/*
* The garbage collection daemon. Initiates a concurrent collection
* when signaled. Also periodically trims the heaps when a few seconds
* have elapsed since the last concurrent GC.
*/
static void *gcDaemonThread(void* arg)
{
dvmChangeStatus(NULL, THREAD_VMWAIT);
dvmLockMutex(&gHs->gcThreadMutex);
while (gHs->gcThreadShutdown != true) {
bool trim = false;
if (gHs->gcThreadTrimNeeded) {
int result = dvmRelativeCondWait(&gHs->gcThreadCond, &gHs->gcThreadMutex,
HEAP_TRIM_IDLE_TIME_MS, 0);
if (result == ETIMEDOUT) {
/* Timed out waiting for a GC request, schedule a heap trim. */
trim = true;
}
} else {
dvmWaitCond(&gHs->gcThreadCond, &gHs->gcThreadMutex);
}
// Many JDWP requests cause allocation. We can't take the heap lock and wait to
// transition to runnable so we can start a GC if a debugger is connected, because
// we don't know that the JDWP thread isn't about to allocate and require the
// heap lock itself, leading to deadlock. http://b/8191824.
if (gDvm.debuggerConnected) {
continue;
}
dvmLockHeap();
/*
* Another thread may have started a concurrent garbage
* collection before we were scheduled. Check for this
* condition before proceeding.
*/
if (!gDvm.gcHeap->gcRunning) {
dvmChangeStatus(NULL, THREAD_RUNNING);
if (trim) {
trimHeaps();
gHs->gcThreadTrimNeeded = false;
} else {
dvmCollectGarbageInternal(GC_CONCURRENT);
gHs->gcThreadTrimNeeded = true;
}
dvmChangeStatus(NULL, THREAD_VMWAIT);
}
dvmUnlockHeap();
}
dvmChangeStatus(NULL, THREAD_RUNNING);
return NULL;
}
/* Block until the queue length is 0, or there is a pending suspend request */
void dvmCompilerDrainQueue(void)
{
Thread *self = dvmThreadSelf();
dvmLockMutex(&gDvmJit.compilerLock);
while (workQueueLength() != 0 && !gDvmJit.haltCompilerThread &&
self->suspendCount == 0) {
/*
* Use timed wait here - more than one mutator threads may be blocked
* but the compiler thread will only signal once when the queue is
* emptied. Furthermore, the compiler thread may have been shutdown
* so the blocked thread may never get the wakeup signal.
*/
dvmRelativeCondWait(&gDvmJit.compilerQueueEmpty, &gDvmJit.compilerLock, 1000, 0);
}
dvmUnlockMutex(&gDvmJit.compilerLock);
}
/**
* @brief 丢弃编译队列
*/
void dvmCompilerDrainQueue(void)
{
Thread *self = dvmThreadSelf();
dvmLockMutex(&gDvmJit.compilerLock);
/* 遍历整个队列，并不停的检测编译线程是否终止，并且自身线程没有被挂起 */
while (workQueueLength() != 0 && !gDvmJit.haltCompilerThread &&
self->suspendCount == 0) {
/*
* Use timed wait here - more than one mutator threads may be blocked
* but the compiler thread will only signal once when the queue is
* emptied. Furthermore, the compiler thread may have been shutdown
* so the blocked thread may never get the wakeup signal.
*/
/* 使用等待时间 - 超过一个mutator线程被阻塞但是编译器线程将
* 仅有一条一次当队列被提交，编译器线程不关闭，阻塞线程将永远不会唤醒*/
dvmRelativeCondWait(&gDvmJit.compilerQueueEmpty, &gDvmJit.compilerLock, 1000, 0);
}
dvmUnlockMutex(&gDvmJit.compilerLock);
}
/*
* The garbage collection daemon. Initiates a concurrent collection
* when signaled. Also periodically trims the heaps when a few seconds
* have elapsed since the last concurrent GC.
*/
static void *gcDaemonThread(void* arg)
{
dvmChangeStatus(NULL, THREAD_VMWAIT);
dvmLockMutex(&gHs->gcThreadMutex);
while (gHs->gcThreadShutdown != true) {
bool trim = false;
if (gHs->gcThreadTrimNeeded) {
int result = dvmRelativeCondWait(&gHs->gcThreadCond, &gHs->gcThreadMutex,
HEAP_TRIM_IDLE_TIME_MS, 0);
if (result == ETIMEDOUT) {
/* Timed out waiting for a GC request, schedule a heap trim. */
trim = true;
}
} else {
dvmWaitCond(&gHs->gcThreadCond, &gHs->gcThreadMutex);
}
dvmLockHeap();
/*
* Another thread may have started a concurrent garbage
* collection before we were scheduled. Check for this
* condition before proceeding.
*/
if (!gDvm.gcHeap->gcRunning) {
dvmChangeStatus(NULL, THREAD_RUNNING);
if (trim) {
trimHeaps();
gHs->gcThreadTrimNeeded = false;
} else {
dvmCollectGarbageInternal(GC_CONCURRENT);
gHs->gcThreadTrimNeeded = true;
}
dvmChangeStatus(NULL, THREAD_VMWAIT);
}
dvmUnlockHeap();
}
dvmChangeStatus(NULL, THREAD_RUNNING);
return NULL;
}
static void *compilerThreadStart(void *arg)
{
dvmChangeStatus(NULL, THREAD_VMWAIT);
/*
* If we're not running stand-alone, wait a little before
* recieving translation requests on the assumption that process start
* up code isn't worth compiling. We'll resume when the framework
* signals us that the first screen draw has happened, or the timer
* below expires (to catch daemons).
