Messages in this thread | | | Date | Wed, 28 Sep 2022 10:53:49 +0300 | Subject | Re: [PATCH 2/5] libperf: Propagate maps only if necessary | From | Adrian Hunter <> |
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On 27/09/22 20:28, Namhyung Kim wrote: > Hi Adrian, > > On Tue, Sep 27, 2022 at 12:06 AM Adrian Hunter <adrian.hunter@intel.com> wrote: >> >> On 24/09/22 19:57, Namhyung Kim wrote: >>> The current code propagate evsel's cpu map settings to evlist when it's >>> added to an evlist. But the evlist->all_cpus and each evsel's cpus will >>> be updated in perf_evlist__set_maps() later. No need to do it before >>> evlist's cpus are set actually. >>> >>> Actually we discarded this intermediate all_cpus maps at the beginning >>> of perf_evlist__set_maps(). Let's not do this. It's only needed when >>> an evsel is added after the evlist cpu maps are set. >> >> That might not be true. Consider evlist__fix_hybrid_cpus() which fiddles >> with evsel->core.cpus and evsel->core.own_cpus after the evsel has been >> added to the evlist. It can also remove an evsel from the evlist. > > Thanks for your review. I think it's fine to change evsel cpus or to remove > an evsel from evlist before calling evlist__create_maps(). The function > will take care of setting evlist's all_cpus from the evsels in the evlist. > So previous changes in evsel/cpus wouldn't be any special. > > After this point, adding a new evsel needs to update evlist all cpus by > propagating cpu maps. So I think hybrid cpus should be fine. > Did I miss something?
I wondered how it might play out if evlist__fix_hybrid_cpus() reduced the cpus from the target->cpu_list (using perf record -C) , since after this patch all_cpus always starts with the target->cpu_list instead of an empty list. But then, in the hybrid case, it puts a dummy event that uses the target cpu list anyway, so the result is the same.
I don't know if there are any cases where all_cpus would actually need to exclude some of the cpus from target->cpu_list.
> >> >> There might be other cases like that, but that was just one that stuck >> out. > > Thanks for sharing your concern. Please let me know if you could > come up with another. > > Namhyung
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