android原始碼4.4.2----系統啟動過程分析
阿新 • • 發佈：2019-01-01
public class SystemServer {
private static final String TAG = "SystemServer";
public static final int FACTORY_TEST_OFF = 0;
public static final int FACTORY_TEST_LOW_LEVEL = 1;
public static final int FACTORY_TEST_HIGH_LEVEL = 2;
static Timer timer;
static final long SNAPSHOT_INTERVAL = 60 * 60 * 1000; // 1hr
// The earliest supported time. We pick one day into 1970, to
// give any timezone code room without going into negative time.
private static final long EARLIEST_SUPPORTED_TIME = 86400 * 1000;
/**
* Called to initialize native system services.
*/
private static native void nativeInit();
public static void main(String[] args) {
/*
* In case the runtime switched since last boot (such as when
* the old runtime was removed in an OTA), set the system
* property so that it is in sync. We can't do this in
* libnativehelper's JniInvocation::Init code where we already
* had to fallback to a different runtime because it is
* running as root and we need to be the system user to set
* the property. http://b/11463182
*/
SystemProperties.set("persist.sys.dalvik.vm.lib",
VMRuntime.getRuntime().vmLibrary());
if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {
// If a device's clock is before 1970 (before 0), a lot of
// APIs crash dealing with negative numbers, notably
// java.io.File#setLastModified, so instead we fake it and
// hope that time from cell towers or NTP fixes it
// shortly.
Slog.w(TAG, "System clock is before 1970; setting to 1970.");
SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
}
if (SamplingProfilerIntegration.isEnabled()) {
SamplingProfilerIntegration.start();
timer = new Timer();
timer.schedule(new TimerTask() {
@Override
public void run() {
SamplingProfilerIntegration.writeSnapshot("system_server", null);
}
}, SNAPSHOT_INTERVAL, SNAPSHOT_INTERVAL);
}
// Mmmmmm... more memory!
dalvik.system.VMRuntime.getRuntime().clearGrowthLimit();
// The system server has to run all of the time, so it needs to be
// as efficient as possible with its memory usage.
VMRuntime.getRuntime().setTargetHeapUtilization(0.8f);
Environment.setUserRequired(true);
System.loadLibrary("android_servers");
Slog.i(TAG, "Entered the Android system server!");
// Initialize native services.
nativeInit();
// This used to be its own separate thread, but now it is
// just the loop we run on the main thread.
ServerThread thr = new ServerThread();
thr.initAndLoop();
}
}
1.設定執行環境庫
SystemProperties.set("persist.sys.dalvik.vm.lib",
VMRuntime.getRuntime().vmLibrary());
2.設定系統時間
if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {
// If a device's clock is before 1970 (before 0), a lot of
// APIs crash dealing with negative numbers, notably
// java.io.File#setLastModified, so instead we fake it and
// hope that time from cell towers or NTP fixes it
// shortly.
Slog.w(TAG, "System clock is before 1970; setting to 1970.");
SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
}
3.效能統計
if (SamplingProfilerIntegration.isEnabled()) {
SamplingProfilerIntegration.start();
timer = new Timer();
timer.schedule(new TimerTask() {
@Override
public void run() {
SamplingProfilerIntegration.writeSnapshot("system_server", null);
}
}, SNAPSHOT_INTERVAL, SNAPSHOT_INTERVAL);
}
4.設定記憶體上限
// Mmmmmm... more memory!
dalvik.system.VMRuntime.getRuntime().clearGrowthLimit();
// The system server has to run all of the time, so it needs to be
// as efficient as possible with its memory usage.
VMRuntime.getRuntime().setTargetHeapUtilization(0.8f);
5.設定使用者，否則無法使用環境變數
Environment.setUserRequired(true);
6.載入系統服務庫
System.loadLibrary("android_servers");
7.初始化本地服務----SensorService--硬體相關
nativeInit();
static void android_server_SystemServer_nativeInit(JNIEnv* env, jobject clazz) {
char propBuf[PROPERTY_VALUE_MAX];
property_get("system_init.startsensorservice", propBuf, "1");
if (strcmp(propBuf, "1") == 0) {
// Start the sensor service
SensorService::instantiate();
}
}
8.系統服務執行緒--完成系統各種服務的啟動
ServerThread thr = new ServerThread();
thr.initAndLoop();
private static final String TAG = "SystemServer";
public static final int FACTORY_TEST_OFF = 0;
public static final int FACTORY_TEST_LOW_LEVEL = 1;
public static final int FACTORY_TEST_HIGH_LEVEL = 2;
static Timer timer;
static final long SNAPSHOT_INTERVAL = 60 * 60 * 1000; // 1hr
// The earliest supported time. We pick one day into 1970, to
// give any timezone code room without going into negative time.
private static final long EARLIEST_SUPPORTED_TIME = 86400 * 1000;
/**
* Called to initialize native system services.
