Messages in this thread | | | Date | Fri, 13 May 2022 13:32:42 -0400 | Subject | Re: [PATCH V2 22/23] perf tools: Allow system-wide events to keep their own CPUs | From | "Liang, Kan" <> |
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On 5/13/2022 12:42 PM, Namhyung Kim wrote: > On Fri, May 13, 2022 at 9:11 AM Adrian Hunter <adrian.hunter@intel.com> wrote: >> >> On 13/05/22 18:46, Liang, Kan wrote: >>> >>> >>> On 5/13/2022 11:21 AM, Adrian Hunter wrote: >>>> On 13/05/22 17:12, Liang, Kan wrote: >>>>> >>>>> >>>>> On 5/13/2022 12:48 AM, Adrian Hunter wrote: >>>>>> On 12/05/22 21:53, Namhyung Kim wrote: >>>>>>> On Thu, May 12, 2022 at 3:35 AM Adrian Hunter <adrian.hunter@intel.com> wrote: >>>>>>>> >>>>>>>> On 12/05/22 08:27, Namhyung Kim wrote: >>>>>>>>> On Fri, May 6, 2022 at 5:27 AM Adrian Hunter <adrian.hunter@intel.com> wrote: >>>>>>>>>> >>>>>>>>>> Currently, user_requested_cpus supplants system-wide CPUs when the evlist >>>>>>>>>> has_user_cpus. Change that so that system-wide events retain their own >>>>>>>>>> CPUs and they are added to all_cpus. >>>>>>>>>> >>>>>>>>>> Acked-by: Ian Rogers <irogers@google.com> >>>>>>>>>> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> >>>>>>>>>> --- >>>>>>>>>> tools/lib/perf/evlist.c | 11 +++++------ >>>>>>>>>> 1 file changed, 5 insertions(+), 6 deletions(-) >>>>>>>>>> >>>>>>>>>> diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c >>>>>>>>>> index 1c801f8da44f..9a6801b53274 100644 >>>>>>>>>> --- a/tools/lib/perf/evlist.c >>>>>>>>>> +++ b/tools/lib/perf/evlist.c >>>>>>>>>> @@ -40,12 +40,11 @@ static void __perf_evlist__propagate_maps(struct perf_evlist *evlist, >>>>>>>>>> * We already have cpus for evsel (via PMU sysfs) so >>>>>>>>>> * keep it, if there's no target cpu list defined. >>>>>>>>>> */ >>>>>>>>>> - if (!evsel->own_cpus || evlist->has_user_cpus) { >>>>>>>>>> - perf_cpu_map__put(evsel->cpus); >>>>>>>>>> - evsel->cpus = perf_cpu_map__get(evlist->user_requested_cpus); >>>>>>>>>> - } else if (!evsel->system_wide && >>>>>>>>>> - !evsel->requires_cpu && >>>>>>>>>> - perf_cpu_map__empty(evlist->user_requested_cpus)) { >>>>>>>>>> + if (!evsel->own_cpus || >>>>>>>>>> + (!evsel->system_wide && evlist->has_user_cpus) || >>>>>>>>>> + (!evsel->system_wide && >>>>>>>>>> + !evsel->requires_cpu && >>>>>>>>>> + perf_cpu_map__empty(evlist->user_requested_cpus))) { >>>>>>>>> >>>>>>>>> This is getting hard to understand. IIUC this propagation basically >>>>>>>>> sets user requested cpus to evsel unless it has its own cpus, right? >>>>>>>> >>>>>>>> I put the conditional logic altogether because that is kernel style but >>>>>>>> it does make it practically unreadable. >>>>>>>> >>>>>>>> If we start with the original logic: >>>>>>>> >>>>>>>> if (!evsel->own_cpus || evlist->has_user_cpus) { >>>>>>>> perf_cpu_map__put(evsel->cpus); >>>>>>>> evsel->cpus = perf_cpu_map__get(evlist->user_requested_cpus); >>>>>>>> } else if (!evsel->system_wide && perf_cpu_map__empty(evlist->user_requested_cpus)) { >>>>>>>> perf_cpu_map__put(evsel->cpus); >>>>>>>> evsel->cpus = perf_cpu_map__get(evlist->user_requested_cpus); >>>>>>>> } else if (evsel->cpus != evsel->own_cpus) { >>>>>>>> perf_cpu_map__put(evsel->cpus); >>>>>>>> evsel->cpus = perf_cpu_map__get(evsel->own_cpus); >>>>>>>> } >>>>>>>> >>>>>>>> Then make it more readable, i.e. same functionality >>>>>>>> >>>>>>>> struct perf_cpu_map *cpus; >>>>>>>> >>>>>>>> if (!evsel->own_cpus || evlist->has_user_cpus) >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> else if (!evsel->system_wide && perf_cpu_map__empty(evlist->user_requested_cpus)) >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> else >>>>>>>> cpus = evsel->own_cpus; >>>>>>>> >>>>>>>> if (evsel->cpus != cpus) { >>>>>>>> perf_cpu_map__put(evsel->cpus); >>>>>>>> evsel->cpus = perf_cpu_map__get(cpus); >>>>>>>> } >>>>>>>> >>>>>>>> Then separate out the conditions, i.e. still same functionality >>>>>>>> >>>>>>>> if (!evsel->own_cpus) >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> else if (evlist->has_user_cpus) >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> else if (evsel->system_wide) >>>>>>>> cpus = evsel->own_cpus; >>>>>>>> else if (perf_cpu_map__empty(evlist->user_requested_cpus)) /* per-thread */ >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> else >>>>>>>> cpus = evsel->own_cpus; >>>>>>>> >>>>>>>> Then add the new requires_cpu flag: >>>>>>>> >>>>>>>> if (!evsel->own_cpus) >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> else if (evlist->has_user_cpus) >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> else if (evsel->system_wide) >>>>>>>> cpus = evsel->own_cpus; >>>>>>>> - else if (perf_cpu_map__empty(evlist->user_requested_cpus)) /* per-thread */ >>>>>>>> + else if (!evsel->requres_cpu && perf_cpu_map__empty(evlist->user_requested_cpus)) /* per-thread */ >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> else >>>>>>>> cpus = evsel->own_cpus; >>>>>>>> >>>>>>>> Then make system_wide keep own_cpus even if has_user_cpus: >>>>>>>> >>>>>>>> if (!evsel->own_cpus) >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> + else if (evsel->system_wide) >>>>>>>> + cpus = evsel->own_cpus; >>>>>>>> else if (evlist->has_user_cpus) >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> - else if (evsel->system_wide) >>>>>>>> - cpus = evsel->own_cpus; >>>>>>>> else if (!evsel->requres_cpu && perf_cpu_map__empty(evlist->user_requested_cpus)) /* per-thread */ >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> else >>>>>>>> cpus = evsel->own_cpus; >>>>>>>> >>>>>>>> Which leaves: >>>>>>>> >>>>>>>> if (!evsel->own_cpus) >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> else if (evsel->system_wide) >>>>>>>> cpus = evsel->own_cpus; >>>>>>>> else if (evlist->has_user_cpus) >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> else if (!evsel->requres_cpu && perf_cpu_map__empty(evlist->user_requested_cpus)) /* per-thread */ >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> else >>>>>>>> cpus = evsel->own_cpus; >>>>>>>> >>>>>>>> And putting it back together: >>>>>>>> >>>>>>>> if (!evsel->own_cpus || >>>>>>>> (!evsel->system_wide && evlist->has_user_cpus) || >>>>>>>> (!evsel->system_wide && >>>>>>>> !evsel->requires_cpu && >>>>>>>> perf_cpu_map__empty(evlist->user_requested_cpus))) { >>>>>>>> cpus = evlist->user_requested_cpus; >>>>>>>> else >>>>>>>> cpus = evsel->own_cpus; >>>>>>>> >>>>>>>> Perhaps I shouldn't put it together? >>>>>>> >>>>>>> Cool, thanks a lot for explaining it in detail. >>>>>>> I do not oppose your change but little worried about the >>>>>>> complexity. And I think we have some issues with uncore >>>>>>> events already. >>>>>> >>>>>> Yes it is a bit complicated because we are handling >>>>>> many different use cases. >>>>>> >>>>>>> >>>>>>> So do you have any idea where evsel->own_cpus >>>>>>> doesn't propagate to evsel->cpus? >>>>>> >>>>>> We let the user's list of CPUs override it i.e. the >>>>>> evlist->has_user_cpus case. Essentially we are expecting >>>>>> the user to know what they are doing. >>>>>> >>>>>>> >>>>>>> I think evsel->system_wide and evsel->requires_cpu >>>>>>> can be replaced to check evsel->own_cpus instead. >>>>>> >>>>>> Not at the moment because we let the user override >>>>>> own_cpus. >>>>> >>>>> Do we check whether the user's input is valid (match the PMU's cpumask) before the override? >>>>> >>>>> I think we know the PMU name. The cpumask of the PMU can be found in the sysfs. So we should have enough information for a sanity check. >>>> >>>> For the uncore PMU case, I am not sure what sanity is :-) >>>> >>> >>> For a non-core PMU, e.g., uncore, cstate, power and etc. The cpumask is under the /sys/devices/<PMU>/cpumask. It shows the cpumask which kernel supports. If a end user request a different CPU other that the cpumask, I think it's better throw a waning. It should mitigate the confusion which Namhyung mentioned (uncore -C1,2). >> >> So you couldn't get uncore events unless you are also coincidentally wanting to trace CPU 0. >> >> I guess really the requrement is not to perf_event_open() an uncore PMU more than once? >> To figure that out we'd need to be able map CPUs to uncore PMUs? > > We might just use evsel->own_cpus for uncore events and > if the user-given cpu list contains other cpus it can show an > warning. >
Yes, it sounds reasonable.
Thanks, Kan
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