Re: [PATCH v2 1/2] perf expr: Add d_ratio operation

[Jiri Olsa <jolsa@redhat.com>]

On Wed, Jun 10, 2020 at 04:58:22PM -0700, Ian Rogers wrote:
> d_ratio avoids division by 0 yielding infinity, such as when a counter
> doesn't get scheduled. An example usage is:
> 
> {
>     "BriefDescription": "DCache L1 misses",
>     "MetricExpr": "d_ratio(MEM_LOAD_RETIRED.L1_MISS, MEM_LOAD_RETIRED.L1_HIT + MEM_LOAD_RETIRED.L1_MISS + MEM_LOAD_RETIRED.FB_HIT)",
>     "MetricGroup": "DCache;DCache_L1",
>     "MetricName": "DCache_L1_Miss",
>     "ScaleUnit": "100%",
> }
> 
> Signed-off-by: Ian Rogers <irogers@google.com>

Acked-by: Jiri Olsa <jolsa@redhat.com>

thanks,
jirka

> ---
>  tools/perf/tests/expr.c |  2 ++
>  tools/perf/util/expr.l  |  1 +
>  tools/perf/util/expr.y  | 14 ++++++++++++--
>  3 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
> index 1cb02ca2b15f..c4877b36ab58 100644
> --- a/tools/perf/tests/expr.c
> +++ b/tools/perf/tests/expr.c
> @@ -39,6 +39,8 @@ int test__expr(struct test *t __maybe_unused, int subtest __maybe_unused)
>  	ret |= test(&ctx, "1+1 if 3*4 else 0", 2);
>  	ret |= test(&ctx, "1.1 + 2.1", 3.2);
>  	ret |= test(&ctx, ".1 + 2.", 2.1);
> +	ret |= test(&ctx, "d_ratio(1, 2)", 0.5);
> +	ret |= test(&ctx, "d_ratio(2.5, 0)", 0);
>  
>  	if (ret)
>  		return ret;
> diff --git a/tools/perf/util/expr.l b/tools/perf/util/expr.l
> index f397bf8b1a48..298d86660a96 100644
> --- a/tools/perf/util/expr.l
> +++ b/tools/perf/util/expr.l
> @@ -100,6 +100,7 @@ symbol		({spec}|{sym})+
>  		}
>  	}
>  
> +d_ratio		{ return D_RATIO; }
>  max		{ return MAX; }
>  min		{ return MIN; }
>  if		{ return IF; }
> diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y
> index bf3e898e3055..fe145344bb39 100644
> --- a/tools/perf/util/expr.y
> +++ b/tools/perf/util/expr.y
> @@ -10,6 +10,14 @@
>  #include "smt.h"
>  #include <string.h>
>  
> +static double d_ratio(double val0, double val1)
> +{
> +	if (val1 == 0) {
> +		return 0;
> +	}
> +	return  val0 / val1;
> +}
> +
>  %}
>  
>  %define api.pure full
> @@ -28,7 +36,7 @@
>  %token <num> NUMBER
>  %token <str> ID
>  %destructor { free ($$); } <str>
> -%token MIN MAX IF ELSE SMT_ON
> +%token MIN MAX IF ELSE SMT_ON D_RATIO
>  %left MIN MAX IF
>  %left '|'
>  %left '^'
> @@ -64,7 +72,8 @@ other: ID
>  }
>  |
>  MIN | MAX | IF | ELSE | SMT_ON | NUMBER | '|' | '^' | '&' | '-' | '+' | '*' | '/' | '%' | '(' | ')' | ','
> -
> +|
> +D_RATIO
>  
>  all_expr: if_expr			{ *final_val = $1; }
>  	;
> @@ -105,6 +114,7 @@ expr:	  NUMBER
>  	| MIN '(' expr ',' expr ')' { $$ = $3 < $5 ? $3 : $5; }
>  	| MAX '(' expr ',' expr ')' { $$ = $3 > $5 ? $3 : $5; }
>  	| SMT_ON		 { $$ = smt_on() > 0; }
> +	| D_RATIO '(' expr ',' expr ')' { $$ = d_ratio($3,$5); }
>  	;
>  
>  %%
> -- 
> 2.27.0.278.ge193c7cf3a9-goog
>