•  28-06-2023
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سؤال

I know this is asked before but I am afraid "systrace uses atrace which extends ftrace, so check ftrace format here" is not enough for me. I am after more details on some systrace specific tag/formats. I have some guesses which I have little confidence on, thus I need somebody who really KNOW them to confirm/disconfirm.

Here is some results I found in trace.html. 

# tracer: nop\n\
#\n\
# entries-in-buffer/entries-written: 393636/393636   #P:1\n\
#\n\
#                              _-----=> irqs-off\n\
#                             / _----=> need-resched\n\
#                            | / _---=> hardirq/softirq\n\
#                            || / _--=> preempt-depth\n\
#                            ||| /     delay\n\
#           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION\n\
#              | |       |   ||||       |         |\n\
          atrace-27768 [000] ...2 17184.509740: sched_switch: prev_comm=atrace prev_pid=27768 prev_prio=120 prev_state=S ==> next_comm=swapper/0 next_pid=0 next_prio=120\n\
      Thread-117-16753 [001] ...1 17184.510251: tracing_mark_write: B|4237|eglSwapBuffers\n\
          <idle>-0     [000] d.h4 17184.510329: sched_wakeup: comm=AudioOut_2 pid=608 prio=101 success=1 target_cpu=000\n\
          <idle>-0     [000] ...2 17184.510338: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=AudioOut_2 next_pid=608 next_prio=101\n\
      AudioOut_2-608   [000] d..4 17184.510393: sched_wakeup: comm=AudioTrack pid=16778 prio=104 success=1 target_cpu=000\n\
      AudioOut_2-608   [000] ...2 17184.510446: sched_switch: prev_comm=AudioOut_2 prev_pid=608 prev_prio=101 prev_state=S ==> next_comm=AudioTrack next_pid=16778 next_prio=104\n\
      Thread-117-16753 [001] ...1 17184.510610: tracing_mark_write: B|4237|queueBuffer\n\
      Thread-117-16753 [001] d..4 17184.510648: sched_wakeup: comm=Binder_2 pid=189 prio=120 success=1 target_cpu=001\n\
      Thread-117-16753 [001] ...2 17184.510656: sched_switch: prev_comm=Thread-117 prev_pid=16753 prev_prio=120 prev_state=R+ ==> next_comm=Binder_2 next_pid=189 next_prio=120\n\
        Binder_2-189   [001] ...2 17184.510664: sched_switch: prev_comm=Binder_2 prev_pid=189 prev_prio=120 prev_state=D ==> next_comm=Thread-117 next_pid=16753 next_prio=120\n\
      Thread-117-16753 [001] d..4 17184.510670: sched_wakeup: comm=Binder_2 pid=189 prio=120 success=1 target_cpu=001\n\
      Thread-117-16753 [001] ...2 17184.510673: sched_switch: prev_comm=Thread-117 prev_pid=16753 prev_prio=120 prev_state=R+ ==> next_comm=Binder_2 next_pid=189 next_prio=120\n\
        Binder_2-189   [001] ...1 17184.510722: tracing_mark_write: B|147|queueBuffer\n\
        Binder_2-189   [001] ...1 17184.510729: tracing_mark_write: B|147|SurfaceView: 0\n\
        Binder_2-189   [001] ...1 17184.510734: tracing_mark_write: E\n\
        Binder_2-189   [001] ...1 17184.510753: tracing_mark_write: C|147|SurfaceView|1\n\
        Binder_2-189   [001] d..4 17184.510772: sched_wakeup: comm=EventThread pid=255 prio=111 success=1 target_cpu=001\n\
        Binder_2-189   [001] ...1 17184.510781: tracing_mark_write: E\n\
        Binder_2-189   [001] ...2 17184.510810: sched_switch: prev_comm=Binder_2 prev_pid=189 prev_prio=120 prev_state=S ==> next_comm=EventThread next_pid=255 next_prio=111\n\
     EventThread-255   [001] d..4 17184.510828: sched_wakeup: comm=DispSync pid=186 prio=111 success=1 target_cpu=001\n\
     EventThread-255   [001] ...1 17184.510840: tracing_mark_write: C|147|VsyncOn|1\n\
     EventThread-255   [001] ...2 17184.510852: sched_switch: prev_comm=EventThread prev_pid=255 prev_prio=111 prev_state=S ==> next_comm=DispSync next_pid=186 next_prio=111\n\
        DispSync-186   [001] ...2 17184.510867: sched_switch: prev_comm=DispSync prev_pid=186 prev_prio=111 prev_state=S ==> next_comm=Thread-117 next_pid=16753 next_prio=120\n\
      Thread-117-16753 [001] ...1 17184.510885: tracing_mark_write: E\n\
      Thread-117-16753 [001] ...1 17184.510893: tracing_mark_write: B|4237|query\n\
      Thread-117-16753 [001] ...1 17184.510899: tracing_mark_write: E\n\
      Thread-117-16753 [001] ...1 17184.510906: tracing_mark_write: B|4237|query\n\
      Thread-117-16753 [001] ...1 17184.510911: tracing_mark_write: E\n\
      Thread-117-16753 [001] ...1 17184.510924: tracing_mark_write: E\n\
      AudioTrack-16778 [000] d.h7 17184.510984: sched_wakeup: comm=FastMixer pid=330 prio=96 success=1 target_cpu=000\n\
      AudioTrack-16778 [000] ...2 17184.511000: sched_switch: prev_comm=AudioTrack prev_pid=16778 prev_prio=104 prev_state=R+ ==> next_comm=FastMixer next_pid=330 next_prio=96\n\
      Thread-117-16753 [001] ...1 17184.511012: tracing_mark_write: B|4237|dequeueBuffer\n\
      Thread-117-16753 [001] d..4 17184.511034: sched_wakeup: comm=Binder_1 pid=185 prio=120 success=1 target_cpu=001\n\
      Thread-117-16753 [001] ...2 17184.511041: sched_switch: prev_comm=Thread-117 prev_pid=16753 prev_prio=120 prev_state=R+ ==> next_comm=Binder_1 next_pid=185 next_prio=120\n\
        Binder_1-185   [001] ...2 17184.511053: sched_switch: prev_comm=Binder_1 prev_pid=185 prev_prio=120 prev_state=D ==> next_comm=Thread-117 next_pid=16753 next_prio=120\n\
      Thread-117-16753 [001] d..4 17184.511059: sched_wakeup: comm=Binder_1 pid=185 prio=120 success=1 target_cpu=001\n\
