文中所有代碼基于Android8.0

不了解dumpsys，可以先看Android dumpsys 實(shí)現(xiàn)

1.執(zhí)行dump

測(cè)試android性能，其中幀率很重要，執(zhí)行adb shell dumpsys graphicsstats，能得到類似如下結(jié)果：

... //包名 Package: android //系統(tǒng)開機(jī)多久后開始統(tǒng)計(jì)的 Stats since: 253812513812ns //總共繪制的幀數(shù) Total frames rendered: 479 //卡頓幀數(shù)，16ms沒繪制完的 Janky frames: 25(5.23%) // 50% 90% 95% 99% 的幀數(shù)是多長時(shí)間繪制完成的 50th percentile: 5ms 90th percentile: 23ms 95th percentile: 35ms 99th percentile: 43ms// 丟失的Vsync信號(hào) Number Missed Vsync: 12 //高輸入導(dǎo)致的 Number High input latency: 0 //ui線程慢 Number Slow UI thread: 7 //上傳繪制bitmap Number Slow bitmap uploads: 3 //繪制命令異常 Number Slow issue draw commands: 15// 這是每個(gè)時(shí)間對(duì)應(yīng)的繪制幀數(shù) HISTOGRAM: 5ms=4620 6ms=622 7ms=328 8ms=198 9ms=332 ...非常多... 4150ms=0 4200ms=0 4250ms=0 4300ms=0 4350ms=0 4400ms=0 4450ms=0 4500ms=0 4550ms=0 4600ms=0 4650ms=0 4700ms=0 4750ms=0 4800ms=0 4850ms=0 4900ms=0 4950ms=0 ... 復(fù)制代碼

2 執(zhí)行流程

主要用到的類： GraphicsStatsService.java com_android_server_GraphicsStatsService.cpp GraphicsStatsService.cpp

Android dumpsys 實(shí)現(xiàn)一文提到如何service是如何dump的，graphicsstats這個(gè)對(duì)應(yīng)的服務(wù)是GraphicsStatsService,看一下它是如何將數(shù)據(jù)dump的。 所有的系統(tǒng)服務(wù)從binder繼承的dump接口，在GraphicsStatsService.java中：

@Overrideprotected void dump(FileDescriptor fd, PrintWriter fout, String[] args) {if (!DumpUtils.checkDumpAndUsageStatsPermission(mContext, TAG, fout)) return;//1 解析參數(shù)boolean dumpProto = false;for (String str : args) {if ("--proto".equals(str)) {dumpProto = true;break;}}//2 收集buffersArrayList<HistoricalBuffer> buffers;synchronized (mLock) {buffers = new ArrayList<>(mActive.size());for (int i = 0; i < mActive.size(); i++) {try {buffers.add(new HistoricalBuffer(mActive.get(i)));} catch (IOException ex) {// Ignore}}}//3 創(chuàng)建dump對(duì)象long dump = nCreateDump(fd.getInt$(), dumpProto);try {synchronized (mFileAccessLock) {//4 dump數(shù)據(jù)HashSet<File> skipList = dumpActiveLocked(dump, buffers);buffers.clear();dumpHistoricalLocked(dump, skipList);}} finally {// 5 完成dumpnFinishDump(dump);}} 復(fù)制代碼

2.1 解析參數(shù)，當(dāng) dump graphicsstats --proto 時(shí)，加了這個(gè)參數(shù)會(huì)按proto格式打印，反正人沒法認(rèn)出來... 2.2 收集buffer，這步比較重要,看兩個(gè)數(shù)據(jù)結(jié)構(gòu)ActiveBuffer 和 HistoricalBuffer

private final class ActiveBuffer implements DeathRecipient {...MemoryFile mProcessBuffer;ActiveBuffer(IGraphicsStatsCallback token, int uid, int pid, String packageName, int versionCode)throws RemoteException, IOException {...// 創(chuàng)建 MemoryFilemProcessBuffer = new MemoryFile("GFXStats-" + pid, ASHMEM_SIZE);mProcessBuffer.writeBytes(ZERO_DATA, 0, 0, ASHMEM_SIZE);}....}private final class HistoricalBuffer {final BufferInfo mInfo;final byte[] mData = new byte[ASHMEM_SIZE];HistoricalBuffer(ActiveBuffer active) throws IOException {mInfo = active.mInfo;mInfo.endTime = System.currentTimeMillis();//讀取數(shù)據(jù)active.mProcessBuffer.readBytes(mData, 0, 0, ASHMEM_SIZE);}}復(fù)制代碼