*
* There is a theoretical race between the callback to
* VMRuntime.startJitCompiation and when the compiler thread reaches this
* point. In case the callback happens earlier, in order not to permanently
* hold the system_server (which is not using the timed wait) in
* interpreter-only mode we bypass the delay here.
*/
if (gDvmJit.runningInAndroidFramework &&
!gDvmJit.alreadyEnabledViaFramework) {
/*
* If the current VM instance is the system server (detected by having
* 0 in gDvm.systemServerPid), we will use the indefinite wait on the
* conditional variable to determine whether to start the JIT or not.
* If the system server detects that the whole system is booted in
* safe mode, the conditional variable will never be signaled and the
* system server will remain in the interpreter-only mode. All
* subsequent apps will be started with the --enable-safemode flag
* explicitly appended.
*/
if (gDvm.systemServerPid == 0) {
dvmLockMutex(&gDvmJit.compilerLock);
pthread_cond_wait(&gDvmJit.compilerQueueActivity,
&gDvmJit.compilerLock);
dvmUnlockMutex(&gDvmJit.compilerLock);
ALOGD("JIT started for system_server");
} else {
dvmLockMutex(&gDvmJit.compilerLock);
/*
* TUNING: experiment with the delay & perhaps make it
* target-specific
*/
dvmRelativeCondWait(&gDvmJit.compilerQueueActivity,
&gDvmJit.compilerLock, 3000, 0);
dvmUnlockMutex(&gDvmJit.compilerLock);
}
if (gDvmJit.haltCompilerThread) {
return NULL;
}
}
compilerThreadStartup();
dvmLockMutex(&gDvmJit.compilerLock);
/*
* Since the compiler thread will not touch any objects on the heap once
* being created, we just fake its state as VMWAIT so that it can be a
* bit late when there is suspend request pending.
*/
while (!gDvmJit.haltCompilerThread) {
if (workQueueLength() == 0) {
int cc;
cc = pthread_cond_signal(&gDvmJit.compilerQueueEmpty);
assert(cc == 0);
pthread_cond_wait(&gDvmJit.compilerQueueActivity,
&gDvmJit.compilerLock);
continue;
} else {
do {
CompilerWorkOrder work = workDequeue();
dvmUnlockMutex(&gDvmJit.compilerLock);
#if defined(WITH_JIT_TUNING)
/*
* This is live across setjmp(). Mark it volatile to suppress
* a gcc warning. We should not need this since it is assigned
* only once but gcc is not smart enough.
*/
volatile u8 startTime = dvmGetRelativeTimeUsec();
#endif
/*
* Check whether there is a suspend request on me. This
* is necessary to allow a clean shutdown.
*
* However, in the blocking stress testing mode, let the
* compiler thread continue doing compilations to unblock
* other requesting threads. This may occasionally cause
* shutdown from proceeding cleanly in the standalone invocation
* of the vm but this should be acceptable.
*/
if (!gDvmJit.blockingMode)
dvmCheckSuspendPending(dvmThreadSelf());
/* Is JitTable filling up? */
if (gDvmJit.jitTableEntriesUsed >
(gDvmJit.jitTableSize - gDvmJit.jitTableSize/4)) {
bool resizeFail =
dvmJitResizeJitTable(gDvmJit.jitTableSize * 2);
/*
* If the jit table is full, consider it's time to reset
* the code cache too.
*/
gDvmJit.codeCacheFull |= resizeFail;
}
if (gDvmJit.haltCompilerThread) {
ALOGD("Compiler shutdown in progress - discarding request");
} else if (!gDvmJit.codeCacheFull) {
jmp_buf jmpBuf;
work.bailPtr = &jmpBuf;
bool aborted = setjmp(jmpBuf);
if (!aborted) {
bool codeCompiled = dvmCompilerDoWork(&work);
/*
* Make sure we are still operating with the
* same translation cache version. See
* Issue 4271784 for details.
*/
dvmLockMutex(&gDvmJit.compilerLock);
if ((work.result.cacheVersion ==
gDvmJit.cacheVersion) &&
codeCompiled &&
!work.result.discardResult &&
work.result.codeAddress) {
dvmJitSetCodeAddr(work.pc, work.result.codeAddress,
work.result.instructionSet,
false, /* not method entry */
work.result.profileCodeSize);
}
dvmUnlockMutex(&gDvmJit.compilerLock);
}
dvmCompilerArenaReset();
}
free(work.info);
#if defined(WITH_JIT_TUNING)
gDvmJit.jitTime += dvmGetRelativeTimeUsec() - startTime;
#endif
dvmLockMutex(&gDvmJit.compilerLock);
} while (workQueueLength() != 0);
}
}
pthread_cond_signal(&gDvmJit.compilerQueueEmpty);
dvmUnlockMutex(&gDvmJit.compilerLock);
/*
* As part of detaching the thread we need to call into Java code to update
* the ThreadGroup, and we should not be in VMWAIT state while executing
* interpreted code.
*/
dvmChangeStatus(NULL, THREAD_RUNNING);
if (gDvm.verboseShutdown)
ALOGD("Compiler thread shutting down");
return NULL;
}
