void dvmCompilerUpdateGlobalState()
{
bool jitActive;
bool jitActivate;
bool needUnchain = false;
/*
* The tableLock might not be initialized yet by the compiler thread if
* debugger is attached from the very beginning of the VM launch. If
* pProfTableCopy is NULL, the lock is not initialized yet and we don't
* need to refresh anything either.
*/
if (gDvmJit.pProfTableCopy == NULL) {
return;
}
/*
* On the first enabling of method tracing, switch the compiler
* into a mode that includes trace support for invokes and returns.
* If there are any existing translations, flush them. NOTE: we
* can't blindly flush the translation cache because this code
* may be executed before the compiler thread has finished
* initialization.
*/
if ((gDvm.activeProfilers != 0) &&
!gDvmJit.methodTraceSupport) {
bool resetRequired;
/*
* compilerLock will prevent new compilations from being
* installed while we are working.
*/
dvmLockMutex(&gDvmJit.compilerLock);
gDvmJit.cacheVersion++; // invalidate compilations in flight
gDvmJit.methodTraceSupport = true;
resetRequired = (gDvmJit.numCompilations != 0);
dvmUnlockMutex(&gDvmJit.compilerLock);
if (resetRequired) {
dvmSuspendAllThreads(SUSPEND_FOR_CC_RESET);
resetCodeCache();
dvmResumeAllThreads(SUSPEND_FOR_CC_RESET);
}
}
dvmLockMutex(&gDvmJit.tableLock);
jitActive = gDvmJit.pProfTable != NULL;
jitActivate = !dvmDebuggerOrProfilerActive();
if (jitActivate && !jitActive) {
gDvmJit.pProfTable = gDvmJit.pProfTableCopy;
} else if (!jitActivate && jitActive) {
gDvmJit.pProfTable = NULL;
needUnchain = true;
}
dvmUnlockMutex(&gDvmJit.tableLock);
if (needUnchain)
dvmJitUnchainAll();
// Make sure all threads have current values
dvmJitUpdateThreadStateAll();
}
/**
* 关闭Jit编译器
*/
void dvmCompilerShutdown(void)
{
void *threadReturn;
/* Disable new translation requests */
/* 关闭新的编译请求 */
gDvmJit.pProfTable = NULL;
gDvmJit.pProfTableCopy = NULL;
dvmJitUpdateThreadStateAll(); /* 更新所有线程状态 */
/*
* 以下代码应该是检测在虚拟机关闭之前等待所有编译工作队列完成
* dvmCompilerDumpStats()函数应该会更新所有工作队列的当前状态
* gDvmJit.compilerQueueLength会随着这个函数进行更新，这个常数
* 即是当前工作队列的数量。
*/
if (gDvm.verboseShutdown ||
gDvmJit.profileMode == kTraceProfilingContinuous) {
dvmCompilerDumpStats();
while (gDvmJit.compilerQueueLength)
sleep(5);
}
/* 如果编译器工作线程存在 */
if (gDvmJit.compilerHandle) {
gDvmJit.haltCompilerThread = true; /* 设置关闭标志为true */
/* 发送关闭信号 */
dvmLockMutex(&gDvmJit.compilerLock);
pthread_cond_signal(&gDvmJit.compilerQueueActivity);
dvmUnlockMutex(&gDvmJit.compilerLock);
/* 关闭compilerThreadStart线程 */
if (pthread_join(gDvmJit.compilerHandle, &threadReturn) != 0)
ALOGW("Compiler thread join failed");
else if (gDvm.verboseShutdown)
ALOGD("Compiler thread has shut down");
}
/* Break loops within the translation cache */
dvmJitUnchainAll();
/*
* NOTE: our current implementatation doesn't allow for the compiler
* thread to be restarted after it exits here. We aren't freeing
* the JitTable or the ProfTable because threads which still may be
* running or in the process of shutting down may hold references to
*
* them.
*/
}
/*
* Respond to a SIGUSR2 by dumping some JIT stats and possibly resetting
* the code cache.
