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Message-ID: <9a35e6b66b3d106860945962faf1a6858c8ccf17.camel@intel.com>
Date: Tue, 15 Oct 2024 16:53:07 +0000
From: "Falcon, Thomas" <thomas.falcon@...el.com>
To: "namhyung@...nel.org" <namhyung@...nel.org>, "acme@...nel.org"
<acme@...nel.org>, "james.clark@...aro.org" <james.clark@...aro.org>,
"linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
"irogers@...gle.com" <irogers@...gle.com>
CC: "alexander.shishkin@...ux.intel.com" <alexander.shishkin@...ux.intel.com>,
"peterz@...radead.org" <peterz@...radead.org>, "mark.rutland@....com"
<mark.rutland@....com>, "mingo@...hat.com" <mingo@...hat.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Hunter,
Adrian" <adrian.hunter@...el.com>, "kan.liang@...ux.intel.com"
<kan.liang@...ux.intel.com>, "jolsa@...nel.org" <jolsa@...nel.org>
Subject: Re: [RFC PATCH 1/1] libperf: evlist: Fix --cpu argument on hybrid
platform
On Tue, 2024-10-15 at 15:54 +0100, James Clark wrote:
> Since the linked fixes: commit, specifying a CPU on hybrid platforms
> results in an error because Perf tries to open an extended type event
> on "any" CPU which isn't valid. Extended type events can only be
> opened
> on CPUs that match the type.
>
> Before (working):
>
> $ perf record --cpu 1 -- true
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 2.385 MB perf.data (7 samples) ]
>
> After (not working):
>
> $ perf record -C 1 -- true
> WARNING: A requested CPU in '1' is not supported by PMU 'cpu_atom'
> (CPUs 16-27) for event 'cycles:P'
> Error:
> The sys_perf_event_open() syscall returned with 22 (Invalid
> argument) for event (cpu_atom/cycles:P/).
> /bin/dmesg | grep -i perf may provide additional information.
>
> (Ignore the warning message, that's expected and not particularly
> relevant to this issue).
>
> This is because perf_cpu_map__intersect() of the user specified CPU
> (1)
> and one of the PMU's CPUs (16-27) correctly results in an empty
> (NULL)
> CPU map. However for the purposes of opening an event, libperf
> converts
> empty CPU maps into an any CPU (-1) which the kernel rejects.
>
> Fix it by deleting evsels with empty CPU maps in the specific case
> where
> user requested CPU maps are evaluated.
>
> Fixes: 251aa040244a ("perf parse-events: Wildcard most "numeric"
> events")
> Signed-off-by: James Clark <james.clark@...aro.org>
Works for me on an i9-12900.
Tested-by: Thomas Falcon <thomas.falcon@...el.com>
Thanks
> ---
> tools/lib/perf/evlist.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c
> index c6d67fc9e57e..8fae9a157a91 100644
> --- a/tools/lib/perf/evlist.c
> +++ b/tools/lib/perf/evlist.c
> @@ -47,6 +47,13 @@ static void __perf_evlist__propagate_maps(struct
> perf_evlist *evlist,
> */
> perf_cpu_map__put(evsel->cpus);
> evsel->cpus = perf_cpu_map__intersect(evlist-
> >user_requested_cpus, evsel->own_cpus);
> +
> + /*
> + * Empty cpu lists would eventually get opened as
> "any" so remove
> + * genuinely empty ones before they're opened in the
> wrong place.
> + */
> + if (perf_cpu_map__is_empty(evsel->cpus))
> + perf_evlist__remove(evlist, evsel);
> } else if (!evsel->own_cpus || evlist->has_user_cpus ||
> (!evsel->requires_cpu &&
> perf_cpu_map__has_any_cpu(evlist->user_requested_cpus))) {
> /*
> @@ -80,11 +87,11 @@ static void __perf_evlist__propagate_maps(struct
> perf_evlist *evlist,
>
> static void perf_evlist__propagate_maps(struct perf_evlist *evlist)
> {
> - struct perf_evsel *evsel;
> + struct perf_evsel *evsel, *n;
>
> evlist->needs_map_propagation = true;
>
> - perf_evlist__for_each_evsel(evlist, evsel)
> + list_for_each_entry_safe(evsel, n, &evlist->entries, node)
> __perf_evlist__propagate_maps(evlist, evsel);
> }
>
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