lkml.org 
[lkml]   [2023]   [Dec]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: 'perf top' broken on intel hybrid systems
On Sat, Dec 9, 2023 at 9:26 PM Ian Rogers <irogers@google.com> wrote:
>
> On Sat, Dec 9, 2023, 12:14 PM Leah Neukirchen <leah@vuxu.org> wrote:
>>
>>
>> > The error is because the perf top always tries to open an event on the
>> > user_requested_cpus, which are all CPUs by default.
>> >
>> > Something as below should fix it. For hybrid, open a PMU event on an
>> > unsupported CPU should be error out.
>> >
>> > diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
>>
>> This fixes "perf top" on my i7-1355U. It would be great if you could
>> get this patch into upstream and stable branches.
>
>
>
> I'll try to take a look ASAP. As we don't need this for record there is some existing logic that perf top is clearly missing. We should also have a test on perf top.

So for stat and record there is a call to evlist__create_maps:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/builtin-stat.c?h=perf-tools-next#n2730
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/builtin-record.c?h=perf-tools-next#n4210

In evlist__create_maps we do perf_evlist__propagate_maps and that will:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/lib/perf/evlist.c?h=perf-tools-next#n43
```
} else if (evlist->has_user_cpus && evsel->is_pmu_core) {
/*
* User requested CPUs on a core PMU, ensure the requested CPUs
* are valid by intersecting with those of the PMU.
*/
perf_cpu_map__put(evsel->cpus);
evsel->cpus = perf_cpu_map__intersect(evlist->user_requested_cpus,
evsel->own_cpus);
```

I think the fix should be looking to do the same map set up in top as
stat and record, presumably there was a refactor and top was
overlooked. I'll try to address this and add a basic sanity test of
doing a few iterations of perf top on stdio, which would have been
sufficient to catch this.

Thanks,
Ian

\
 
 \ /
  Last update: 2023-12-11 18:24    [W:0.052 / U:0.120 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site