Add a new system config 'enable_jit'

This adds a new option to enable Ruby JIT in worker processes.

The exact JIT strategy (in particular mjit or yjit) will be chosen
by Ruby as it sees fit. See the following ticket for details:

    https://bugs.ruby-lang.org/issues/18349

Signed-off-by: Fujimoto Seiji <fujimoto@ceptord.net>

lib/fluent/supervisor.rb

@@ -1104,6 +1104,11 @@ def build_spawn_command
         fluentd_spawn_cmd << '-Eascii-8bit:ascii-8bit'
       end
 
+      if @system_config.enable_jit
+        $log.info "enable Ruby JIT for workers (--jit)"
+        fluentd_spawn_cmd << '--jit'
+      end
+
       # Adding `-h` so that it can avoid ruby's command blocking
       # e.g. `ruby -Eascii-8bit:ascii-8bit` will block. but `ruby -Eascii-8bit:ascii-8bit -h` won't.
       _, e, s = Open3.capture3(*fluentd_spawn_cmd, "-h")

lib/fluent/system_config.rb

@@ -28,7 +28,7 @@ class SystemConfig
       :without_source, :rpc_endpoint, :enable_get_dump, :process_name,
       :file_permission, :dir_permission, :counter_server, :counter_client,
       :strict_config_value, :enable_msgpack_time_support, :disable_shared_socket,
-      :metrics, :enable_input_metrics, :enable_size_metrics
+      :metrics, :enable_input_metrics, :enable_size_metrics, :enable_jit
     ]
 
     config_param :workers,   :integer, default: 1
@@ -50,6 +50,7 @@ class SystemConfig
     config_param :disable_shared_socket, :bool, default: nil
     config_param :enable_input_metrics, :bool, default: nil
     config_param :enable_size_metrics, :bool, default: nil
+    config_param :enable_jit, :bool, default: false
     config_param :file_permission, default: nil do |v|
       v.to_i(8)
     end

test/config/test_system_config.rb

@@ -84,6 +84,7 @@ def parse_text(text)
       assert_nil(sc.enable_input_metrics)
       assert_nil(sc.enable_size_metrics)
       assert_nil(sc.enable_msgpack_time_support)
+      assert(!sc.enable_jit)
       assert_equal(:text, sc.log.format)
       assert_equal('%Y-%m-%d %H:%M:%S %z', sc.log.time_format)
     end
@@ -102,6 +103,7 @@ def parse_text(text)
       'enable_msgpack_time_support' => ['enable_msgpack_time_support', true],
       'enable_input_metrics' => ['enable_input_metrics', true],
       'enable_size_metrics' => ['enable_size_metrics', true],
+      'enable_jit' => ['enable_jit', true],
     )
     test "accepts parameters" do |(k, v)|
       conf = parse_text(<<-EOS)