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SubjectRe: [PATCH v3 3/3] perf tools: Enable on a list of CPUs for hybrid
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Hi Jiri,

On 7/22/2021 6:19 PM, Jiri Olsa wrote:
> On Wed, Jul 21, 2021 at 12:30:11PM +0800, Jin, Yao wrote:
>> Hi Jiri,
>>
>> On 7/20/2021 5:16 PM, Jiri Olsa wrote:
>>> On Tue, Jul 20, 2021 at 03:07:02PM +0800, Jin, Yao wrote:
>>>
>>> SNIP
>>>
>>>>
>>>> OK, evlist__fix_cpus() is better, use this name in v4.
>>>>
>>>>>> +{
>>>>>> + struct perf_cpu_map *cpus;
>>>>>> + struct evsel *evsel, *tmp;
>>>>>> + struct perf_pmu *pmu;
>>>>>> + int ret, unmatched_count = 0, events_nr = 0;
>>>>>> +
>>>>>> + if (!perf_pmu__has_hybrid() || !cpu_list)
>>>>>> + return 0;
>>>>>> +
>>>>>> + cpus = perf_cpu_map__new(cpu_list);
>>>>>> + if (!cpus)
>>>>>> + return -1;
>>>>>> +
>>>>>> + evlist__for_each_entry_safe(evlist, tmp, evsel) {
>>>>>> + struct perf_cpu_map *matched_cpus, *unmatched_cpus;
>>>>>> + char buf1[128], buf2[128];
>>>>>> +
>>>>>> + pmu = perf_pmu__find_hybrid_pmu(evsel->pmu_name);
>>>>>> + if (!pmu)
>>>>>> + continue;
>>>>>> +
>>>>>> + ret = perf_pmu__cpus_match(pmu, cpus, &matched_cpus,
>>>>>> + &unmatched_cpus);
>>>>>> + if (ret)
>>>>>> + goto out;
>>>>>> +
>>>>>> + events_nr++;
>>>>>> +
>>>>>> + if (matched_cpus->nr > 0 && (unmatched_cpus->nr > 0 ||
>>>>>> + matched_cpus->nr < cpus->nr ||
>>>>>> + matched_cpus->nr < pmu->cpus->nr)) {
>>>>>> + perf_cpu_map__put(evsel->core.cpus);
>>>>>> + perf_cpu_map__put(evsel->core.own_cpus);
>>>>>> + evsel->core.cpus = perf_cpu_map__get(matched_cpus);
>>>>>> + evsel->core.own_cpus = perf_cpu_map__get(matched_cpus);
>>>>>
>>>>> I'm bit confused in here.. AFAIUI there's 2 evsel objects create
>>>>> for hybrid 'cycles' ... should they have already proper cpus set?
>>>>>
>>>>
>>>> For 'cycles', yes two evsels are created automatically. One is for atom CPU
>>>> (e.g. 8-11), the other is for core CPU (e.g. 0-7). In this example, these 2
>>>> evsels have already the cpus set.
>>>
>>> hum, so those evsels are created with pmu's cpus, right?
>>>
>>
>> Yes, that's right. But we also check and adjust the evsel->cpus by using
>> user's cpu list on hybrid (what the evlist__use_cpu_list() does).
>>
>>>>
>>>> While the 'cpus' here is just the user specified cpu list.
>>>> cpus = perf_cpu_map__new(cpu_list);
>>>
>>> then I think they will be changed by evlist__create_maps
>>> with whatever user wants?
>>>
>>
>> No, it will not be changed by evlist__create_maps.
>>
>> In evlist__create_maps(),
>> evlist->core.has_user_cpus = !!target->cpu_list && !target->hybrid;
>>
>> It disables has_user_cpus for hybrid.
>>
>> So in __perf_evlist__propagate_maps, they will not be changed by evlist->cpus.
>>
>> if (!evsel->own_cpus || evlist->has_user_cpus) {
>> perf_cpu_map__put(evsel->cpus);
>> evsel->cpus = perf_cpu_map__get(evlist->cpus);
>>
>>> could we just change __perf_evlist__propagate_maps to follow
>>> pmu's cpus?
>>>
>>
>> In __perf_evlist__propagate_maps, it has already followed pmu's cpus because
>> the evlist->has_user_cpus is false for hybrid.
>
> sorry for delay
>

Never mind. :)

> ok, so we first fix the cpus on hybrid events and then
> propagate maps.. I guess it's ok, because it's in libperf
> and that has no notion of hybrid so far
>

Yes. If we want the libperf to be hybrid aware, the interface has to be modified but actually we
need to avoid modifying the libperf interface. So I finally decide to adjust the evsel->cpus first
and then propatate maps.

> could you please rename that function so it's also obvious
> it's for hybrid only
>
> evlist__fix_hybrid_cpus ? not sure ;-)
>

Sure, I will rename the funciton in v4.

> and add some comment with example to explain what the
> function is doing
>

Got it!

Thanks
Jin Yao

> thanks,
> jirka
>

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