[Android systrace系列] systrace的信息从哪里来
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这篇文章的小目标：
1. systrace是怎么抓出来的
2. 这些信息的来源是什么
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[Android systrace系列] systrace入门第一式 介绍了用命令行抓取systrace的方法。
打开systrace.py的目录，会发现一大堆python文件，让人以为抓取systrace的流程很复杂。
其实不然，systrace是附属于catapult这个项目（传送门），是一个抓trace的框架，而且不仅仅为Andorid服务。
打开/catapult/systrace/systrace/tracing_agents，我们就能发现很多抓trace的agent，这是抓不同类型信息对应的代码逻辑。
抓Android默认用到这三个agent，对应三类信息：
atrace_agent（atrace，负责收集用户空间打印的systrace log和kernel ftrace事件）
android_process_data_agent（ps命令，用来对应进程名与PID）
android_cgroup_agent（cgroup中cpuset子系统，市面销售的机器不一定能抓到）
atrace抓取的信息是Android systrace中最核心的部分。
通过atrace_agent.py的函数StartAgentTracing和StopAgentTracing，我们终于知道了systrace的主要部分是通过atrace命令抓取的。
实质上，只抓取atrace就可以生成systrace html文件了。
虽然使用systrace.py是抓取systrace最常规的方法，但如果要在测试脚本加入抓systrace的操作，我认为atrace命令是最直接的方法，也可以节省测试脚本的运行时间。
这也有助于了解systrace的细节，衍生出更多技巧。
0. 执行adb shell atrace --list_categories，选择你需要的log类别
1. adb shell atrace --async_start -b 8192 gfx input view webview wm am sm audio video camera hal res dalvik rs bionic power pm ss database network sched freq idle disk sync memreclaim binder_driver binder_lock gfx ion
2. 重现问题，现象出现后，执行 adb shell atrace --async_stop -z > a.out
3. 事后转换成html文件，systrace.py --from-file a.out -o a.html
现在我们阅读atrace的代码，寻找更多细节。
代码路径：//android/frameworks/native/cmds/atrace/atrace.cpp
这个数组，就是之前提到的systrace信息的两大来源，用户空间打印的systrace log和kernel ftrace事件。
用户空间systrace log：ATRACE_TAG 开头的
kernel ftrace：events开头的
static const TracingCategory k_categories[] = { { "gfx", "Graphics", ATRACE_TAG_GRAPHICS, { { OPT, "events/mdss/enable" }, { OPT, "events/sde/enable" }, } }, { "input", "Input", ATRACE_TAG_INPUT, { } }, { "view", "View System", ATRACE_TAG_VIEW, { } }, { "webview", "WebView", ATRACE_TAG_WEBVIEW, { } }, { "wm", "Window Manager", ATRACE_TAG_WINDOW_MANAGER, { } }, { "am", "Activity Manager", ATRACE_TAG_ACTIVITY_MANAGER, { } }, { "sm", "Sync Manager", ATRACE_TAG_SYNC_MANAGER, { } }, { "audio", "Audio", ATRACE_TAG_AUDIO, { } }, { "video", "Video", ATRACE_TAG_VIDEO, { } }, { "camera", "Camera", ATRACE_TAG_CAMERA, { } }, { "hal", "Hardware Modules", ATRACE_TAG_HAL, { } }, { "res", "Resource Loading", ATRACE_TAG_RESOURCES, { } }, { "dalvik", "Dalvik VM", ATRACE_TAG_DALVIK, { } }, { "rs", "RenderScript", ATRACE_TAG_RS, { } }, { "bionic", "Bionic C Library", ATRACE_TAG_BIONIC, { } }, { "power", "Power Management", ATRACE_TAG_POWER, { } }, { "pm", "Package Manager", ATRACE_TAG_PACKAGE_MANAGER, { } }, { "ss", "System Server", ATRACE_TAG_SYSTEM_SERVER, { } }, { "database", "Database", ATRACE_TAG_DATABASE, { } }, { "network", "Network", ATRACE_TAG_NETWORK, { } }, { "adb", "ADB", ATRACE_TAG_ADB, { } }, { "vibrator", "Vibrator", ATRACE_TAG_VIBRATOR, { } }, { "aidl", "AIDL calls", ATRACE_TAG_AIDL, { } }, { k_coreServiceCategory, "Core services", 0, { } }, { k_pdxServiceCategory, "PDX services", 0, { } }, { "sched", "CPU Scheduling", 0, { { REQ, "events/sched/sched_switch/enable" }, { REQ, "events/sched/sched_wakeup/enable" }, { OPT, "events/sched/sched_waking/enable" }, { OPT, "events/sched/sched_blocked_reason/enable" }, { OPT, "events/sched/sched_cpu_hotplug/enable" }, { OPT, "events/sched/sched_pi_setprio/enable" }, { OPT, "events/cgroup/enable" }, } }, { "irq", "IRQ Events", 0, { { REQ, "events/irq/enable" }, { OPT, "events/ipi/enable" }, } }, { "irqoff", "IRQ-disabled code section tracing", 0, { { REQ, "events/preemptirq/irq_enable/enable" }, { REQ, "events/preemptirq/irq_disable/enable" }, } }, { "preemptoff", "Preempt-disabled