From a95dacafdf95b7b29484383eabb5ed49e0126bec Mon Sep 17 00:00:00 2001
From: Peter Osterlund <peterosterlund2@gmail.com>
Date: Sat, 24 Oct 2015 00:11:21 +0200
Subject: [PATCH] DroidFish: Run the engine process with lower priority.

---
 DroidFish/jni/nativeutil.cpp                     | 16 ++++++++++++++--
 .../org/petero/droidfish/engine/EngineUtil.java  |  3 +++
 .../petero/droidfish/engine/ExternalEngine.java  | 12 ++++++++++++
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/DroidFish/jni/nativeutil.cpp b/DroidFish/jni/nativeutil.cpp
index 7ff5c85..de93aa2 100644
--- a/DroidFish/jni/nativeutil.cpp
+++ b/DroidFish/jni/nativeutil.cpp
@@ -20,6 +20,8 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/resource.h>
 
 /*
  * Class:     org_petero_droidfish_engine_EngineUtil
@@ -27,8 +29,7 @@
  * Signature: (Ljava/lang/String;)Z
  */
 extern "C" JNIEXPORT jboolean JNICALL Java_org_petero_droidfish_engine_EngineUtil_chmod
-  (JNIEnv *env, jclass, jstring jExePath)
-{
+  (JNIEnv *env, jclass, jstring jExePath) {
     const char* exePath = (*env).GetStringUTFChars(jExePath, NULL);
     if (!exePath)
         return false;
@@ -36,3 +37,14 @@ extern "C" JNIEXPORT jboolean JNICALL Java_org_petero_droidfish_engine_EngineUti
     (*env).ReleaseStringUTFChars(jExePath, exePath);
     return ret;
 }
+
+/*
+ * Class:     org_petero_droidfish_engine_EngineUtil
+ * Method:    reNice
+ * Signature: (II)V
+ */
+extern "C" JNIEXPORT void JNICALL Java_org_petero_droidfish_engine_EngineUtil_reNice
+  (JNIEnv *env, jclass, jint pid, jint prio) {
+    setpriority(PRIO_PROCESS, pid, prio);
+}
+
diff --git a/DroidFish/src/org/petero/droidfish/engine/EngineUtil.java b/DroidFish/src/org/petero/droidfish/engine/EngineUtil.java
index 9168b4e..7c00dba 100644
--- a/DroidFish/src/org/petero/droidfish/engine/EngineUtil.java
+++ b/DroidFish/src/org/petero/droidfish/engine/EngineUtil.java
@@ -107,6 +107,9 @@ public class EngineUtil {
     /** Executes chmod 744 exePath. */
     final static native boolean chmod(String exePath);
 
+    /** Change the priority of a process. */
+    final static native void reNice(int pid, int prio);
+
     /** For synchronizing non thread safe native calls. */
     public static Object nativeLock = new Object();
 }
diff --git a/DroidFish/src/org/petero/droidfish/engine/ExternalEngine.java b/DroidFish/src/org/petero/droidfish/engine/ExternalEngine.java
index be3ff57..f96ab60 100644
--- a/DroidFish/src/org/petero/droidfish/engine/ExternalEngine.java
+++ b/DroidFish/src/org/petero/droidfish/engine/ExternalEngine.java
@@ -77,6 +77,7 @@ public class ExternalEngine extends UCIEngineBase {
             synchronized (EngineUtil.nativeLock) {
                 engineProc = pb.start();
             }
+            reNice(engineProc);
 
             startupThread = new Thread(new Runnable() {
                 @Override
@@ -168,6 +169,17 @@ public class ExternalEngine extends UCIEngineBase {
         }
     }
 
+    /** Try to change the engine process priority to 5. */
+    private void reNice(Process proc) {
+        try {
+            java.lang.reflect.Field f = engineProc.getClass().getDeclaredField("pid");
+            f.setAccessible(true);
+            int pid = f.getInt(engineProc);
+            EngineUtil.reNice(pid, 10);
+        } catch (Throwable t) {
+        }
+    }
+
     /** Remove all files except exePath from exeDir. */
     private void cleanUpExeDir(File exeDir, String exePath) {
         try {