Forums - Profiling native library

Hi Tony,

Snapdragon Profiler doesn't have that feature currently although we are working towards that kind of functionality. That said, as a temporary workaround you could write generically formatted data to the android trace marker event, Snapdragon Profiler will be able to recognize it and show the desired data along side your trace captures. This can be achieved by directly writing formatted strings  to /sys/kernel/debug/tracing/trace_marker with the "tracing_mark_write" format. I'd recommend reading on the format as it supports various types of events (most notably 'C' counter type data and 'B/E' begin/end range markers). Note that this wont give you the statistical information you desire right off the bat so it might require some post processing on your side to get the most used range markers, etc. 

Hi Tony,

I recently was faced with the same issue and have discovered a wonderful work around.  First Carlos is absolutely right, one needs to write to write to the system trace file at the path he gave.  However, there's one unfortunate caveot, not all production devices have systrace support. The file might not exist on your device; if you're in this case, you're probably on a non N device this should sort you out:

*/

mount -o rw,remount -t debugfs none /sys/kernel/debug

If that doesn't work and the file still doesn't exist, you have a rooting/rebuilding kernel with systrace enabled enjoyable experience in your future.

Here's the Java version: https://developer.android.com/studio/profile/systrace.html, there is a NDK version that only works in N+ (ATrace_BeginSection/ATrace_EndSection) but it also only handles the b/e markers that weren't enough for my needs; and very likely wont help you with yours.  The reason why is the B/E section only takes a pid so any end event on any thread in the same pid has the fun side effect of making the nested section tags pretty worthless in most apps.

There's two other types of markers, an async marker 'S'/'F' which you provide the pid and a cookie so it can correctly handle a begin/end along with a 'C' marker that will give you a count.  The count is interesting in that it will render out a nice bar graph (useful for displaying variable data).

Now for the reason for posting this, the Snapdragon Profiler is better at displaying the resulting html files.  It also has an import trace file utility.  The problem that it solves is that the Async tags will display as disjoint items in the html page; when there's a lot of them, it's hard to sift through it.  Snapdragon Profiler will put them in one async tab that you can drill into and find the big outliers.  It's admittedly not ideal and you have to pick and chose your battles carefully as too many 

So what I do is hook up the command line trace file generation tool to our CI / auto unit testing system and use Snapdragon Profiler to view the results, when things go bump; this provides a good way to understand when it went bump.

Here's some example code that works pretty well:

int fileId = open("/sys/kernel/tracing/trace_marker", O_WRONLY);
if(fileId == -1) assert(false);

void nested_begin(const char* markerName) {
   char buf[256];
   int len = sprintf(buf, 256, "B|%d|%s", getpid(), markerName);
   write(fileId, buf, len); 
}

//I'm skipping the rest of the non relevant parts and showing the strings that are possible and what they go with:
void nested_end(){
  int len = sprintf(buf, 256, "E");
}

void counter(const char* counterName, int value) {
     int len = sprintf(buf, 256, "C|%d|%s|%d", getpid(), counterName, value);
}

void async_begin(const char* markerName, int cookie) {
       int len = sprintf(buf, 256, "S|%d|%s|%i", getpid(), markerName, cookie);
}

void async_end(const char* markerName, int cookie) {
      int len = sprintf(buf, 256, "F|%d|%s|%i", getpid(), markerName, cookie);
}

Note that you can't use | in any of your character strings or bad things happen.