Re: [PATCH] perf evlist: Fix the warning logic about warn_user_request_cpu

[James Clark <james.clark@linaro.org>]

On 09/12/2024 2:42 pm, Arnaldo Carvalho de Melo wrote:
> On Mon, Mar 18, 2024 at 08:11:50PM +0800, Chunxin Zang wrote:
>> The old logic in evlist__warn_user_requested_cpus incorrectly output
>> the warning message when I run 'perf record -C xxx' command on my
>> context(the cpu has 8 performance-cores and 8 efficient-cores.).
>>
>> The old warning like this:
>>    # perf record -C 17
>>    WARNING: A requested CPU in '17' is not supported by PMU 'cpu_core' (CPUs 0-15) for event 'cycles:P'
>>    # perf record -C 14
>>    WARNING: A requested CPU in '14' is not supported by PMU 'cpu_atom' (CPUs 16-23) for event 'cycles:P'
>>    # perf record -C 14-17
>>    WARNING: A requested CPU in '15-16' is not supported by PMU 'cpu_atom' (CPUs 16-23) for event 'cycles:P'
>>    WARNING: A requested CPU in '15-16' is not supported by PMU 'cpu_core' (CPUs 0-15) for event 'cycles:P'
>>
>> After patching, the warning is as follows
>>    # perf record -C 17
>>    WARNING: A requested CPU '17' in '17' is not supported by PMU 'cpu_atom' (CPUs 16-23) for event 'cycles:P'
> 
> Looks wrong, i.e. I ask for CPU 17 and it says it is not in the range
> 16-23?
> 
> Ditto for the rest, no?
> 
> - Arnaldo
> 

Is this fix needed if we have 
https://lore.kernel.org/linux-perf-users/20241114160450.295844-1-james.clark@linaro.org/T/#t 
?

I think some of these warnings might not be shown in that case due to 
fixing the other issue.

>>    # perf record -C 14
>>    WARNING: A requested CPU '14' in '14' is not supported by PMU 'cpu_core' (CPUs 0-15) for event 'cycles:P'
>>    # perf record -C 15-18
>>    WARNING: A requested CPU '16-18' in '15-18' is not supported by PMU 'cpu_atom' (CPUs 16-23) for event 'cycles:P'
>>    WARNING: A requested CPU '15' in '15-18' is not supported by PMU 'cpu_core' (CPUs 0-15) for event 'cycles:P'
>>
>> Signed-off-by: Chunxin Zang <spring.cxz@gmail.com>
>> Reviewed-by: Chen Yang <yangchen11@lixiang.com>
>> ---
>>   tools/perf/util/evlist.c | 14 +++++++++-----
>>   1 file changed, 9 insertions(+), 5 deletions(-)
>>
>> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
>> index 55a300a0977b..82fee2e29966 100644
>> --- a/tools/perf/util/evlist.c
>> +++ b/tools/perf/util/evlist.c
>> @@ -2514,12 +2514,16 @@ void evlist__warn_user_requested_cpus(struct evlist *evlist, const char *cpu_lis
>>   
>>   		to_test = pmu && pmu->is_core ? pmu->cpus : cpu_map__online();
>>   		intersect = perf_cpu_map__intersect(to_test, user_requested_cpus);
>> -		if (!perf_cpu_map__equal(intersect, user_requested_cpus)) {
>> -			char buf[128];
>>   
>> -			cpu_map__snprint(to_test, buf, sizeof(buf));
>> -			pr_warning("WARNING: A requested CPU in '%s' is not supported by PMU '%s' (CPUs %s) for event '%s'\n",
>> -				cpu_list, pmu ? pmu->name : "cpu", buf, evsel__name(pos));
>> +		if (intersect && perf_cpu_map__is_subset(user_requested_cpus, intersect)) {
>> +			char buf_test[128];
>> +			char buf_intersect[128];
>> +
>> +			cpu_map__snprint(to_test, buf_test, sizeof(buf_test));
>> +			cpu_map__snprint(intersect, buf_intersect, sizeof(buf_intersect));
>> +			pr_warning("WARNING: A requested CPU '%s' in '%s' is not supported by "
>> +				   "PMU '%s' (CPUs %s) for event '%s'\n", buf_intersect, cpu_list,
>> +				   pmu ? pmu->name : "cpu", buf_test, evsel__name(pos));
>>   		}
>>   		perf_cpu_map__put(intersect);
>>   	}
>> -- 
>> 2.34.1
>