Re: [PATCH v1 1/2] perf expr: Make the evaluation of & and | logical and lazy

[Jiri Olsa <olsajiri@gmail.com>]

On Thu, May 04, 2023 at 12:58:02PM -0700, Ian Rogers wrote:
> Currently the & and | operators are only used in metric thresholds
> like (from the tma_retiring metric):
> tma_retiring > 0.7 | tma_heavy_operations > 0.1
> 
> Thresholds are always computed when present, but a lack events may
> mean the threshold can't be computed. This happens with the option
> --metric-no-threshold for say the metric tma_retiring on Tigerlake
> model CPUs. To fully compute the threshold tma_heavy_operations is
> needed and it needs the extra events of IDQ.MS_UOPS,
> UOPS_DECODED.DEC0, cpu/UOPS_DECODED.DEC0,cmask=1/ and
> IDQ.MITE_UOPS. So --metric-no-threshold is a useful option to reduce
> the number of events needed and potentially multiplexing of events.
> 
> Rather than just fail threshold computations like this, we may know a
> result from just the left or right-hand side. So, for tma_retiring if
> its value is "> 0.7" we know it is over the threshold. This allows the
> metric to have the threshold coloring, when possible, without all the
> counters being programmed.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>

lgtm

Acked-by: Jiri Olsa <jolsa@kernel.org>

jirka

> ---
>  tools/perf/tests/expr.c | 40 +++++++++++++++++++
>  tools/perf/util/expr.y  | 86 +++++++++++++++++++++++++++++++++--------
>  2 files changed, 109 insertions(+), 17 deletions(-)
> 
> diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
> index cbf0e0c74906..45c7fedb797a 100644
> --- a/tools/perf/tests/expr.c
> +++ b/tools/perf/tests/expr.c
> @@ -184,6 +184,46 @@ static int test__expr(struct test_suite *t __maybe_unused, int subtest __maybe_u
>  			NULL, ctx) == 0);
>  	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 0);
>  
> +	/* The expression is a constant 0.0 without needing to evaluate EVENT1. */
> +	expr__ctx_clear(ctx);
> +	TEST_ASSERT_VAL("find ids",
> +			expr__find_ids("0 & EVENT1 > 0", NULL, ctx) == 0);
> +	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 0);
> +	expr__ctx_clear(ctx);
> +	TEST_ASSERT_VAL("find ids",
> +			expr__find_ids("EVENT1 > 0 & 0", NULL, ctx) == 0);
> +	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 0);
> +	expr__ctx_clear(ctx);
> +	TEST_ASSERT_VAL("find ids",
> +			expr__find_ids("1 & EVENT1 > 0", NULL, ctx) == 0);
> +	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 1);
> +	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "EVENT1", &val_ptr));
> +	expr__ctx_clear(ctx);
> +	TEST_ASSERT_VAL("find ids",
> +			expr__find_ids("EVENT1 > 0 & 1", NULL, ctx) == 0);
> +	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 1);
> +	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "EVENT1", &val_ptr));
> +
> +	/* The expression is a constant 1.0 without needing to evaluate EVENT1. */
> +	expr__ctx_clear(ctx);
> +	TEST_ASSERT_VAL("find ids",
> +			expr__find_ids("1 | EVENT1 > 0", NULL, ctx) == 0);
> +	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 0);
> +	expr__ctx_clear(ctx);
> +	TEST_ASSERT_VAL("find ids",
> +			expr__find_ids("EVENT1 > 0 | 1", NULL, ctx) == 0);
> +	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 0);
> +	expr__ctx_clear(ctx);
> +	TEST_ASSERT_VAL("find ids",
> +			expr__find_ids("0 | EVENT1 > 0", NULL, ctx) == 0);
> +	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 1);
> +	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "EVENT1", &val_ptr));
> +	expr__ctx_clear(ctx);
> +	TEST_ASSERT_VAL("find ids",
> +			expr__find_ids("EVENT1 > 0 | 0", NULL, ctx) == 0);