code section tracing", 0, { { REQ, "events/preemptirq/preempt_enable/enable" }, { REQ, "events/preemptirq/preempt_disable/enable" }, } }, { "i2c", "I2C Events", 0, { { REQ, "events/i2c/enable" }, { REQ, "events/i2c/i2c_read/enable" }, { REQ, "events/i2c/i2c_write/enable" }, { REQ, "events/i2c/i2c_result/enable" }, { REQ, "events/i2c/i2c_reply/enable" }, { OPT, "events/i2c/smbus_read/enable" }, { OPT, "events/i2c/smbus_write/enable" }, { OPT, "events/i2c/smbus_result/enable" }, { OPT, "events/i2c/smbus_reply/enable" }, } }, { "freq", "CPU Frequency", 0, { { REQ, "events/power/cpu_frequency/enable" }, { OPT, "events/power/clock_set_rate/enable" }, { OPT, "events/power/clock_disable/enable" }, { OPT, "events/power/clock_enable/enable" }, { OPT, "events/clk/clk_set_rate/enable" }, { OPT, "events/clk/clk_disable/enable" }, { OPT, "events/clk/clk_enable/enable" }, { OPT, "events/power/cpu_frequency_limits/enable" }, } }, { "membus", "Memory Bus Utilization", 0, { { REQ, "events/memory_bus/enable" }, } }, { "idle", "CPU Idle", 0, { { REQ, "events/power/cpu_idle/enable" }, } }, { "disk", "Disk I/O", 0, { { OPT, "events/f2fs/f2fs_sync_file_enter/enable" }, { OPT, "events/f2fs/f2fs_sync_file_exit/enable" }, { OPT, "events/f2fs/f2fs_write_begin/enable" }, { OPT, "events/f2fs/f2fs_write_end/enable" }, { OPT, "events/ext4/ext4_da_write_begin/enable" }, { OPT, "events/ext4/ext4_da_write_end/enable" }, { OPT, "events/ext4/ext4_sync_file_enter/enable" }, { OPT, "events/ext4/ext4_sync_file_exit/enable" }, { REQ, "events/block/block_rq_issue/enable" }, { REQ, "events/block/block_rq_complete/enable" }, } }, { "mmc", "eMMC commands", 0, { { REQ, "events/mmc/enable" }, } }, { "load", "CPU Load", 0, { { REQ, "events/cpufreq_interactive/enable" }, } }, { "sync", "Synchronization", 0, { // before linux kernel 4.9 { OPT, "events/sync/enable" }, // starting in linux kernel 4.9 { OPT, "events/fence/enable" }, } }, { "workq", "Kernel Workqueues", 0, { { REQ, "events/workqueue/enable" }, } }, { "memreclaim", "Kernel Memory Reclaim", 0, { { REQ, "events/vmscan/mm_vmscan_direct_reclaim_begin/enable" }, { REQ, "events/vmscan/mm_vmscan_direct_reclaim_end/enable" }, { REQ, "events/vmscan/mm_vmscan_kswapd_wake/enable" }, { REQ, "events/vmscan/mm_vmscan_kswapd_sleep/enable" }, { OPT, "events/lowmemorykiller/enable" }, } }, { "regulators", "Voltage and Current Regulators", 0, { { REQ, "events/regulator/enable" }, } }, { "binder_driver", "Binder Kernel driver", 0, { { REQ, "events/binder/binder_transaction/enable" }, { REQ, "events/binder/binder_transaction_received/enable" }, { OPT, "events/binder/binder_set_priority/enable" }, } }, { "binder_lock", "Binder global lock trace", 0, { { OPT, "events/binder/binder_lock/enable" }, { OPT, "events/binder/binder_locked/enable" }, { OPT, "events/binder/binder_unlock/enable" }, } }, { "pagecache", "Page cache", 0, { { REQ, "events/filemap/enable" }, } }, };
各个ATRACE_TAG_XXX的功能是掩码，在 //android/system/core/include/cutils/trace.h 的函数
static inline void atrace_begin(uint64_t tag, const char* name) 中控制是否写入相应TAG的log。
systrace在各层的调用接口，以及最终systrace的log格式如下表：
（看不清楚的可以右击图片，在新标签页打开图片）
跟踪上表的代码很容易会发现，用户空间的systrace log，最终通过libcutils的接口，写入到
手机的 /sys/kernel/debug/tracing/trace_marker，就是写入到kernel ftrace的buffer中。
用户空间打印的systrace log 和 kernel ftrace事件在这里胜利会师了。
用纯文本打开systrace html 文件，除了上述两类log，开头还有一大段Javascript。
通过Javascript的解析处理，呈现出systrace可视化的分析界面。
转载请注明出处：https://www.cnblogs.com/zzcperf/p/14052681.html
