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0134_Capture_ftrace_event.md

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Capture ftrace event

手动操作一下获取ftrace event并转换到kernelshark显示

参考文档

steps

  • apt-get install kernelshark
  • cd /sys/kernel/debug/
  • cat available_events | grep print 
    printk:console
  • cat events/printk/enable 
    0
  • echo "printk:console" > set_event
  • cat set_event 
    printk:console
  • cat events/printk/enable 
    1
  • echo > set_event_pid
  • echo > trace
  • echo 1 > tracing_on
  • cat trace 
    # tracer: nop
#
# entries-in-buffer/entries-written: 0/0   #P:4
#
#                              _-----=> irqs-off
#                             / _----=> need-resched
#                            | / _---=> hardirq/softirq
#                            || / _--=> preempt-depth
#                            ||| /     delay
#           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
#              | |       |   ||||       |         |
  • echo zengjf > trace_marker
  • cat trace 
    # tracer: nop
#
# entries-in-buffer/entries-written: 1/1   #P:4
#
#                              _-----=> irqs-off
#                             / _----=> need-resched
#                            | / _---=> hardirq/softirq
#                            || / _--=> preempt-depth
#                            ||| /     delay
#           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
#              | |       |   ||||       |         |
            bash-1122  [000] ....   214.838132: tracing_mark_write: zengjf
  • sudo trace-cmd extract
    • trace.dat
  • kernelshark
    下图中除了我自己输入的第一条，后面的是别的进程输出
    Capture_ftrace_event.png

trace-cmd采集数据原理

  • 采集所有CPU输出的Trace
    • /sys/kernel/debug/tracing/per_cpu/
      • cpu[x]
        • trace_pipe_raw
  • 将上面的CPU执行时输出的trace通过splice/pip/socket传输，socket接收到数据，然后解析到trace.dat中

KernelShark Build

  • wget https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/snapshot/trace-cmd-kernelshark-v1.0.tar.gz
  • tar xvf trace-cmd-kernelshark-v1.0.tar.gz
  • cd trace-cmd-kernelshark-v1.0
  • sudo apt-get install build-essential git cmake libjson-c-dev -y
  • sudo apt-get install freeglut3-dev libxmu-dev libxi-dev -y
  • sudo apt-get install qtbase5-dev -y
  • sudo apt-get install -y swig
  • make gui error 
    make[1]: '/home/pi/zengjf/trace-cmd-kernelshark-v1.0/lib/traceevent/libtraceevent.a' is up to date.
make[1]: '/home/pi/zengjf/trace-cmd-kernelshark-v1.0/lib/trace-cmd/libtracecmd.a' is up to date.
make[1]: 'ctracecmd.so' is up to date.
[ 22%] Built target kshark
[ 33%] Built target kshark-plot
[ 44%] Built target missed_events
[ 55%] Built target sched_events
[ 62%] Built target dfilter
[ 66%] Building CXX object examples/CMakeFiles/widgetdemo.dir/widgetdemo.cpp.o
/home/pi/zengjf/trace-cmd-kernelshark-v1.0/kernel-shark/examples/widgetdemo.cpp:16:10: fatal error: QtWidgets: No such file or directory
 #include <QtWidgets>
          ^~~~~~~~~~~
compilation terminated.
make[3]: *** [examples/CMakeFiles/widgetdemo.dir/build.make:63: examples/CMakeFiles/widgetdemo.dir/widgetdemo.cpp.o] Error 1
make[2]: *** [CMakeFiles/Makefile2:328: examples/CMakeFiles/widgetdemo.dir/all] Error 2
make[1]: *** [Makefile:130: all] Error 2
make: *** [Makefile:272: gui] Error 2
    • kernel-shark/CMakeLists.txt
      • 注释掉：add_subdirectory(${KS_DIR}/examples)
  • 最终编译出来的显示效果不好，时间轴不能正常显示