OpenHarmony 在DevEco环境中开发Native C++时使用HiTrace

摘要

本文讲述在DevEco环境中如何在Native C++开发时使用HiTrace，包括代码写法及Trace捕捉。

代码写法

在C++中使用HiTrace，需要引入头文件 <hitrace/trace.h>, 并在 CMakeLists.txt中链接上HiTrace库，如下图所示：

# Others settings
find_library(
    # Sets the name of the path variable.
    hitrace-lib
    # Specifies the name of the NDK library that
    # you want CMake to locate.
    hitrace_ndk.z
    #libhitrace_ndk.z
)
target_link_libraries(nativecode PUBLIC
    # Other used libraries
    ${hitrace-lib}
)

若出现头文件或库文件找不到的情况，则参考此篇博文

Trace捕捉

Trace捕捉有三种方法：

1. 通过 hdc shell运行 bytrace命令
2. 通过DevEco自带的Profiler
3. 通过OHOS中自带的SmarPerf App

笔者偏爱方法1，不喜欢用方法2和3，因为这俩操作很麻烦。

bytrace命令的参数选项解释如下，详情参考官方链接

Option	Description
-h, --help	Views the help text for bytrace.
-bn, --buffer_size n	Sets the size of the buffer (KB) for storing and reading traces. The default buffer size is 2048 KB.
-tn, --time n	Sets the bytrace uptime in seconds, which depends on the time required for analysis.
--trace_clockclock	Sets the type of the clock for adding a timestamp to a trace, which can beboot (default), global, mono, uptime, or perf.
--trace_begin	Starts capturing traces.
--trace_dump	Dumps traces to a specified position (console where you run this command by default).
--trace_finish	Stops capturing traces and dumps traces to a specified position (console where you run this command by default).
-l, --list_categories	Lists the bytrace categories supported by the device.
--overwrite	Sets the action to take when the buffer is full. If this option is used, the latest traces are discarded; if this option is not used, the earliest traces are discarded (default).
-ofilename, --output filename	Outputs traces to a specified file.
-z	Compresses a captured trace

但是，官方链接里给出trace的命令示例不好使，因为官方示例中把trace导出到了没有写权限的地方(在DAYU200上测得)。所以这里给出一个 bytrace命令参考：

bytrace -b <buffer_size> -t <持续时间> --overwrite [<category1>,<category2>,...] > /data/local/tmp/mytrace.ftrace

其中，可用的 category可通过如下命令获取：

bytrace --list_categories

我一般常用的命令如下：

# Run in PC terminal
hdc shell "bytrace -b 163840 -t 10 --overwrite ability graphic binder app ace freq idle sched misc multimodalinput ohos sync > /data/local/tmp/mytrace.ftrace";hdc file recv /data/local/tmp/mytrace.ftrace <PATH_ON_PC>

mytrace.ftrace的查看可使用https://ui.perfetto.dev/

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