From ab8d1c02d47e4f20d170ebde6d02994566a1357b Mon Sep 17 00:00:00 2001
From: elsid <elsid.mail@gmail.com>
Date: Mon, 1 Mar 2021 23:07:25 +0100
Subject: [PATCH] Set idle priority for navmesh generation thread

Support Linux, Windows, FreeBSD.
---
 components/CMakeLists.txt                     |  2 +-
 .../detournavigator/asyncnavmeshupdater.cpp   |  2 +
 components/misc/thread.cpp                    | 73 +++++++++++++++++++
 components/misc/thread.hpp                    | 11 +++
 4 files changed, 87 insertions(+), 1 deletion(-)
 create mode 100644 components/misc/thread.cpp
 create mode 100644 components/misc/thread.hpp

diff --git a/components/CMakeLists.txt b/components/CMakeLists.txt
index 822858c0b..ad2783b57 100644
--- a/components/CMakeLists.txt
+++ b/components/CMakeLists.txt
@@ -87,7 +87,7 @@ add_component_dir (esmterrain
     )
 
 add_component_dir (misc
-    constants utf8stream stringops resourcehelpers rng messageformatparser weakcache
+    constants utf8stream stringops resourcehelpers rng messageformatparser weakcache thread
     )
 
 add_component_dir (debug
diff --git a/components/detournavigator/asyncnavmeshupdater.cpp b/components/detournavigator/asyncnavmeshupdater.cpp
index 1ac928f07..bb78df764 100644
--- a/components/detournavigator/asyncnavmeshupdater.cpp
+++ b/components/detournavigator/asyncnavmeshupdater.cpp
@@ -4,6 +4,7 @@
 #include "settings.hpp"
 
 #include <components/debug/debuglog.hpp>
+#include <components/misc/thread.hpp>
 
 #include <osg/Stats>
 
@@ -135,6 +136,7 @@ namespace DetourNavigator
     void AsyncNavMeshUpdater::process() noexcept
     {
         Log(Debug::Debug) << "Start process navigator jobs by thread=" << std::this_thread::get_id();
+        Misc::setCurrentThreadIdlePriority();
         while (!mShouldStop)
         {
             try
diff --git a/components/misc/thread.cpp b/components/misc/thread.cpp
new file mode 100644
index 000000000..8101779bc
--- /dev/null
+++ b/components/misc/thread.cpp
@@ -0,0 +1,73 @@
+#include "thread.hpp"
+
+#include <components/debug/debuglog.hpp>
+
+#include <cstring>
+#include <thread>
+
+#ifdef __linux__
+
+#include <pthread.h>
+#include <sched.h>
+
+namespace Misc
+{
+    void setCurrentThreadIdlePriority()
+    {
+        sched_param param;
+        param.sched_priority = 0;
+        if (pthread_setschedparam(pthread_self(), SCHED_IDLE, &param) == 0)
+            Log(Debug::Verbose) << "Using idle priority for thread=" << std::this_thread::get_id();
+        else
+            Log(Debug::Warning) << "Failed to set idle priority for thread=" << std::this_thread::get_id() << ": " << std::strerror(errno);
+    }
+}
+
+#elif defined(WIN32)
+
+#undef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+
+#include <windows.h>
+
+namespace Misc
+{
+    void setCurrentThreadIdlePriority()
+    {
+        if (SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_LOWEST))
+            Log(Debug::Verbose) << "Using idle priority for thread=" << std::this_thread::get_id();
+        else
+            Log(Debug::Warning) << "Failed to set idle priority for thread=" << std::this_thread::get_id() << ": " << GetLastError();
+    }
+}
+
+#elif defined(__FreeBSD__)
+
+#include <sys/types.h>
+#include <sys/rtprio.h>
+
+namespace Misc
+{
+    void setCurrentThreadIdlePriority()
+    {
+        rtprio prio;
+        prio.type = RTP_PRIO_IDLE;
+        prio.prio = RTP_PRIO_MAX;
+        if (rtprio_thread(RTP_SET, 0, &prio) == 0)
+            Log(Debug::Verbose) << "Using idle priority for thread=" << std::this_thread::get_id();
+        else
+            Log(Debug::Warning) << "Failed to set idle priority for thread=" << std::this_thread::get_id() << ": " << std::strerror(errno);
+    }
+}
+
+#else
+
+namespace Misc
+{
+    void setCurrentThreadIdlePriority()
+    {
+        Log(Debug::Warning) << "Idle thread priority is not supported on this system";
+    }
+}
+
+#endif
diff --git a/components/misc/thread.hpp b/components/misc/thread.hpp
new file mode 100644
index 000000000..191c43bba
--- /dev/null
+++ b/components/misc/thread.hpp
@@ -0,0 +1,11 @@
+#ifndef OPENMW_COMPONENTS_MISC_THREAD_H
+#define OPENMW_COMPONENTS_MISC_THREAD_H
+
+#include <thread>
+
+namespace Misc
+{
+    void setCurrentThreadIdlePriority();
+}
+
+#endif