      Thread-117-16753 [001] ...2 17184.511062: sched_switch: prev_comm=Thread-117 prev_pid=16753 prev_prio=120 prev_state=R+ ==> next_comm=Binder_1 next_pid=185 next_prio=120\n\
       FastMixer-330   [000] ...2 17184.511070: sched_switch: prev_comm=FastMixer prev_pid=330 prev_prio=96 prev_state=S ==> next_comm=AudioTrack next_pid=16778 next_prio=104\n\
      AudioTrack-16778 [000] ...2 17184.511087: sched_switch: prev_comm=AudioTrack prev_pid=16778 prev_prio=104 prev_state=S ==> next_comm=swapper/0 next_pid=0 next_prio=120\n\
        Binder_1-185   [001] ...1 17184.511093: tracing_mark_write: B|147|dequeueBuffer\n\
        Binder_1-185   [001] ...1 17184.511102: tracing_mark_write: B|147|SurfaceView: 1\n\
        Binder_1-185   [001] ...1 17184.511105: tracing_mark_write: E\n\
        Binder_1-185   [001] ...1 17184.511110: tracing_mark_write: E\n\
        Binder_1-185   [001] ...2 17184.511131: sched_switch: prev_comm=Binder_1 prev_pid=185 prev_prio=120 prev_state=S ==> next_comm=Thread-117 next_pid=16753 next_prio=120\n\
      Thread-117-16753 [001] ...1 17184.511143: tracing_mark_write: E\n\
          <idle>-0     [000] d.h4 17184.512011: sched_wakeup: comm=Thread-117 pid=16780 prio=120 success=1 target_cpu=000\n\
          <idle>-0     [000] ...2 17184.512021: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=Thread-117 next_pid=16780 next_prio=120\n\
      Thread-117-16780 [000] ...2 17184.512047: sched_switch: prev_comm=Thread-117 prev_pid=16780 prev_prio=120 prev_state=S ==> next_comm=swapper/0 next_pid=0 next_prio=120\n\
          <idle>-0     [000] d.h4 17184.513414: sched_wakeup: comm=Thread-117 pid=17201 prio=120 success=1 target_cpu=000\n\
          <idle>-0     [000] ...2 17184.513425: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=Thread-117 next_pid=17201 next_prio=120\n\
      Thread-117-17201 [000] ...2 17184.513441: sched_switch: prev_comm=Thread-117 prev_pid=17201 prev_prio=120 prev_state=S ==> next_comm=swapper/0 next_pid=0 next_prio=120\n\
      Thread-117-16753 [001] ...2 17184.516369: sched_switch: prev_comm=Thread-117 prev_pid=16753 prev_prio=120 prev_state=S ==> next_comm=swapper/1 next_pid=0 next_prio=120\n\
          <idle>-0     [000] d.h6 17184.517936: sched_wakeup: comm=kworker/0:3 pid=27267 prio=120 success=1 target_cpu=000\n\
          <idle>-0     [000] ...2 17184.517947: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=kworker/0:3 next_pid=27267 next_prio=120\n\
     kworker/0:3-27267 [000] ...2 17184.518045: sched_switch: prev_comm=kworker/0:3 prev_pid=27267 prev_prio=120 prev_state=S ==> next_comm=swapper/0 next_pid=0 next_prio=120\n\
          <idle>-0     [000] d.h7 17184.520977: sched_wakeup: comm=FastMixer pid=330 prio=96 success=1 target_cpu=000\n\
          <idle>-0     [000] ...2 17184.520986: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=FastMixer next_pid=330 next_prio=96\n\
       FastMixer-330   [000] ...2 17184.521041: sched_switch: prev_comm=FastMixer prev_pid=330 prev_prio=96 prev_state=S ==> next_comm=swapper/0 next_pid=0 next_prio=120\n\
          <idle>-0     [000] d.h6 17184.521117: sched_wakeup: comm=kworker/0:3 pid=27267 prio=120 success=1 target_cpu=000\n\
          <idle>-0     [000] ...2 17184.521122: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=kworker/0:3 next_pid=27267 next_prio=120\n\
     kworker/0:3-27267 [000] d..4 17184.521130: sched_wakeup: comm=hwc_eventmon pid=246 prio=100 success=1 target_cpu=000\n\
     kworker/0:3-27267 [000] ...2 17184.521135: sched_switch: prev_comm=kworker/0:3 prev_pid=27267 prev_prio=120 prev_state=S ==> next_comm=hwc_eventmon next_pid=246 next_prio=100\n\
    hwc_eventmon-246   [000] ...2 17184.521155: sched_switch: prev_comm=hwc_eventmon prev_pid=246 prev_prio=100 prev_state=S ==> next_comm=swapper/0 next_pid=0 next_prio=120\n\
          <idle>-0     [000] d.s5 17184.521414: sched_wakeup: comm=cfinteractive pid=88 prio=0 success=1 target_cpu=000\n\
          <idle>-0     [000] ...2 17184.521420: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=cfinteractive next_pid=88 next_prio=0\n\
   cfinteractive-88    [000] ...2 17184.521440: sched_switch: prev_comm=cfinteractive prev_pid=88 prev_prio=0 prev_state=S ==> next_comm=swapper/0 next_pid=0 next_prio=120\n\
          <idle>-0     [001] d.h4 17184.525814: sched_wakeup: comm=DispSync pid=186 prio=111 success=1 target_cpu=001\n\
          <idle>-0     [001] ...2 17184.525821: sched_switch: prev_comm=swapper/1 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=DispSync next_pid=186 next_prio=111\n\
        DispSync-186   [001] d..4 17184.525842: sched_wakeup: comm=EventThread pid=255 prio=111 success=1 target_cpu=001\n\
        DispSync-186   [001] ...2 17184.525851: sched_switch: prev_comm=DispSync prev_pid=186 prev_prio=111 prev_state=S ==> next_comm=EventThread next_pid=255 next_prio=111\n\
          <idle>-0     [000] d.h3 17184.525884: sched_wakeup: comm=surfaceflinger pid=147 prio=112 success=1 target_cpu=000\n\
          <idle>-0     [000] ...2 17184.525890: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=surfaceflinger next_pid=147 next_prio=112\n\
     EventThread-255   [001] ...2 17184.525892: sched_switch: prev_comm=EventThread prev_pid=255 prev_prio=111 prev_state=S ==> next_comm=swapper/1 next_pid=0 next_prio=120\n\

