$ java -XX:StartFlightRecording:filename=probe.jfr --sun-misc-unsafe-memory-access=allow -cp build Probe     (silent: no warnings)
got Unsafe instance
read back 42
allocate/put/get/free all succeeded
second use read 7
$ jfr print --events jdk.DeprecatedInvocation probe.jfr | grep -E 'method = |line:' | sort | uniq -c
  1 Probe.main(String[]) line: 12
  1 Probe.main(String[]) line: 13
  1 Probe.main(String[]) line: 14
  1 Probe.main(String[]) line: 15
  1 method = sun.misc.Unsafe.allocateMemory(long)
  1 method = sun.misc.Unsafe.freeMemory(long)
  1 method = sun.misc.Unsafe.getLong(long)
  1 method = sun.misc.Unsafe.putLong(long, long)