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

[Jing Zhang]

在 2023/1/6 下午11:59, John Garry 写道:
> 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@xxxxxxxxxxxxxxxxx>
>> Acked-by: Ian Rogers <irogers@xxxxxxxxxx>
> 
> 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.
> 

Thanks for pointing it out.

> 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.
> 

Ok, I will move the changes of sbsa.json and jevent.py to patch#2.

>> ---
>>   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).
> 

I'll factor out the pmu_core__find function in tools/perf/arch/arm64/util/pmu.c:

static const struct perf_pmu *pmu_core__find(void)
{
	struct perf_pmu *pmu = NULL;

	while ((pmu = perf_pmu__scan(pmu))) {
		if (!is_pmu_core(pmu->name))
			continue;

		/*
		 * The cpumap should cover all CPUs. Otherwise, some CPUs may
		 * not support some events or have different event IDs.
		 */
		if (pmu->cpus->nr != cpu__max_cpu().cpu)
			return NULL;
		return pmu;
	}

	return NULL;
}

>> +    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?
> 

Will do.

>> +}
>> 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.
> 

Does cpu_cycles_per_slot mean "cpu cycles per slot"? In the documemt, Slots mean operation width.
If slots are 5, the largest value by which the STALL_SLOT PMU event may increment in one cycle is 5.
So, maybe perf_pmu__cpu_slots_per_cycle() could be more accurate？