Set realtime priorities if available

This significantly reduces the latency with no real drawbacks from what
I've noticed. Wineserver is still run using the normal scheduling
policies because from my testing running that with realtime priority
that can actually increase latencies, although doing so will greatly
reduce the variance in processing time.

src/plugin/plugin-bridge.cpp

@@ -16,12 +16,13 @@
 
 #include "plugin-bridge.h"
 
-// Generated inside of build directory
+// Generated inside of the build directory
 #include <src/common/config/config.h>
 #include <src/common/config/version.h>
 
 #include "../common/communication.h"
 #include "../common/events.h"
+#include "../common/utils.h"
 #include "utils.h"
 
 namespace bp = boost::process;
@@ -78,6 +79,7 @@ PluginBridge::PluginBridge(audioMasterCallback host_callback)
                                                      logger,
                                                      vst_plugin_path,
                                                      socket_endpoint.path()))),
+      has_realtime_priority(set_realtime_priority()),
       wine_io_handler([&]() { io_context.run(); }) {
     log_init_message();
 
@@ -598,6 +600,8 @@ void PluginBridge::log_init_message() {
              << std::endl;
     init_msg << "plugin:       '" << vst_plugin_path.string() << "'"
              << std::endl;
+    init_msg << "realtime:     '" << (has_realtime_priority ? "yes" : "no")
+             << "'" << std::endl;
     init_msg << "socket:       '" << socket_endpoint.path() << "'" << std::endl;
     init_msg << "wine prefix:  '";
 

src/plugin/plugin-bridge.h

@@ -183,6 +183,14 @@ class PluginBridge {
      * @see launch_vst_host
      */
     std::unique_ptr<HostProcess> vst_host;
+
+    /**
+     * Whether this process runs with realtime priority. We'll set this _after_
+     * spawning the Wine process because from my testing running wineserver with
+     * realtime priority can actually increase latency.
+     */
+    bool has_realtime_priority;
+
     /**
      * Runs the Boost.Asio `io_context` thread for logging the Wine process
      * STDOUT and STDERR messages.

src/plugin/utils.cpp

@@ -25,7 +25,7 @@
 #include <random>
 #include <sstream>
 
-// Generated inside of build directory
+// Generated inside of the build directory
 #include <src/common/config/config.h>
 
 #include "../common/configuration.h"