Re: [PATCH v1] perf pmu: Count sys and cpuid json events separately

[John Garry <john.g.garry@oracle.com>]

On 10/05/2024 18:36, Ian Rogers wrote:
> Sys events are eagerly loaded as each event has a compat option that
> may mean the event is or isn't associated with the PMU. These
> shouldn't be counted as loaded_json_events as that is used for json
> events matching the CPUID that may or may not have been loaded. The
> mismatch causes issues on ARM64 that uses sys events.
> 
> Reported-by: Jia He <justin.he@arm.com>
> Closes: https://urldefense.com/v3/__https://lore.kernel.org/lkml/20240510024729.1075732-1-justin.he@arm.com/__;!!ACWV5N9M2RV99hQ!KVhaRPLqS7T1s6p506Gv0zFNdlTR1exCUrXM3UIDr0EdrRFwrzM3W9ntkxw42jNeG01P7H78r0c-nz8FVQQ$
> Fixes: e6ff1eed3584 ("perf pmu: Lazily add JSON events")
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>   tools/perf/util/pmu.c | 70 ++++++++++++++++++++++++++++++-------------
>   tools/perf/util/pmu.h |  6 ++--
>   2 files changed, 53 insertions(+), 23 deletions(-)
> 
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index b3b072feef02..888ce9912275 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -36,6 +36,18 @@ struct perf_pmu perf_pmu__fake = {
>   
>   #define UNIT_MAX_LEN	31 /* max length for event unit name */
>   
> +enum event_source {
> +	/* An event loaded from /sys/devices/<pmu>/events. */
> +	EVENT_SRC_SYSFS,
> +	/* An event loaded from a CPUID matched json file. */
> +	EVENT_SRC_CPU_JSON,
> +	/*
> +	 * An event loaded from a /sys/devices/<pmu>/identifier matched json
> +	 * file.
> +	 */
> +	EVENT_SRC_SYS_JSON,

If a json sys event aliases to a EVENT_SRC_SYSFS event, this is 
considered a EVENT_SRC_SYS_JSON event source, right?

> +};
> +
>   /**
>    * struct perf_pmu_alias - An event either read from sysfs or builtin in
>    * pmu-events.c, created by parsing the pmu-events json files.
> @@ -521,7 +533,7 @@ static int update_alias(const struct pmu_event *pe,
>   
>   static int perf_pmu__new_alias(struct perf_pmu *pmu, const char *name,
>   				const char *desc, const char *val, FILE *val_fd,
> -				const struct pmu_event *pe)
> +			        const struct pmu_event *pe, enum event_source src)
>   {
>   	struct perf_pmu_alias *alias;
>   	int ret;
> @@ -574,25 +586,30 @@ static int perf_pmu__new_alias(struct perf_pmu *pmu, const char *name,
>   		}
>   		snprintf(alias->unit, sizeof(alias->unit), "%s", unit);
>   	}
> -	if (!pe) {
> -		/* Update an event from sysfs with json data. */
> -		struct update_alias_data data = {
> -			.pmu = pmu,
> -			.alias = alias,
> -		};
> -
> +	switch (src) {
> +	default:
> +	case EVENT_SRC_SYSFS:
>   		alias->from_sysfs = true;
>   		if (pmu->events_table) {
> +			/* Update an event from sysfs with json data. */
> +			struct update_alias_data data = {
> +				.pmu = pmu,
> +				.alias = alias,
> +			};
>   			if (pmu_events_table__find_event(pmu->events_table, pmu, name,
>   							 update_alias, &data) == 0)
> -				pmu->loaded_json_aliases++;
> +				pmu->cpu_json_aliases++;

