Re: [PATCH v6 1/7] perf vendor events arm64: Add common topdown L1 metrics

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

On 06/01/2023 15:05, Jing Zhang wrote:
> The metrics of topdown L1 are from ARM sbsa7.0 platform design doc[0],
> D37-38, which are standard. So put them in the common file sbsa.json of
> arm64, so that other cores besides n2/v2 can also be reused.
> 
> Slots may be different in each architecture, so added "#slots" literal
> to get different constant for each architecture.
> 
> The value of slots comes from the register PMMIR_EL1, which I can read
> in /sys/bus/event_source/device/armv8_pmuv3_*/caps/slots. PMMIR_EL1.SLOT
> might read as zero if the STALL_SLOT event is not implemented or the PMU
> version is lower than ID_AA64DFR0_EL1_PMUVer_V3P4.
> 
> [0] https://urldefense.com/v3/__https://documentation-service.arm.com/static/60250c7395978b529036da86?token=__;!!ACWV5N9M2RV99hQ!J5JW3y6GhaJUqLfbEAzWIy4GJOhUkHQN4D5hEv3Outpzd54fN1Nt4LNKGnuRtMAepS_Nit-KLSUW98tVfFR0TmMVGQ$
> 
> Signed-off-by: Jing Zhang <renyu.zj@linux.alibaba.com>
> Acked-by: Ian Rogers <irogers@google.com>

hmmm... you have made significant changes in this version (compared to 
previous), so I would not have picked up this tag. That's just my opinion.

As for the patchset org, I'd move the JSON change here into patch #2, 
and make this patch purely about add "slots" literal support for arm64.

> ---
>   tools/perf/arch/arm64/util/pmu.c           | 22 ++++++++++++++++++++++
>   tools/perf/pmu-events/arch/arm64/sbsa.json | 30 ++++++++++++++++++++++++++++++
>   tools/perf/pmu-events/jevents.py           |  2 ++
>   tools/perf/util/expr.c                     |  5 +++++
>   tools/perf/util/pmu.c                      |  5 +++++
>   tools/perf/util/pmu.h                      |  1 +
>   6 files changed, 65 insertions(+)
>   create mode 100644 tools/perf/pmu-events/arch/arm64/sbsa.json
> 
> diff --git a/tools/perf/arch/arm64/util/pmu.c b/tools/perf/arch/arm64/util/pmu.c
> index 477e513..227dadb 100644
> --- a/tools/perf/arch/arm64/util/pmu.c
> +++ b/tools/perf/arch/arm64/util/pmu.c
> @@ -3,6 +3,7 @@
>   #include <internal/cpumap.h>
>   #include "../../../util/cpumap.h"
>   #include "../../../util/pmu.h"
> +#include <api/fs/fs.h>
>   
>   const struct pmu_events_table *pmu_events_table__find(void)
>   {
> @@ -24,3 +25,24 @@ const struct pmu_events_table *pmu_events_table__find(void)
>   
>   	return NULL;
>   }
> +
> +int perf_pmu__get_slots(void)
> +{
> +	char path[PATH_MAX];
> +	unsigned long long slots = 0;
> +	struct perf_pmu *pmu = NULL;
> +
> +	while ((pmu = perf_pmu__scan(pmu)) != NULL) {
> +		if (is_pmu_core(pmu->name))
> +			break;
> +	}

There is a lot in common with arm64's pmu_events_table__find() - can you 
factor it out? I also prefer how we check for homogeneous CPUs in 
pmu_events_table__find() (which you should do, also).

