Android: Pin emu thread to exclusive cores where supported

android/app/src/cpp/android_host_interface.cpp

@@ -22,6 +22,8 @@
 #include "scmversion/scmversion.h"
 #include <android/native_window_jni.h>
 #include <cmath>
+#include <unistd.h>
+#include <sched.h>
 #include <imgui.h>
 Log_SetChannel(AndroidHostInterface);
 
@@ -952,6 +954,31 @@ DEFINE_JNI_ARGS_METHOD(jstring, AndroidHostInterface_getFullScmVersion, jobject
                                                    g_scm_branch_str, __DATE__, __TIME__));
 }
 
+DEFINE_JNI_ARGS_METHOD(void, AndroidHostInterface_setThreadAffinity, jobject unused, jintArray cores)
+{
+  // https://github.com/googlearchive/android-audio-high-performance/blob/c232c21bf35d3bfea16537b781c526b8abdcc3cf/SimpleSynth/app/src/main/cpp/audio_player.cc
+  int length = env->GetArrayLength(cores);
+  int* p_cores = env->GetIntArrayElements(cores, nullptr);
+
+  pid_t current_thread_id = gettid();
+  cpu_set_t cpu_set;
+  CPU_ZERO(&cpu_set);
+  for (int i = 0; i < length; i++)
+  {
+    Log_InfoPrintf("Binding to CPU %d", p_cores[i]);
+    CPU_SET(p_cores[i], &cpu_set);
+  }
+
+  int result = sched_setaffinity(current_thread_id, sizeof(cpu_set_t), &cpu_set);
+  if (result != 0)
+    Log_InfoPrintf("Thread affinity set.");
+  else
+    Log_ErrorPrintf("Error setting thread affinity: %d", result);
+
+  env->ReleaseIntArrayElements(cores, p_cores, 0);
+}
+
+
 DEFINE_JNI_ARGS_METHOD(jobject, AndroidHostInterface_create, jobject unused, jobject context_object,
                        jstring user_directory)
 {

android/app/src/main/java/com/github/stenzek/duckstation/AndroidHostInterface.java

@@ -45,6 +45,8 @@ public class AndroidHostInterface {
 
     static public native String getFullScmVersion();
 
+    static public native boolean setThreadAffinity(int[] cpus);
+
     static public native AndroidHostInterface create(Context context, String userDirectory);
 
     public native boolean isEmulationThreadRunning();

android/app/src/main/java/com/github/stenzek/duckstation/EmulationThread.java

@@ -1,5 +1,6 @@
 package com.github.stenzek.duckstation;
 
+import android.os.Build;
 import android.os.Process;
 import android.util.Log;
 import android.view.Surface;
@@ -28,10 +29,25 @@ public class EmulationThread extends Thread {
         return thread;
     }
 
+    private void setExclusiveCores() {
+        try {
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
+                int[] cores = Process.getExclusiveCores();
+                if (cores == null || cores.length == 0)
+                    throw new Exception("Invalid return value from getExclusiveCores()");
+
+                AndroidHostInterface.setThreadAffinity(cores);
+            }
+        } catch (Exception e) {
+            Log.e("EmulationThread", "getExclusiveCores() failed");
+        }
+    }
+
     @Override
     public void run() {
         try {
             Process.setThreadPriority(Process.THREAD_PRIORITY_MORE_FAVORABLE);
+            setExclusiveCores();
         } catch (Exception e) {
             Log.i("EmulationThread", "Failed to set priority for emulation thread: " + e.getMessage());
         }