On Wed, 15 May 2013 23:21:39 +0200, Jiri Olsa wrote: > On Tue, May 14, 2013 at 07:13:53PM +0900, Namhyung Kim wrote: >> From: Namhyung Kim <namhyung....@lge.com> >> >> The ftrace record command is for saving raw ftrace buffer contents >> which can be get from per_cpu/cpuX/trace_pipe_raw. >> >> Since ftrace events are generated very frequently so single thread for >> recording mostly resulted in buffer overruns. Thus it uses per-cpu >> recorder thread to prevent such cases and they save the contents to >> their own files. >> >> These per-cpu data files are saved in a directory so that they can be >> easily found when needed. I chose the default directory name as >> "perf.data.dir" and the first two (i.e. "perf.data") can be changed >> with -o option. The structure of the directory looks like: >> >> $ tree perf.data.dir >> perf.data.dir/ >> |-- perf.header >> |-- trace-cpu0.buf >> |-- trace-cpu1.buf >> |-- trace-cpu2.buf >> `-- trace-cpu3.buf >> >> In addition to trace-cpuX.buf files, it has perf.header file also. >> The perf.header file is compatible with existing perf.data format and >> contains usual event information, feature mask and sample data. The >> sample data is synthesized to indicate given cpu has a record file. > > so AFAICS we store sample event for each cpu we recorded (in record > command) and by processing those samples (show/report) we get data > files names for each cpu
Correct. > > hum, I might have missed some discussion about this, but seems > like header feature fits better for this, as long as we store > only cpus.. FTRACE_CPUS or something like thius with simple array Well, there's no discussion on this side so far. :) I wanted not to add a new header feature only for this but use existing method (sample event) so that it also can be recognized - at least to have very rough idea - by an incompatible version of the perf tool. Maybe the event has more information like total number of samples as a period. > > or if we are going to use event, maybe user event via > enum perf_user_event_type fits better IIRC some people don't want to add more user event types. Thanks, Namhyung -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/