> +	TEST_ASSERT_VAL("find ids", hashmap__size(ctx->ids) == 1);
> +	TEST_ASSERT_VAL("find ids", hashmap__find(ctx->ids, "EVENT1", &val_ptr));
> +
>  	/* Test toplogy constants appear well ordered. */
>  	expr__ctx_clear(ctx);
>  	TEST_ASSERT_VAL("#num_cpus", expr__parse(&num_cpus, ctx, "#num_cpus") == 0);
> diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y
> index 250e444bf032..6b110f9f95c9 100644
> --- a/tools/perf/util/expr.y
> +++ b/tools/perf/util/expr.y
> @@ -123,20 +123,6 @@ static struct ids handle_id(struct expr_parse_ctx *ctx, char *id,
>   * constant value using OP. Its invariant that there are no ids.  If computing
>   * ids for non-constants union the set of IDs that must be computed.
>   */
> -#define BINARY_LONG_OP(RESULT, OP, LHS, RHS)				\
> -	if (!compute_ids || (is_const(LHS.val) && is_const(RHS.val))) { \
> -		assert(LHS.ids == NULL);				\
> -		assert(RHS.ids == NULL);				\
> -		if (isnan(LHS.val) || isnan(RHS.val)) {			\
> -			RESULT.val = NAN;				\
> -		} else {						\
> -			RESULT.val = (long)LHS.val OP (long)RHS.val;	\
> -		}							\
> -		RESULT.ids = NULL;					\
> -	} else {							\
> -	        RESULT = union_expr(LHS, RHS);				\
> -	}
> -
>  #define BINARY_OP(RESULT, OP, LHS, RHS)					\
>  	if (!compute_ids || (is_const(LHS.val) && is_const(RHS.val))) { \
>  		assert(LHS.ids == NULL);				\
> @@ -213,9 +199,75 @@ expr: NUMBER
>  }
>  | ID				{ $$ = handle_id(ctx, $1, compute_ids, /*source_count=*/false); }
>  | SOURCE_COUNT '(' ID ')'	{ $$ = handle_id(ctx, $3, compute_ids, /*source_count=*/true); }
> -| expr '|' expr { BINARY_LONG_OP($$, |, $1, $3); }
> -| expr '&' expr { BINARY_LONG_OP($$, &, $1, $3); }
> -| expr '^' expr { BINARY_LONG_OP($$, ^, $1, $3); }
> +| expr '|' expr
> +{
> +	if (is_const($1.val) && is_const($3.val)) {
> +		assert($1.ids == NULL);
> +		assert($3.ids == NULL);
> +		$$.ids = NULL;
> +		$$.val = (fpclassify($1.val) == FP_ZERO && fpclassify($3.val) == FP_ZERO) ? 0 : 1;
> +	} else if (is_const($1.val)) {
> +		assert($1.ids == NULL);
> +		if (fpclassify($1.val) == FP_ZERO) {
> +			$$ = $3;
> +		} else {
> +			$$.val = 1;
> +			$$.ids = NULL;
> +			ids__free($3.ids);
> +		}
> +	} else if (is_const($3.val)) {
> +		assert($3.ids == NULL);
> +		if (fpclassify($3.val) == FP_ZERO) {
> +			$$ = $1;
> +		} else {
> +			$$.val = 1;
> +			$$.ids = NULL;
> +			ids__free($1.ids);
> +		}
> +	} else {
> +		$$ = union_expr($1, $3);
> +	}
> +}
> +| expr '&' expr
> +{
> +	if (is_const($1.val) && is_const($3.val)) {
> +		assert($1.ids == NULL);
> +		assert($3.ids == NULL);
> +		$$.val = (fpclassify($1.val) != FP_ZERO && fpclassify($3.val) != FP_ZERO) ? 1 : 0;
> +		$$.ids = NULL;
> +	} else if (is_const($1.val)) {
> +		assert($1.ids == NULL);
> +		if (fpclassify($1.val) != FP_ZERO) {
> +			$$ = $3;
> +		} else {
> +			$$.val = 0;
> +			$$.ids = NULL;
> +			ids__free($3.ids);
> +		}
> +	} else if (is_const($3.val)) {
> +		assert($3.ids == NULL);
> +		if (fpclassify($3.val) != FP_ZERO) {
> +			$$ = $1;
> +		} else {
> +			$$.val = 0;
> +			$$.ids = NULL;
> +			ids__free($1.ids);
> +		}
> +	} else {
> +		$$ = union_expr($1, $3);
> +	}
> +}
> +| expr '^' expr
> +{
> +	if (is_const($1.val) && is_const($3.val)) {
> +		assert($1.ids == NULL);
> +		assert($3.ids == NULL);
> +		$$.val = (fpclassify($1.val) == FP_ZERO) != (fpclassify($3.val) == FP_ZERO) ? 1 : 0;
> +		$$.ids = NULL;
> +	} else {
> +		$$ = union_expr($1, $3);
> +	}
> +}
>  | expr '<' expr { BINARY_OP($$, <, $1, $3); }
>  | expr '>' expr { BINARY_OP($$, >, $1, $3); }
>  | expr '+' expr { BINARY_OP($$, +, $1, $3); }
> -- 
> 2.40.1.521.gf1e218fcd8-goog
>