Let me advice you to benchmark it "accuracy" on your machine setup, don't rely what is on that page.
Make sure the error with --jit-verbose=1 which will show whether it uses MJIT correctly.
ruby --jit-verbose=1
- N-Body single core
Ruby 2.6.3 6:22.00s
RubyJIT 2.6.3 3:58.18s
PHP 7.3.xx 4:10.90s
…
JIT success (511.7ms): [email protected]:14 -> /tmp/_ruby_mjit_p5804u105.c
JIT success (397.5ms): block in [email protected]:68 -> /tmp/_ruby_mjit_p5804u106.c
JIT success (607.0ms): block in [email protected]:50 -> /tmp/_ruby_mjit_p5804u108.c
JIT compaction (53.6ms): Compacted 111 methods -> /tmp/_ruby_mjit_p5804u111.so
Successful MJIT finish
real 6m4.201s
user 6m42.813s
sys 0m4.041s
$ time /opt/src/php-7.3.11/bin/php -n nbody.php 50000000
-0.169075164
-0.169059907
real 5m24.915s
user 5m24.808s
sys 0m0.020ruby 2.7.0dev (2019-11-23T07:06:30Z master b563439274) [x86_64-darwin18]
gtime -v /usr/local/bin/ruby --jit -W0 nbody.rb 50000000 -0.169075164 -0.169059907
Command being timed: "/usr/local/bin/ruby --jit -W0 nbody.rb 50000000"
User time (seconds): 249.30 System time (seconds): 0.58 Percent of CPU this job got: 100% Elapsed (wall clock) time (h:mm:ss or m:ss): 4:08.97
---
PHP 7.3.11 (cli) (built: Oct 24 2019 11:29:52) ( NTS ) Copyright (c) 1997-2018 The PHP Group Zend Engine v3.3.11, Copyright (c) 1998-2018 Zend Technologies with Zend OPcache v7.3.11, Copyright (c) 1999-2018, by Zend Technologies
gtime -v php -n nbody.php 50000000
-0.169075164 -0.169059907
Command being timed: "php -n nbody.php 50000000" User time (seconds): 248.02 System time (seconds): 0.49 Percent of CPU this job got: 99% Elapsed (wall clock) time (h:mm:ss or m:ss): 4:09.82