linux-kernel - Re: [PATCH 2/2] perf parse-events: Remove "not supported" hybrid cache events

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Date:   Thu, 22 Sep 2022 16:04:01 +0800
From:   Xing Zhengjun <zhengjun.xing@...ux.intel.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     acme@...nel.org, peterz@...radead.org, mingo@...hat.com,
        alexander.shishkin@...el.com, jolsa@...nel.org,
        namhyung@...nel.org, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...ux.intel.com
Subject: Re: [PATCH 2/2] perf parse-events: Remove "not supported" hybrid
 cache events



On 9/22/2022 11:16 AM, Ian Rogers wrote:
> On Wed, Sep 21, 2022 at 6:47 PM <zhengjun.xing@...ux.intel.com> wrote:
>>
>> From: Zhengjun Xing <zhengjun.xing@...ux.intel.com>
>>
>> By default, we create two hybrid cache events, one is for cpu_core, and
>> another is for cpu_atom. But Some hybrid hardware cache events are only
>> available on one CPU PMU. For example, the 'L1-dcache-load-misses' is only
>> available on cpu_core, while the 'L1-icache-loads' is only available on
>> cpu_atom. We need to remove "not supported" hybrid cache events. By
>> extending is_event_supported() to global API and using it to check if the
>> hybrid cache events are supported before being created, we can remove the
>> "not supported" hybrid cache events.
>>
>> Before:
>>
>>   # ./perf stat -e L1-dcache-load-misses,L1-icache-loads -a sleep 1
>>
>>   Performance counter stats for 'system wide':
>>
>>              52,570      cpu_core/L1-dcache-load-misses/
>>     <not supported>      cpu_atom/L1-dcache-load-misses/
>>     <not supported>      cpu_core/L1-icache-loads/
>>           1,471,817      cpu_atom/L1-icache-loads/
>>
>>         1.004915229 seconds time elapsed
>>
>> After:
>>
>>   # ./perf stat -e L1-dcache-load-misses,L1-icache-loads -a sleep 1
>>
>>   Performance counter stats for 'system wide':
>>
>>              54,510      cpu_core/L1-dcache-load-misses/
>>           1,441,286      cpu_atom/L1-icache-loads/
>>
>>         1.005114281 seconds time elapsed
>>
>> Fixes: 30def61f64ba ("perf parse-events: Create two hybrid cache events")
>> Signed-off-by: Zhengjun Xing <zhengjun.xing@...ux.intel.com>
>> Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>
>> ---
>>   tools/perf/util/parse-events-hybrid.c | 8 +++++++-
>>   tools/perf/util/print-events.c        | 2 +-
>>   tools/perf/util/print-events.h        | 3 ++-
>>   3 files changed, 10 insertions(+), 3 deletions(-)
>>
>> diff --git a/tools/perf/util/parse-events-hybrid.c b/tools/perf/util/parse-events-hybrid.c
>> index 284f8eabd3b9..cf2e1c2e968f 100644
>> --- a/tools/perf/util/parse-events-hybrid.c
>> +++ b/tools/perf/util/parse-events-hybrid.c
>> @@ -14,6 +14,7 @@
>>   #include "pmu.h"
>>   #include "pmu-hybrid.h"
>>   #include "perf.h"
>> +#include "print-events.h"
>>
>>   static void config_hybrid_attr(struct perf_event_attr *attr,
>>                                 int type, int pmu_type)
>> @@ -48,13 +49,18 @@ static int create_event_hybrid(__u32 config_type, int *idx,
>>          __u64 config = attr->config;
>>
>>          config_hybrid_attr(attr, config_type, pmu->type);
>> +
>> +       if (attr->type == PERF_TYPE_HW_CACHE
>> +           && !is_event_supported(attr->type, attr->config))
>> +               goto out;
> 
> A comment to explain this would be useful.

Thanks, I will add a comment in the next version.
> 
>> +
>>          evsel = parse_events__add_event_hybrid(list, idx, attr, name, metric_id,
>>                                                 pmu, config_terms);
>>          if (evsel)
>>                  evsel->pmu_name = strdup(pmu->name);
>>          else
>>                  return -ENOMEM;
> 
> For consistency should this use the "goto" pattern now? You can also
> handle the ENOMEM case for strdup.
> 
  Yes, I will add a strdup check in the next version.
>> -
>> +out:
>>          attr->type = type;
>>          attr->config = config;
>>          return 0;
>> diff --git a/tools/perf/util/print-events.c b/tools/perf/util/print-events.c
>> index 04050d4f6db8..fa5cc94cfcfe 100644
>> --- a/tools/perf/util/print-events.c
>> +++ b/tools/perf/util/print-events.c
>> @@ -239,7 +239,7 @@ void print_sdt_events(const char *subsys_glob, const char *event_glob,
>>          strlist__delete(sdtlist);
>>   }
>>
>> -static bool is_event_supported(u8 type, u64 config)
>> +bool is_event_supported(u8 type, u64 config)
> 
> This makes me tempted to say this function should be in parse-events.c.
> 
"is_event_supported" move to parse-events.c should be better, I will do 
it in the next version.

> Thanks,
> Ian
> 
>>   {
>>          bool ret = true;
>>          int open_return;
>> diff --git a/tools/perf/util/print-events.h b/tools/perf/util/print-events.h
>> index 1da9910d83a6..ad2902fd0507 100644
>> --- a/tools/perf/util/print-events.h
>> +++ b/tools/perf/util/print-events.h
>> @@ -1,14 +1,15 @@
>>   /* SPDX-License-Identifier: GPL-2.0 */
>>   #ifndef __PERF_PRINT_EVENTS_H
>>   #define __PERF_PRINT_EVENTS_H
>> -
>>   #include <stdbool.h>
>> +#include <linux/types.h>
>>
>>   struct event_symbol;
>>
>>   void print_events(const char *event_glob, bool name_only, bool quiet_flag,
>>                    bool long_desc, bool details_flag, bool deprecated,
>>                    const char *pmu_name);
>> +bool is_event_supported(u8 type, u64 config);
>>   int print_hwcache_events(const char *event_glob, bool name_only);
>>   void print_sdt_events(const char *subsys_glob, const char *event_glob,
>>                        bool name_only);
>> --
>> 2.25.1
>>

-- 
Zhengjun Xing