seems strange that matching for EVENT_SRC_SYSFS increases 
pmu->cpu_json_aliases

>   		}
> -	}
> -
> -	if (!pe)
>   		pmu->sysfs_aliases++;
> -	else
> -		pmu->loaded_json_aliases++;
> +		break;
> +	case  EVENT_SRC_CPU_JSON:
> +		pmu->cpu_json_aliases++;
> +		break;
> +	case  EVENT_SRC_SYS_JSON:
> +		pmu->sys_json_aliases++;
> +		break;
> +
> +	}
>   	list_add_tail(&alias->list, &pmu->aliases);
>   	return 0;
>   }
> @@ -653,7 +670,8 @@ static int __pmu_aliases_parse(struct perf_pmu *pmu, int events_dir_fd)
>   		}
>   
>   		if (perf_pmu__new_alias(pmu, name, /*desc=*/ NULL,
> -					/*val=*/ NULL, file, /*pe=*/ NULL) < 0)
> +					/*val=*/ NULL, file, /*pe=*/ NULL,
> +					EVENT_SRC_SYSFS) < 0)
>   			pr_debug("Cannot set up %s\n", name);
>   		fclose(file);
>   	}
> @@ -946,7 +964,8 @@ static int pmu_add_cpu_aliases_map_callback(const struct pmu_event *pe,
>   {
>   	struct perf_pmu *pmu = vdata;
>   
> -	perf_pmu__new_alias(pmu, pe->name, pe->desc, pe->event, /*val_fd=*/ NULL, pe);
> +	perf_pmu__new_alias(pmu, pe->name, pe->desc, pe->event, /*val_fd=*/ NULL,
> +			    pe, EVENT_SRC_CPU_JSON);
>   	return 0;
>   }
>   
> @@ -981,13 +1000,14 @@ static int pmu_add_sys_aliases_iter_fn(const struct pmu_event *pe,
>   		return 0;
>   
>   	if (pmu_uncore_alias_match(pe->pmu, pmu->name) &&
> -			pmu_uncore_identifier_match(pe->compat, pmu->id)) {
> +	    pmu_uncore_identifier_match(pe->compat, pmu->id)) {
>   		perf_pmu__new_alias(pmu,
>   				pe->name,
>   				pe->desc,
>   				pe->event,
>   				/*val_fd=*/ NULL,
> -				pe);
> +				pe,
> +				EVENT_SRC_SYS_JSON);
>   	}
>   
>   	return 0;
> @@ -1082,6 +1102,12 @@ struct perf_pmu *perf_pmu__lookup(struct list_head *pmus, int dirfd, const char
>   	pmu->max_precise = pmu_max_precise(dirfd, pmu);
>   	pmu->alias_name = pmu_find_alias_name(pmu, dirfd);
>   	pmu->events_table = perf_pmu__find_events_table(pmu);
> +	/*
> +	 * Load the sys json events/aliases when loading the PMU as each event
> +	 * may have a different compat regular expression. We therefore can't
> +	 * know the number of sys json events/aliases without computing the
> +	 * regular expressions for them all.
> +	 */
>   	pmu_add_sys_aliases(pmu);
>   	list_add_tail(&pmu->list, pmus);
>   
> @@ -1739,12 +1765,14 @@ size_t perf_pmu__num_events(struct perf_pmu *pmu)
>   	size_t nr;
>   
>   	pmu_aliases_parse(pmu);
> -	nr = pmu->sysfs_aliases;
> +	nr = pmu->sysfs_aliases + pmu->sys_json_aliases;;
>   
>   	if (pmu->cpu_aliases_added)
> -		 nr += pmu->loaded_json_aliases;
> +		 nr += pmu->cpu_json_aliases;
>   	else if (pmu->events_table)
> -		nr += pmu_events_table__num_events(pmu->events_table, pmu) - pmu->loaded_json_aliases;
> +		nr += pmu_events_table__num_events(pmu->events_table, pmu) - pmu->cpu_json_aliases;
> +	else
> +		assert(pmu->cpu_json_aliases == 0);
>   
>   	return pmu->selectable ? nr + 1 : nr;
>   }
> diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
> index 561716aa2b25..b2d3fd291f02 100644
> --- a/tools/perf/util/pmu.h
> +++ b/tools/perf/util/pmu.h
> @@ -123,8 +123,10 @@ struct perf_pmu {
>   	const struct pmu_events_table *events_table;
>   	/** @sysfs_aliases: Number of sysfs aliases loaded. */
>   	uint32_t sysfs_aliases;
> -	/** @sysfs_aliases: Number of json event aliases loaded. */
> -	uint32_t loaded_json_aliases;
> +	/** @cpu_json_aliases: Number of json event aliases loaded specific to the CPUID. */
> +	uint32_t cpu_json_aliases;

it seems strange that we allow a pmu to have both cpu_json_aliases and 
sys_json_aliases count. A union could be used, but that would complicate 
things.

> +	/** @sys_json_aliases: Number of json event aliases loaded matching the PMU's identifier. */
> +	uint32_t sys_json_aliases;
>   	/** @sysfs_aliases_loaded: Are sysfs aliases loaded from disk? */
>   	bool sysfs_aliases_loaded;
>   	/**