtime[1]
> 
> /Claes
> 
> [1]
> perf stat -r 25 java -XX:StartFlightRecording HelloWorld
> 
> Before:
>       2622.928325      task-clock (msec)         #    5.092 CPUs utilized            ( +-  1.13% )
>             6,654      context-switches          #    0.003 M/sec               ( +-  2.36% )
>                30      cpu-migrations            #    0.012 K/sec               ( +-  5.10% )
>            29,573      page-faults               #    0.011 M/sec               ( +-  1.40% )
>     5,952,854,795      cycles                    #    2.270 GHz               ( +-  1.10% )
>     6,431,402,332      instructions              #    1.08  insn per cycle           ( +-  0.87% )
>     1,285,805,882      branches                  #  490.218 M/sec               ( +-  0.87% )
>        50,742,706      branch-misses             #    3.95% of all branches          ( +-  0.81% )
> 
>       0.515076132 seconds time elapsed          ( +-  1.41% )
> 
> After:
>       2300.679150      task-clock (msec)         #    4.778 CPUs utilized            ( +-  1.28% )
>             6,509      context-switches          #    0.003 M/sec               ( +-  2.19% )
>                29      cpu-migrations            #    0.012 K/sec               ( +-  5.23% )
>            28,050      page-faults               #    0.012 M/sec               ( +-  1.78% )
>     5,177,014,775      cycles                    #    2.250 GHz               ( +-  1.32% )
>     5,573,218,149      instructions              #    1.08  insn per cycle           ( +-  1.07% )
>     1,116,169,965      branches                  #  485.148 M/sec               ( +-  1.08% )
>        44,986,319      branch-misses             #    4.03% of all branches          ( +-  0.85% )
> 
>       0.481467615 seconds time elapsed          ( +-  1.27% )
> 
> 
> On 2020-06-18 01:16, Erik Gahlin wrote:
>> Hi,
>> Could I have review of an enhancement that will avoid parsing the XML metadata for the JVM events during startup/runtime.
>> Thanks to Magnus for helping out with changes to the make files.
>> Bug:
>> https://bugs.openjdk.java.net/browse/JDK-8246436
>> Webrev:
>> http://cr.openjdk.java.net/~egahlin/8246436/
>> Testing: tier1+tier2 + jdk/jdk/jfr
>> Thanks
>> Erik