*/
private static native void nativeInit();
public static void main(String[] args) {
/*
* In case the runtime switched since last boot (such as when
* the old runtime was removed in an OTA), set the system
* property so that it is in sync. We can't do this in
* libnativehelper's JniInvocation::Init code where we already
* had to fallback to a different runtime because it is
* running as root and we need to be the system user to set
* the property. http://b/11463182
*/
SystemProperties.set("persist.sys.dalvik.vm.lib",
VMRuntime.getRuntime().vmLibrary());
if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {
// If a device's clock is before 1970 (before 0), a lot of
// APIs crash dealing with negative numbers, notably
// java.io.File#setLastModified, so instead we fake it and
// hope that time from cell towers or NTP fixes it
// shortly.
Slog.w(TAG, "System clock is before 1970; setting to 1970.");
SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
}
if (SamplingProfilerIntegration.isEnabled()) {
SamplingProfilerIntegration.start();
timer = new Timer();
timer.schedule(new TimerTask() {
@Override
public void run() {
SamplingProfilerIntegration.writeSnapshot("system_server", null);
}
}, SNAPSHOT_INTERVAL, SNAPSHOT_INTERVAL);
}
// Mmmmmm... more memory!
dalvik.system.VMRuntime.getRuntime().clearGrowthLimit();
// The system server has to run all of the time, so it needs to be
// as efficient as possible with its memory usage.
VMRuntime.getRuntime().setTargetHeapUtilization(0.8f);
Environment.setUserRequired(true);
System.loadLibrary("android_servers");
Slog.i(TAG, "Entered the Android system server!");
// Initialize native services.
nativeInit();
// This used to be its own separate thread, but now it is
// just the loop we run on the main thread.
ServerThread thr = new ServerThread();
thr.initAndLoop();
}
}
1.設定執行環境庫
SystemProperties.set("persist.sys.dalvik.vm.lib",
VMRuntime.getRuntime().vmLibrary());
2.設定系統時間
if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {
// If a device's clock is before 1970 (before 0), a lot of
// APIs crash dealing with negative numbers, notably
// java.io.File#setLastModified, so instead we fake it and
// hope that time from cell towers or NTP fixes it
// shortly.
Slog.w(TAG, "System clock is before 1970; setting to 1970.");
SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
}
3.效能統計
if (SamplingProfilerIntegration.isEnabled()) {
SamplingProfilerIntegration.start();
timer = new Timer();
timer.schedule(new TimerTask() {
@Override
public void run() {
SamplingProfilerIntegration.writeSnapshot("system_server", null);
}
}, SNAPSHOT_INTERVAL, SNAPSHOT_INTERVAL);
}
4.設定記憶體上限
// Mmmmmm... more memory!
dalvik.system.VMRuntime.getRuntime().clearGrowthLimit();
// The system server has to run all of the time, so it needs to be
// as efficient as possible with its memory usage.
VMRuntime.getRuntime().setTargetHeapUtilization(0.8f);
5.設定使用者，否則無法使用環境變數
Environment.setUserRequired(true);
6.載入系統服務庫
System.loadLibrary("android_servers");
7.初始化本地服務----SensorService--硬體相關
nativeInit();
static void android_server_SystemServer_nativeInit(JNIEnv* env, jobject clazz) {
char propBuf[PROPERTY_VALUE_MAX];
property_get("system_init.startsensorservice", propBuf, "1");
if (strcmp(propBuf, "1") == 0) {
// Start the sensor service
SensorService::instantiate();
}
}
8.系統服務執行緒--完成系統各種服務的啟動
ServerThread thr = new ServerThread();
thr.initAndLoop();