Android 埋点信息分析—

源码基于：Android U

0. 前言

在前一篇《Android statsd 埋点简析》一文中简单剖析了Android 埋点采集、传输的框架，本文在其基础对埋点信息进行解析，来看下Android 中埋下的内存信息有哪些。

1. 通过代码剖析google 埋点内容

1.1 PROCESS_MEMORY_STATE

frameworks/base/services/core/java/com/android/server/stats/pull/StatsPullAtomService.java

    int pullProcessMemoryStateLocked(int atomTag, List<StatsEvent> pulledData) {
        List<ProcessMemoryState> processMemoryStates =
                LocalServices.getService(ActivityManagerInternal.class)
                        .getMemoryStateForProcesses();
        for (ProcessMemoryState processMemoryState : processMemoryStates) {
            final MemoryStat memoryStat = readMemoryStatFromFilesystem(processMemoryState.uid,
                    processMemoryState.pid);
            if (memoryStat == null) {
                continue;
            }
            pulledData.add(FrameworkStatsLog.buildStatsEvent(atomTag, processMemoryState.uid,
                    processMemoryState.processName, processMemoryState.oomScore, memoryStat.pgfault,
                    memoryStat.pgmajfault, memoryStat.rssInBytes, memoryStat.cacheInBytes,
                    memoryStat.swapInBytes, -1 /*unused*/, -1 /*unused*/, -1 /*unused*/));
        }
        return StatsManager.PULL_SUCCESS;
    }

getMemoryStateForProcesses函数：读取每个应用进程；

readMemoryStatFromFilesystem函数：读取/proc/<pid>/stat节点，解析pgfault(9)、pgmajfault(11)、rssInbytes(23) 数据；

统计数据有：

uid
processName
oomScore
pgmajfault
rss
cache（memcg）
swap （memcg）

1.2 PROCESS_MEMORY_HIGH_WATER_MARK

    int pullProcessMemoryHighWaterMarkLocked(int atomTag, List<StatsEvent> pulledData) {
        List<ProcessMemoryState> managedProcessList =
                LocalServices.getService(ActivityManagerInternal.class)
                        .getMemoryStateForProcesses();
        for (ProcessMemoryState managedProcess : managedProcessList) {
            final MemorySnapshot snapshot = readMemorySnapshotFromProcfs(managedProcess.pid);
            if (snapshot == null) {
                continue;
            }
            pulledData.add(FrameworkStatsLog.buildStatsEvent(atomTag, managedProcess.uid,
                    managedProcess.processName,
                    // RSS high-water mark in bytes.
                    snapshot.rssHighWaterMarkInKilobytes * 1024L,
                    snapshot.rssHighWaterMarkInKilobytes));
        }
        // Complement the data with native system processes
        SparseArray<String> processCmdlines = getProcessCmdlines();
        managedProcessList.forEach(managedProcess -> processCmdlines.delete(managedProcess.pid));
        int size = processCmdlines.size();
        for (int i = 0; i < size; ++i) {
            ...
        }
        // Invoke rss_hwm_reset binary to reset RSS HWM counters for all processes.
        SystemProperties.set("sys.rss_hwm_reset.on", "1");
        return StatsManager.PULL_SUCCESS;
    }

该函数主要查询所有应用进程和native 进程的内存信息。

getMemoryStateForProcesses函数：读取每个应用进程；

readMemorySnapshotFromProcfs函数：读取/proc/<pid>/status节点，解析Uid、VmHWM、VmRss、RssAnon、RssShmem、VmSwap 数据。通过判定/proc/<pid>/status节点中是否有RssAnon、RssShmem、VmSwap数据排除 kernel 进程；

最后通过设置 prop 唤醒 rss_hwm_reset 程序，将VmHWM 清除。

统计数据有：

uid
processName / cmdline （native是cmdline）
VmHWM

1.3 PROCESS_MEMORY_SNAPSHOT

同上 HWM，统计每一个应用进程和native 进程的内存快照，区别在于这里另外统计了每个进程的 GPU 使用量：sys/fs/bpf/map_fpuMem_gpu_mem_total_map

统计数据有：

uid
processName / cmdline（native是cmdline）
pid
oomScore
rss
rss_anon
swap
rss_anon + swap
gpu memory
hasForegroundServices （native 为false）
rss_shmem

1.4 SYSTEM_ION_HEAP_SIZE

    int pullSystemIonHeapSizeLocked(int atomTag, List<StatsEvent> pulledData) {
        final long systemIonHeapSizeInBytes = readSystemIonHeapSizeFromDebugfs();
        pulledData.add(FrameworkStatsLog.buildStatsEvent(atomTag, systemIonHeapSizeInBytes));
        return StatsManager.PULL_SUCCESS;
    }

解析 sys/kernel/debug/ion/heaps/system 节点total 部分的数据。

1.5 ION_HEAP_SIZE

    int pullIonHeapSizeLocked(int atomTag, List<StatsEvent> pulledData) {
        int ionHeapSizeInKilobytes = (int) getIonHeapsSizeKb();
        pulledData.add(FrameworkStatsLog.buildStatsEvent(atomTag, ionHeapSizeInKilobytes));
        return StatsManager.PULL_SUCCESS;
    }

