$ docker run --rm -it jruby:9-alpine jruby -v
jruby 9.1.16.0 (2.3.3) 2018-02-21 8f3f95a OpenJDK 64-Bit Server VM 25.151-b12 on 1.8.0_151-b12 +jit [linux-x86_64]

$ docker run --rm -it jruby:9-alpine jruby '-Xjit?'
jit.threshold=50
jit.max=4096
jit.maxsize=2000
jit.logging=false
jit.logging.verbose=false
jit.dumping=false
jit.logEvery=0
jit.exclude=
jit.debug=false
jit.background=true
jit.kernel=false
ir.jit.passes=null
jit.cache=true
jit.codeCache=null

$ docker run --rm -it jruby:9-alpine jruby -Xjit.max=16384 | head
expr: syntax error
jruby: invalid extended option jit.max=16384 (-X will list valid options)

Usage: jruby [switches] [--] [programfile] [arguments]
  -0[octal]         specify record separator (\0, if no argument)
  -a                autosplit mode with -n or -p (splits $_ into $F)
  -c                check syntax only
  -Cdirectory       cd to directory, before executing your script
  -d                set debugging flags (set $DEBUG to true)
  -e 'command'      one line of script. Several -e's allowed. Omit [programfile]

$ docker run --rm -it jruby:9-alpine jruby -Xjit.logging=true | head
expr: syntax error
jruby: invalid extended option jit.logging=true (-X will list valid options)

Usage: jruby [switches] [--] [programfile] [arguments]
  -0[octal]         specify record separator (\0, if no argument)
  -a                autosplit mode with -n or -p (splits $_ into $F)
  -c                check syntax only
  -Cdirectory       cd to directory, before executing your script
  -d                set debugging flags (set $DEBUG to true)
  -e 'command'      one line of script. Several -e's allowed. Omit [programfile]