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

[Claes Redestad]

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
>