Re: perf tools event parsing code

[Arnaldo Carvalho de Melo]

Em Sun, Aug 02, 2015 at 09:56:27PM +0200, Jiri Olsa escreveu:
> On Fri, Jul 31, 2015 at 05:55:32PM -0300, Arnaldo Carvalho de Melo wrote:
> > Trying to figure out why this cset, by Wangnan:

> > https://git.kernel.org/cgit/linux/kernel/git/acme/linux.git/commit/?h=perf/ebpf&id=42cb6deef348f6afece0ad6fd7b034bfb532000e

> > doesn't make the routine he associated with parsing '--event bpf_program.o',
> > ended up in this:
 
> that change looks ok to me, but this

Well, the function associated with parsing FOO.o with BPF is only called
when it is prefixed with './', i.e. needs some fix.

> backtrace is from pmu cpu lookup/parsing, please check below

Yeah, probably it is not called when we use ./bpf_program.o, will
check...

  (gdb) break pmu_str_check
  Breakpoint 1 at 0x4ad4ac: file util/parse-events.l, line 69.
  (gdb) run record -e ./bpf.o sleep 1
  Starting program: /root/bin/perf record -e ./bpf.o sleep 1
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib64/libthread_db.so.1".
  libbpf: failed to open ./bpf.o: No such file or directory
  bpf: failed to load ./bpf.o
  invalid or unsupported event: './bpf.o'
  Run 'perf list' for a list of valid events

   usage: perf record [<options>] [<command>]
      or: perf record [<options>] -- <command> [<options>]

      -e, --event <event>   event selector. use 'perf list' to list available events
  [Inferior 1 (process 4722) exited with code 0201]
  (gdb)