*/
static void handleSigUsr2()
{
static int codeCacheResetCount = 0;
gDvmJit.receivedSIGUSR2 ^= true;
if ((--codeCacheResetCount & 7) == 0) {
/* Dump all class pointers in the traces */
dvmJitScanAllClassPointers(printAllClass);
gDvmJit.codeCacheFull = true;
} else {
dvmCompilerDumpStats();
/* Stress-test unchain all */
dvmJitUnchainAll();
ALOGD("Send %d more signals to reset the code cache",
codeCacheResetCount & 7);
}
dvmCheckInterpStateConsistency();
}
void dvmCompilerShutdown(void)
{
void *threadReturn;
/* Disable new translation requests */
gDvmJit.pProfTable = NULL;
gDvmJit.pProfTableCopy = NULL;
dvmJitUpdateThreadStateAll();
if (gDvm.verboseShutdown ||
gDvmJit.profileMode == kTraceProfilingContinuous) {
dvmCompilerDumpStats();
while (gDvmJit.compilerQueueLength)
sleep(5);
}
if (gDvmJit.compilerHandle) {
gDvmJit.haltCompilerThread = true;
dvmLockMutex(&gDvmJit.compilerLock);
pthread_cond_signal(&gDvmJit.compilerQueueActivity);
dvmUnlockMutex(&gDvmJit.compilerLock);
if (pthread_join(gDvmJit.compilerHandle, &threadReturn) != 0)
ALOGW("Compiler thread join failed");
else if (gDvm.verboseShutdown)
ALOGD("Compiler thread has shut down");
}
/* Break loops within the translation cache */
dvmJitUnchainAll();
/*
* NOTE: our current implementatation doesn't allow for the compiler
* thread to be restarted after it exits here. We aren't freeing
* the JitTable or the ProfTable because threads which still may be
* running or in the process of shutting down may hold references to
* them.
*/
}
/**
* @brief 更新编译器全局状态
* @note 在"vm/Profile.cpp"中的updateActiveProfilers中被调用
*/
void dvmCompilerUpdateGlobalState()
{
bool jitActive;
bool jitActivate;
bool needUnchain = false;
/*
* The tableLock might not be initialized yet by the compiler thread if
* debugger is attached from the very beginning of the VM launch. If
* pProfTableCopy is NULL, the lock is not initialized yet and we don't
* need to refresh anything either.
*/
/*
* 如果在调试器附加到虚拟机启动器的非常早之前，编译器线程对tableLock
* 并没有初始化完成。这是我们不能更新任何状态。
*/
if (gDvmJit.pProfTableCopy == NULL) {
return;
}
/*
* On the first enabling of method tracing, switch the compiler
* into a mode that includes trace support for invokes and returns.
* If there are any existing translations, flush them. NOTE: we
* can't blindly flush the translation cache because this code
* may be executed before the compiler thread has finished
* initialization.
*/
/*
* 第一次启用函数tracing，转化编译器到保护支持invokes与returns
* 指令的trace格式。如果已经存在了一些编译代码则直接刷入他们到缓存中。
* NOTE：我们不能在编译器线程未初始化完成之前刷入代码
*/
/* activeProfilers 表明 开启profiler */
if ((gDvm.activeProfilers != 0) &&
!gDvmJit.methodTraceSupport) { /* 这里表明第一次启动tracing */
bool resetRequired;
/*
* compilerLock will prevent new compilations from being
* installed while we are working.
*/
dvmLockMutex(&gDvmJit.compilerLock);
/* 增加缓冲版本，无效编译 */
gDvmJit.cacheVersion++; // invalidate compilations in flight
gDvmJit.methodTraceSupport = true; /* 开启 */
resetRequired = (gDvmJit.numCompilations != 0); /* 检测是否重设代码缓冲区*/
dvmUnlockMutex(&gDvmJit.compilerLock);
if (resetRequired) {
dvmSuspendAllThreads(SUSPEND_FOR_CC_RESET);
resetCodeCache(); /* 重新更新代码缓冲区 */
dvmResumeAllThreads(SUSPEND_FOR_CC_RESET);
}
}
dvmLockMutex(&gDvmJit.tableLock);
/* 通过判断pProfTable表判断JIT是否被激活 */
jitActive = gDvmJit.pProfTable != NULL;
jitActivate = !dvmDebuggerOrProfilerActive(); /* 处于调试阶段或者profile开启 */
/* jitActivate为TRUE表明处于调试阶段 */
if (jitActivate && !jitActive) {
gDvmJit.pProfTable = gDvmJit.pProfTableCopy; /* 处于调试获取副本 */
} else if (!jitActivate && jitActive) { /* 处于正常运行 */
gDvmJit.pProfTable = NULL;
needUnchain = true;/* 需要解链操作 */
}
dvmUnlockMutex(&gDvmJit.tableLock);
if (needUnchain) /* 不再调试模式下为TRUE */
dvmJitUnchainAll();
// Make sure all threads have current values
/* 对所有线程设置JitTable表 */
dvmJitUpdateThreadStateAll();
}