ActiveBuffer在創(chuàng)建時(shí)，new了一個(gè)MemoryFile，也就是共享內(nèi)存，并且初始化為0值。在繪制時(shí)會(huì)將數(shù)據(jù)填充。當(dāng)收集buffer時(shí)，在HistoricalBuffer里，將數(shù)據(jù)讀到了它的成員mData中，其大小為ASHMEM_SIZE，是通過一個(gè)native方法拿到的：

# com_android_server_GraphicsStatsService.cppstatic jint getAshmemSize(JNIEnv*, jobject) {return sizeof(ProfileData); } 復(fù)制代碼

是一個(gè)名為ProfileData的結(jié)構(gòu)體的大小。（下一篇聊這個(gè)結(jié)構(gòu)體，它關(guān)乎數(shù)據(jù)的來源）這樣數(shù)據(jù)就收集完了。

2.3 創(chuàng)建dump，在底層做了什么呢？

long dump = nCreateDump(fd.getInt$(), dumpProto); 復(fù)制代碼

fd.getInt$(),拿到要寫入的fd。 dumpProto 默認(rèn)是false

static jlong createDump(JNIEnv*, jobject, jint fd, jboolean isProto) {GraphicsStatsService::Dump* dump = GraphicsStatsService::createDump(fd, isProto? GraphicsStatsService::DumpType::Protobuf : GraphicsStatsService::DumpType::Text);return reinterpret_cast<jlong>(dump); } 復(fù)制代碼

原來是new了一個(gè)GrahicsStatsService.cpp里的一個(gè)Dump對(duì)象，然后返回了它的指針。Dump類如下：

class GraphicsStatsService::Dump { public:Dump(int outFd, DumpType type) : mFd(outFd), mType(type) {}int fd() { return mFd; }DumpType type() { return mType; }service::GraphicsStatsServiceDumpProto& proto() { return mProto; } private:int mFd;DumpType mType;service::GraphicsStatsServiceDumpProto mProto; }; 復(fù)制代碼

這個(gè)Dump對(duì)象主要作用是在底層保存了要寫入的fd 。 2.4 上一步得到了一個(gè)底層的指針，接下來就是打印了：

private HashSet<File> dumpActiveLocked(long dump, ArrayList<HistoricalBuffer> buffers) {HashSet<File> skipFiles = new HashSet<>(buffers.size());for (int i = 0; i < buffers.size(); i++) {HistoricalBuffer buffer = buffers.get(i);File path = pathForApp(buffer.mInfo);skipFiles.add(path);nAddToDump(dump, path.getAbsolutePath(), buffer.mInfo.packageName,buffer.mInfo.versionCode, buffer.mInfo.startTime, buffer.mInfo.endTime,buffer.mData);}return skipFiles;} 復(fù)制代碼

主要是nAddToDump這個(gè)方法：

// 去除了一些打印語句 # com_android_server_GraphicsStatsService.cpp static void addToDump(JNIEnv* env, jobject, jlong dumpPtr, jstring jpath, jstring jpackage,jint versionCode, jlong startTime, jlong endTime, jbyteArray jdata) {std::string path;const ProfileData* data = nullptr;ScopedByteArrayRO buffer{env};if (jdata != nullptr) {buffer.reset(jdata);// 1 轉(zhuǎn)換成ProfileData結(jié)構(gòu)data = reinterpret_cast<const ProfileData*>(buffer.get());}if (jpath != nullptr) {ScopedUtfChars pathChars(env, jpath);path.assign(pathChars.c_str(), pathChars.size());}ScopedUtfChars packageChars(env, jpackage);GraphicsStatsService::Dump* dump = reinterpret_cast<GraphicsStatsService::Dump*>(dumpPtr);const std::string package(packageChars.c_str(), packageChars.size());// 2 調(diào)用GraphicsStatsService.cpp里的addToDumpGraphicsStatsService::addToDump(dump, path, package, versionCode, startTime, endTime, data); } 復(fù)制代碼

2.4.1 剛才數(shù)據(jù)是按ProfileData這個(gè)結(jié)構(gòu)體大小讀的，現(xiàn)在將數(shù)據(jù)轉(zhuǎn)換成這個(gè)結(jié)構(gòu)。 2.4.2 調(diào)用native類的addToDump方法：

