Re: [PATCH V2 3/6] perf tools: add infrastructure for PMU specific configuration

[Mathieu Poirier]

On 26 July 2016 at 14:41, Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
> On Fri, Jul 22, 2016 at 12:24:48PM -0600, Mathieu Poirier wrote:
>
> SNIP
>
>> > diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
>> > --- a/tools/perf/util/parse-events.y
>> > +++ b/tools/perf/util/parse-events.y
>> > @@ -602,12 +602,12 @@ PE_NAME array '=' PE_VALUE
>> >         $$ = term;
>> >  }
>> >  |
>> > -PE_DRV_CFG_TERM
>> > +'@' PE_DRV_CFG_TERM
>> >  {
>> >         struct parse_events_term *term;
>> >
>> >         ABORT_ON(parse_events_term__str(&term, PARSE_EVENTS__TERM_TYPE_DRV_CFG,
>> > -                                       $1, $1, &@1, NULL));
>> > +                                       $2, $2, &@2, NULL));
>> >         $$ = term;
>> >  }
>> >
>>
>> I've been experimenting with the above solution and it is not yielding
>> the results one might think at first glance.
>>
>> If we use the example: -e event/@cfg1/ ...
>>
>> First if we leave things exactly the way they are suggested in the
>> code snippet flex doesn't know what do to with the '@' character and
>> returns an error.  To deal with that a new clause
>>
>> "@"        { return '@'; }
>>
>> can be inserted in the config state.  But that doesn't link '@' with
>> 'cfg1', and 'cfg1' gets interpreted as a PE_NAME.  Introducing a new
>> state upon hitting '@' would get us around that but we are moving away
>> from our initial goal of keeping things simple.
>
> hum, then how about keeping the flex atoms simple like for the
> other terms and do something like below.. untested ;-)
>
> thanks,
> jirka
>
>
> ---
> diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
> index 1f7e11a6c5b3..8ba228e1c150 100644
> --- a/tools/perf/util/parse-events.l
> +++ b/tools/perf/util/parse-events.l
> @@ -53,16 +53,6 @@ static int str(yyscan_t scanner, int token)
>         return token;
>  }
>
> -static int drv_str(yyscan_t scanner, int token)
> -{
> -       YYSTYPE *yylval = parse_events_get_lval(scanner);
> -       char *text = parse_events_get_text(scanner);
> -
> -       /* Strip off the '@' */
> -       yylval->str = strdup(text + 1);
> -       return token;
> -}
> -
>  #define REWIND(__alloc)                                \
>  do {                                                           \
>         YYSTYPE *__yylval = parse_events_get_lval(yyscanner);   \
> @@ -134,7 +124,6 @@ num_hex             0x[a-fA-F0-9]+
>  num_raw_hex    [a-fA-F0-9]+
>  name           [a-zA-Z_*?][a-zA-Z0-9_*?.]*
>  name_minus     [a-zA-Z_*?][a-zA-Z0-9\-_*?.:]*
> -drv_cfg_term   [a-zA-Z0-9_\.]+(=[a-zA-Z0-9_*?\.:]+)?
>  /* If you add a modifier you need to update check_modifier() */
>  modifier_event [ukhpPGHSDI]+
>  modifier_bp    [rwx]{1,3}
> @@ -216,11 +205,11 @@ no-inherit                { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_NOINHERIT); }
>  overwrite              { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_OVERWRITE); }
>  no-overwrite           { return term(yyscanner, PARSE_EVENTS__TERM_TYPE_NOOVERWRITE); }
>  ,                      { return ','; }
> +"@"                    { return '@'; }
>  "/"                    { BEGIN(INITIAL); return '/'; }
>  {name_minus}           { return str(yyscanner, PE_NAME); }
>  \[all\]                        { return PE_ARRAY_ALL; }
>  "["                    { BEGIN(array); return '['; }
> -@{drv_cfg_term}                { return drv_str(yyscanner, PE_DRV_CFG_TERM); }
>  }
>
>  <mem>{
> diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
> index 879115f93edc..7e03e93dabca 100644
> --- a/tools/perf/util/parse-events.y
> +++ b/tools/perf/util/parse-events.y
> @@ -602,12 +602,12 @@ PE_NAME array '=' PE_VALUE
>         $$ = term;
>  }
>  |
> -PE_DRV_CFG_TERM
> +'@' PE_NAME '=' PE_NAME
>  {
>         struct parse_events_term *term;
>
>         ABORT_ON(parse_events_term__str(&term, PARSE_EVENTS__TERM_TYPE_DRV_CFG,
> -                                       $1, $1, &@1, NULL));
> +                                       $2, $4, &@2, &@4));
>         $$ = term;
>  }
>

The problem here is that the correlation between the first and the
second PE_NAME is lost and instead of seeing "PE_NAME=PE_NAME", the
kernel only gets the value associated with the second PE_NAME.

For example,

-e event/@cfg1=value1,@cfg2=value2/ ...

The above code will send "value1" and "value2" to the kernel driver
where there is no way to know what configurable the values correspond
to.  To go around that we'd have to concatenate $2 and $4 in function
parse_events_term__str() (or new_term()) when @type_term ==
PARSE_EVENTS__TERM_TYPE_DRV_CFG, something that definitely looks
hackish to me.

Thanks,
Mathieu