- Arnaldo

> > 
> > #0  parse_events__scan_bytes (yybytes=yybytes@entry=0x7fffffff8480 "event=0x2e,umask=0x4f\n", _yybytes_len=22, yyscanner=0x18e4c30)
> >     at util/parse-events-flex.c:3312
> > #1  0x00000000004addb3 in parse_events__scan_string (yystr=<optimized out>, yystr@entry=0x7fffffff8480 "event=0x2e,umask=0x4f\n", yyscanner=<optimized out>)
> >     at util/parse-events-flex.c:3274
> > #2  0x000000000048a5e7 in parse_events__scanner (str=str@entry=0x7fffffff8480 "event=0x2e,umask=0x4f\n", data=data@entry=0x7fffffff83f0, 
> >     start_token=start_token@entry=259) at util/parse-events.c:1081
> > #3  0x000000000048ca52 in parse_events_terms (terms=terms@entry=0x18e4a88, str=str@entry=0x7fffffff8480 "event=0x2e,umask=0x4f\n")
> >     at util/parse-events.c:1104
> > #4  0x00000000004b2497 in __perf_pmu__new_alias (list=list@entry=0x7fffffffa700, dir=dir@entry=0x7fffffff96b0 "/sys/bus/event_source/devices/cpu/events", 
> >     name=name@entry=0x18d864b "cache-references", desc=desc@entry=0x0, val=val@entry=0x7fffffff8480 "event=0x2e,umask=0x4f\n") at util/pmu.c:224
> > #5  0x00000000004b25c0 in perf_pmu__new_alias (list=list@entry=0x7fffffffa700, dir=dir@entry=0x7fffffff96b0 "/sys/bus/event_source/devices/cpu/events", 
> >     name=name@entry=0x18d864b "cache-references", file=file@entry=0x18d67e0) at util/pmu.c:258
> > #6  0x00000000004b2788 in pmu_aliases_parse (dir=dir@entry=0x7fffffff96b0 "/sys/bus/event_source/devices/cpu/events", head=head@entry=0x7fffffffa700)
> >     at util/pmu.c:313
> > #7  0x00000000004b2864 in pmu_aliases (name=name@entry=0x5b9c47 "cpu", head=head@entry=0x7fffffffa700) at util/pmu.c:340
> > #8  0x00000000004b328a in pmu_lookup (name=<optimized out>, name@entry=0x5b9c47 "cpu") at util/pmu.c:477
> > #9  0x00000000004b33de in perf_pmu__find (name=name@entry=0x5b9c47 "cpu") at util/pmu.c:541
> > #10 0x000000000048a445 in perf_pmu__parse_init () at util/parse-events.c:1008
> > #11 0x000000000048b86d in perf_pmu__parse_check (name=name@entry=0x18d6c40 "file.c") at util/parse-events.c:1054
> > #12 0x00000000004ad4e2 in pmu_str_check (scanner=scanner@entry=0x18d6f20) at util/parse-events.l:74
> 
> this is support for the event term shortcut, like using
> 
>   perf record -e mem-loads ...
>     
> instead of:
>     
>   perf record -e cpu/mem-loads/
> 
> it calls 'perf_pmu__find("cpu") which triggers 'cpu' pmu 
> lookup 'pmu_lookup("cpu")'
> 
> and that one triggers alias parsing above as well  ;-)
> 
> > #13 0x00000000004af78b in parse_events_lex (yylval_param=yylval_param@entry=0x7fffffffa900, yylloc_param=yylloc_param@entry=0x7fffffffa920, 
> >     yyscanner=yyscanner@entry=0x18d6f20) at util/parse-events.l:267
> > #14 0x00000000004b042c in parse_events_parse (_data=_data@entry=0x7fffffffbec0, scanner=0x18d6f20) at util/parse-events-bison.c:1570
> > #15 0x000000000048a5f6 in parse_events__scanner (str=str@entry=0x7fffffffe778 "file.c", data=data@entry=0x7fffffffbec0, start_token=start_token@entry=258)
> >     at util/parse-events.c:1086
> > #16 0x000000000048b955 in parse_events (evlist=0x18d7b90, str=str@entry=0x7fffffffe778 "file.c", err=err@entry=0x7fffffffbf10) at util/parse-events.c:1126
> 
> events parsing starts here ^^^
> 
> > #17 0x000000000048b9f7 in parse_events_option (opt=<optimized out>, str=0x7fffffffe778 "file.c", unset=<optimized out>) at util/parse-events.c:1224
> > #18 0x0000000000487f30 in get_value (p=p@entry=0x7fffffffc0b0, opt=0x831c00 <__record_options>, flags=flags@entry=1) at util/parse-options.c:151
> > #19 0x000000000048823e in parse_short_opt (p=p@entry=0x7fffffffc0b0, options=<optimized out>, options@entry=0x831c00 <__record_options>)
> >     at util/parse-options.c:230
> > #20 0x0000000000488d6e in parse_options_step (ctx=ctx@entry=0x7fffffffc0b0, options=options@entry=0x831c00 <__record_options>, 
> >     usagestr=usagestr@entry=0x599850 <__record_usage>) at util/parse-options.c:401
> > #21 0x000000000048918c in parse_options_subcommand (argc=argc@entry=5, argv=argv@entry=0x7fffffffe520, options=0x831c00 <__record_options>, 
> >     subcommands=subcommands@entry=0x0, usagestr=0x599850 <__record_usage>, flags=flags@entry=2) at util/parse-options.c:518
> > #22 0x00000000004892da in parse_options (argc=argc@entry=5, argv=argv@entry=0x7fffffffe520, options=<optimized out>, usagestr=<optimized out>, 
> >     flags=flags@entry=2) at util/parse-options.c:553
> > #23 0x000000000042ad70 in cmd_record (argc=5, argv=0x7fffffffe520, prefix=<optimized out>) at builtin-record.c:1102
> > #24 0x0000000000474253 in run_builtin (p=p@entry=0x83c7f0 <commands+144>, argc=argc@entry=5, argv=argv@entry=0x7fffffffe520) at perf.c:370
> > #25 0x000000000047443f in handle_internal_command (argc=5, argv=0x7fffffffe520) at perf.c:429
> > #26 0x00000000004744b0 in run_argv (argcp=argcp@entry=0x7fffffffe38c, argv=argv@entry=0x7fffffffe380) at perf.c:473
> > #27 0x0000000000474726 in main (argc=5, argv=0x7fffffffe520) at perf.c:588
> > (gdb) 
> > 
> > /me trying to figure out this problem, but also how to avoid doing all this
> > seemingly unnecessary work, i.e. reading everything on the sysfs pmu files when
> > trying to figure out if this is a bpf filter event (-e foo.o).
> 
> it's deep, but it's initialized only once.. after it's initialized,
> there's no other parsing
> 
> jirka
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