调用 Debug.getIonHeapsSizeKb，详细可以查看 android_os_Debug.cpp

解析/sys/kernel/ion/total_heaps_kb

1.6 PROCESS_SYSTEM_ION_HEAP_SIZE

    int pullProcessSystemIonHeapSizeLocked(int atomTag, List<StatsEvent> pulledData) {
        List<IonAllocations> result = readProcessSystemIonHeapSizesFromDebugfs();
        for (IonAllocations allocations : result) {
            pulledData.add(FrameworkStatsLog.buildStatsEvent(atomTag, getUidForPid(allocations.pid),
                    readCmdlineFromProcfs(allocations.pid),
                    (int) (allocations.totalSizeInBytes / 1024), allocations.count,
                    (int) (allocations.maxSizeInBytes / 1024)));
        }
        return StatsManager.PULL_SUCCESS;
    }

readProcessSystemIonHeapSizesFromDebugfs解析sys/kernel/debug/ion/heaps/system 节点进程部分数据。

1.7 PROCESS_DMABUF_MEMORY

    int pullProcessDmabufMemory(int atomTag, List<StatsEvent> pulledData) {
        KernelAllocationStats.ProcessDmabuf[] procBufs =
                KernelAllocationStats.getDmabufAllocations();

        if (procBufs == null) {
            return StatsManager.PULL_SKIP;
        }
        for (KernelAllocationStats.ProcessDmabuf procBuf : procBufs) {
            pulledData.add(FrameworkStatsLog.buildStatsEvent(
                    atomTag,
                    procBuf.uid,
                    procBuf.processName,
                    procBuf.oomScore,
                    procBuf.retainedSizeKb,
                    procBuf.retainedBuffersCount,
                    0, /* mapped_dmabuf_kb - deprecated */
                    0, /* mapped_dmabuf_count - deprecated */
                    procBuf.surfaceFlingerSizeKb,
                    procBuf.surfaceFlingerCount
            ));
        }
        return StatsManager.PULL_SUCCESS;
    }

getDmabufAllocations函数主要是调用 dmabufinfo.cpp 中ReadProcfsDmaBufs函数获取进程dmabuf 信息。

统计数据有：

uid
cmdline
oomScore
total (KB)
inode count
surfaceflinger size （KB）
surfaceflinger inode cnt

1.8 SYSTEM_MEMORY

    int pullSystemMemory(int atomTag, List<StatsEvent> pulledData) {
        SystemMemoryUtil.Metrics metrics = SystemMemoryUtil.getMetrics();
        pulledData.add(
                FrameworkStatsLog.buildStatsEvent(
                        atomTag,
                        metrics.unreclaimableSlabKb,           //meminfo.SUnreclaim
                        metrics.vmallocUsedKb,                 //meminfo.VmallocUsed
                        metrics.pageTablesKb,                  //meminfo.PageTables
                        metrics.kernelStackKb,                 //meminfo.KernelStack
                        metrics.totalIonKb,
                        metrics.unaccountedKb,
                        metrics.gpuTotalUsageKb,
                        metrics.gpuPrivateAllocationsKb,
                        metrics.dmaBufTotalExportedKb,
                        metrics.shmemKb,                       //meminfo.Shmem
                        metrics.totalKb,                       //meminfo.MemTotal
                        metrics.freeKb,                        //meminfo.MemFree
                        metrics.availableKb,                   //meminfo.MemAvailable
                        metrics.activeKb,                      //meminfo.Active
                        metrics.inactiveKb,                    //meminfo.Inactive
                        metrics.activeAnonKb,                  //meminfo.Active(anon)
                        metrics.inactiveAnonKb,                //meminfo.Inactive(anon)
                        metrics.activeFileKb,                  //meminfo.Active(file)
                        metrics.inactiveFileKb,                //meminfo.Inactive(file)
                        metrics.swapTotalKb,                   //meminfo.SwapTotal
                        metrics.swapFreeKb,                    //meminfo.SwapFree
                        metrics.cmaTotalKb,                    //meminfo.CmaTotal
                        metrics.cmaFreeKb));                   //meminfo.CmaFree
        return StatsManager.PULL_SUCCESS;
    }

totalIonKb：统计/sys/kernel/dmabuf/buffers下所有定义在 /dev/dma_heap 的 exporter的总大小；如果不支持dmabuf，那就统计/sys/kernel/ion/total_heaps_kb节点；

gpuTotalUsageKb：解析节点 /sys/fs/bpf/map_gpuMem_gpu_mem_total_map

gpuPrivateAllocationsKb：获取GPU private

dmaBufTotalExportedKb：统计/sys/kernel/dmabuf/buffers下dmabuf 总和；

unaccountedKb：meminfo.MemTotal - accountedKb;

accountedKb 包括：

meminfo.MemFree + zram + meminfo.Buffers + meminfo.active + meminfo.inactive + meminfo.Unevictable + meminfo.SUnreclaim + meminfo.KReclaimable + meminfo.VmallocUsed + meminfo.PageTables + meminfo.KernelStack + dmaBufTotalExportedKb + gpuPrivateAllocationsKb

1.9 VMSTAT

    int pullVmStat(int atomTag, List<StatsEvent> pulledData) {
        ProcfsMemoryUtil.VmStat vmStat = ProcfsMemoryUtil.readVmStat();
        if (vmStat != null) {
            pulledData.add(
                    FrameworkStatsLog.buildStatsEvent(
                            atomTag,
                            vmStat.oomKillCount));
        }
        return StatsManager.PULL_SUCCESS;
    }

只统计 oom_kill 的次数。