# GraphicsStatsService.cpp void GraphicsStatsService::addToDump(Dump* dump, const std::string& path, const std::string& package,int versionCode, int64_t startTime, int64_t endTime, const ProfileData* data) {//1 從指定路徑讀數(shù)據(jù)service::GraphicsStatsProto statsProto;if (!path.empty() && !parseFromFile(path, &statsProto)) {statsProto.Clear();}// 2 合并兩份數(shù)據(jù)if (data && !mergeProfileDataIntoProto(&statsProto, package, versionCode, startTime, endTime, data)) {return;}if (!statsProto.IsInitialized()) {ALOGW("Failed to load profile data from path '%s' and data %p",path.empty() ? "<empty>" : path.c_str(), data);return;}if (dump->type() == DumpType::Protobuf) {dump->proto().add_stats()->CopyFrom(statsProto);} else {// 3 打印數(shù)據(jù)，不需要protobuf格式dumpAsTextToFd(&statsProto, dump->fd());} } 復(fù)制代碼

2.4.2.a： 從指定路徑讀數(shù)據(jù)，為何還要讀呢，不是從共享內(nèi)存取的嗎？ 實(shí)際上數(shù)據(jù)在app死亡或者定時(shí)器到了時(shí)間，會(huì)調(diào)整數(shù)據(jù)，會(huì)將數(shù)據(jù)保存到data/system下的。下一篇討論數(shù)據(jù)來源。

bool GraphicsStatsService::parseFromFile(const std::string& path, service::GraphicsStatsProto* output) {...void* addr = mmap(nullptr, sb.st_size, PROT_READ, MAP_SHARED, fd, 0);...void* data = reinterpret_cast<uint8_t*>(addr) + sHeaderSize;int dataSize = sb.st_size - sHeaderSize;io::ArrayInputStream input{data, dataSize};bool success = output->ParseFromZeroCopyStream(&input);return success; } 復(fù)制代碼

核心是用protobuf的接口，將數(shù)據(jù)專成GraphicsStatsProto結(jié)構(gòu)。

2.4.2.b： merge數(shù)據(jù)，將兩份數(shù)據(jù)合并一下，大多數(shù)就是持久化在文件里的，跟內(nèi)存里的做加法。 2.4.2.c： dump數(shù)據(jù)：

void dumpAsTextToFd(service::GraphicsStatsProto* proto, int fd) {// This isn't a full validation, just enough that we can deref at willif (proto->package_name().empty() || !proto->has_summary()) {ALOGW("Skipping dump, invalid package_name() '%s' or summary %d",proto->package_name().c_str(), proto->has_summary());return;}dprintf(fd, "\nPackage: %s", proto->package_name().c_str());dprintf(fd, "\nVersion: %d", proto->version_code());dprintf(fd, "\nStats since: %lldns", proto->stats_start());dprintf(fd, "\nStats end: %lldns", proto->stats_end());auto summary = proto->summary();dprintf(fd, "\nTotal frames rendered: %d", summary.total_frames());dprintf(fd, "\nJanky frames: %d (%.2f%%)", summary.janky_frames(),(float) summary.janky_frames() / (float) summary.total_frames() * 100.0f);dprintf(fd, "\n50th percentile: %dms", findPercentile(proto, 50));dprintf(fd, "\n90th percentile: %dms", findPercentile(proto, 90));dprintf(fd, "\n95th percentile: %dms", findPercentile(proto, 95));dprintf(fd, "\n99th percentile: %dms", findPercentile(proto, 99));dprintf(fd, "\nNumber Missed Vsync: %d", summary.missed_vsync_count());dprintf(fd, "\nNumber High input latency: %d", summary.high_input_latency_count());dprintf(fd, "\nNumber Slow UI thread: %d", summary.slow_ui_thread_count());dprintf(fd, "\nNumber Slow bitmap uploads: %d", summary.slow_bitmap_upload_count());dprintf(fd, "\nNumber Slow issue draw commands: %d", summary.slow_draw_count());dprintf(fd, "\nHISTOGRAM:");for (const auto& it : proto->histogram()) {dprintf(fd, " %dms=%d", it.render_millis(), it.frame_count());}dprintf(fd, "\n"); } 復(fù)制代碼

至此，我們看到，將數(shù)據(jù)寫入到了從java傳過來的fd中，也是在Android dumpsys 實(shí)現(xiàn)一文中提到的，pipe創(chuàng)建的管道的寫入端。這樣結(jié)合dumpsys實(shí)現(xiàn)，看到了數(shù)據(jù)最終輸出到了終端。

下一篇討論數(shù)據(jù)來源。

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