Q1: Why does a "thread" come with different PID and sometimes get scheduled to run on different CPUs simultaneously, e.g. Thread-117? What does "thread" really mean here?

        Binder_1-185   [001] ...2 17184.511131: sched_switch: prev_comm=Binder_1 prev_pid=185 prev_prio=120 prev_state=S ==> next_comm=Thread-117 next_pid=16753 next_prio=120\n\
      Thread-117-16753 [001] ...1 17184.511143: tracing_mark_write: E\n\
          <idle>-0     [000] d.h4 17184.512011: sched_wakeup: comm=Thread-117 pid=16780 prio=120 success=1 target_cpu=000\n\
          <idle>-0     [000] ...2 17184.512021: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=Thread-117 next_pid=16780 next_prio=120\n\
      Thread-117-16780 [000] ...2 17184.512047: sched_switch: prev_comm=Thread-117 prev_pid=16780 prev_prio=120 prev_state=S ==> next_comm=swapper/0 next_pid=0 next_prio=120\n\

Q2: What does "prev_state" in "sched_switch" mean? What does "S,D,R,R+" refer to in this variable respectively?

Q3: "tracing_mark_write" uses B for begin, C for change and E for end. But E tag does not come with trace name. How to determine which B tag it corresponds to? Does it work in a call stack style LIFO? If so, that can only be guaranteed if a "thread" is a real thread that can not be split to run on two CPUs coherently. Which lead us back to Q1.

Any help is appreciated!

هل كانت مفيدة؟

المحلول

A1: It's showing you the thread name that you would see from ps -t on the device, which is set by the process. Unnamed Dalvik threads are named "Thread-N", where N is a serial number tracked by the Thread class (the same way the Binder thread pool created "Binder_1"). So the "117" in "Thread-117" has no relationship to the system pid or tid; it's just what the thread is called. It's not guaranteed to be unique -- you could have multiple instances in one process, or in separate processes.

A2: The states are the same as you'd see in ps output. See the Linux man page's "PROCESS STATE CODES" section:

   D    uninterruptible sleep (usually IO)
   R    running or runnable (on run queue)
   S    interruptible sleep (waiting for an event to complete)
   ...

A3: Yes, LIFO, for a single thread. This is matched by the public android.os.Trace API. (There is a different (non-public) API for "asynchronous" traces where you supply the same tag and "cookie" for start and end, but it's not used as widely.)

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