> +	if (pmu) {
> +		scnprintf(path, PATH_MAX,
> +			EVENT_SOURCE_DEVICE_PATH "%s/caps/slots", pmu->name);
> +		/* The value of slots is not greater than INT_MAX, but sysfs__read_int
> +		 * can't read value with 0x prefix, so use sysfs__read_ull instead.
> +		 */
> +		sysfs__read_ull(path, &slots);
> +	}
> +	return (int)slots;
> +}
> diff --git a/tools/perf/pmu-events/arch/arm64/sbsa.json b/tools/perf/pmu-events/arch/arm64/sbsa.json
> new file mode 100644
> index 0000000..f678c37e
> --- /dev/null
> +++ b/tools/perf/pmu-events/arch/arm64/sbsa.json
> @@ -0,0 +1,30 @@
> +[
> +    {
> +        "MetricExpr": "stall_slot_frontend / (#slots * cpu_cycles)",
> +        "BriefDescription": "Frontend bound L1 topdown metric",
> +        "MetricGroup": "TopdownL1",
> +        "MetricName": "frontend_bound",
> +        "ScaleUnit": "100%"
> +    },
> +    {
> +        "MetricExpr": "(1 - op_retired / op_spec) * (1 - stall_slot / (#slots * cpu_cycles))",
> +        "BriefDescription": "Bad speculation L1 topdown metric",
> +        "MetricGroup": "TopdownL1",
> +        "MetricName": "bad_speculation",
> +        "ScaleUnit": "100%"
> +    },
> +    {
> +        "MetricExpr": "(op_retired / op_spec) * (1 - stall_slot / (#slots * cpu_cycles))",
> +        "BriefDescription": "Retiring L1 topdown metric",
> +        "MetricGroup": "TopdownL1",
> +        "MetricName": "retiring",
> +        "ScaleUnit": "100%"
> +    },
> +    {
> +        "MetricExpr": "stall_slot_backend / (#slots * cpu_cycles)",
> +        "BriefDescription": "Backend Bound L1 topdown metric",
> +        "MetricGroup": "TopdownL1",
> +        "MetricName": "backend_bound",
> +        "ScaleUnit": "100%"
> +    }
> +]
> diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/jevents.py
> index 4c398e0..0416b74 100755
> --- a/tools/perf/pmu-events/jevents.py
> +++ b/tools/perf/pmu-events/jevents.py
> @@ -358,6 +358,8 @@ def preprocess_arch_std_files(archpath: str) -> None:
>         for event in read_json_events(item.path, topic=''):
>           if event.name:
>             _arch_std_events[event.name.lower()] = event
> +        if event.metric_name:
> +          _arch_std_events[event.metric_name.lower()] = event
>   
>   
>   def print_events_table_prefix(tblname: str) -> None:
> diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
> index 00dcde3..3d67707 100644
> --- a/tools/perf/util/expr.c
> +++ b/tools/perf/util/expr.c
> @@ -19,6 +19,7 @@
>   #include <linux/zalloc.h>
>   #include <ctype.h>
>   #include <math.h>
> +#include "pmu.h"
>   
>   #ifdef PARSER_DEBUG
>   extern int expr_debug;
> @@ -448,6 +449,10 @@ double expr__get_literal(const char *literal, const struct expr_scanner_ctx *ctx
>   		result = topology->core_cpus_lists;
>   		goto out;
>   	}
> +	if (!strcmp("#slots", literal)) {
> +		result = perf_pmu__get_slots();
> +		goto out;
> +	}
>   
>   	pr_err("Unrecognized literal '%s'", literal);
>   out:
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index 2bdeb89..d4cace2 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -1993,3 +1993,8 @@ int perf_pmu__cpus_match(struct perf_pmu *pmu, struct perf_cpu_map *cpus,
>   	*ucpus_ptr = unmatched_cpus;
>   	return 0;
>   }
> +
> +int __weak perf_pmu__get_slots(void)
> +{
> +	return 0;

should this be NAN?

> +}
> diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
> index 69ca000..a2f7df8 100644
> --- a/tools/perf/util/pmu.h
> +++ b/tools/perf/util/pmu.h
> @@ -259,4 +259,5 @@ int perf_pmu__cpus_match(struct perf_pmu *pmu, struct perf_cpu_map *cpus,
>   
>   char *pmu_find_real_name(const char *name);
>   char *pmu_find_alias_name(const char *name);
> +int perf_pmu__get_slots(void);

I think that this name is a bit too vague. Maybe 
perf_pmu__cpu_cycles_per_slot() could be better.

>   #endif /* __PMU_H */

Thanks,
John