Re: [PATCH v3 2/7] perf metric: Event "Compat" value supports matching multiple identifiers

[John Garry]

On 30/05/2023 10:19, Jing Zhang wrote:
> The jevent "Compat" is used for uncore PMU alias or metric definitions.
>
> The same PMU driver has different PMU identifiers due to different hardware
> versions and types, but they may have some common PMU event/metric. Since a
> Compat value can only match one identifier, when adding the same event
> alias and metric to PMUs with different identifiers, each identifier needs
> to be defined once, which is not streamlined enough.
>
> So let "Compat" value supports matching multiple identifiers. For example,
> the Compat value "arm_cmn600;arm_cmn700;arm_ci700" can match the PMU
> identifier "arm_cmn600X" or "arm_cmn700X" or "arm_ci700X", where "X" is a
> wildcard.

From checking the driver, it seems that we have model names 
"arm_cmn600" and "arm_cmn650". Are you saying that "arm_cmn600X" would 
match for those? I am most curious about how "arm_cmn600X" matches 
"arm_cmn650".

> Tokens in Unit field are delimited by ';'.

Thanks for taking a stab at solving this problem.

I have to admit that I am not the biggest fan of having multiple values 
to match in the "Compat" value possibly for every event. It doesn't 
really scale.

I would hope that there are at least some events which we are guaranteed 
to always be present. From what Robin said on the v2 series, for the 
implementations which we care about, events are generally added per 
subsequent version. So we should have some base set of fixed events.

If we are confident that we have a fixed set of base set of events, can 
we ensure that those events would not require this compat string which 
needs each version explicitly stated?

Robin, please let us know what you think of this.

Thanks,
John

> Signed-off-by: Jing Zhang <renyu.zj@xxxxxxxxxxxxxxxxx>
> ---
>   tools/perf/util/metricgroup.c | 24 +++++++++++++++++++++++-
>   1 file changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> index f3559be..c12ccd9 100644
> --- a/tools/perf/util/metricgroup.c
> +++ b/tools/perf/util/metricgroup.c
> @@ -456,6 +456,28 @@ struct metricgroup_iter_data {
>   	void *data;
>   };
>   
> +static bool match_pmu_identifier(const char *id, const char *compat)
> +{
> +	char *tmp = NULL, *tok, *str;
> +	bool res;
> +
> +	str = strdup(compat);
> +	if (!str)
> +		return false;
> +
> +	tok = strtok_r(str, ";", &tmp);
> +	for (; tok; tok = strtok_r(NULL, ";", &tmp)) {
> +		if (!strncmp(id, tok, strlen(tok))) {
> +			res = true;
> +			goto out;
> +		}
> +	}
> +	res = false;
> +out:
> +	free(str);
> +	return res;
> +}
> +
>   static int metricgroup__sys_event_iter(const struct pmu_metric *pm,
>   				       const struct pmu_metrics_table *table,
>   				       void *data)
> @@ -468,7 +490,7 @@ static int metricgroup__sys_event_iter(const struct pmu_metric *pm,
>   
>   	while ((pmu = perf_pmu__scan(pmu))) {
>   
> -		if (!pmu->id || strcmp(pmu->id, pm->compat))
> +		if (!pmu->id || !match_pmu_identifier(pmu->id, pm->compat))
>   			continue;
>   
>   		return d->fn(pm, table, d->data);