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Date:   Mon, 11 Dec 2023 18:13:10 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     kan.liang@linux.intel.com
Cc:     irogers@google.com, namhyung@kernel.org, mark.rutland@arm.com,
        maz@kernel.org, marcan@marcan.st, linux-kernel@vger.kernel.org,
        linux-perf-users@vger.kernel.org
Subject: Re: [PATCH] perf top: Use evsel's cpus to replace user_requested_cpus
Message-ID: <ZXd7ZuxbNNsjAyqm@kernel.org>
References: <20231208210855.407580-1-kan.liang@linux.intel.com>
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Em Fri, Dec 08, 2023 at 01:08:55PM -0800, kan.liang@linux.intel.com escreveu:
> From: Kan Liang <kan.liang@linux.intel.com>
> 
> perf top errors out on a hybrid machine
>  $perf top
> 
>  Error:
>  The cycles:P event is not supported.
> 
> The user_requested_cpus may contain CPUs that are invalid for a hybrid
> PMU. It causes perf_event_open to fail.

?

All perf top expects is that the "cycles", the most basic one, be
collected, on all CPUs in the system.

> The commit ef91871c960e ("perf evlist: Propagate user CPU maps
> intersecting core PMU maps") already intersect the requested CPU map
> with the CPU map of the PMU. Use the evsel's cpus to replace
> user_requested_cpus.
 
> The evlist's threads is also propagated to evsel's threads in
> __perf_evlist__propagate_maps(). Replace it as well.

Thanks, but please try to add more detail to the fix so as to help
others to consider looking at the patch.

- Arnaldo
 
> Reported-by: Arnaldo Carvalho de Melo <acme@kernel.org>
> Closes: https://lore.kernel.org/linux-perf-users/ZXNnDrGKXbEELMXV@kernel.org/
> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
> ---
>  tools/perf/builtin-top.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
> index ea8c7eca5eee..cce9350177e2 100644
> --- a/tools/perf/builtin-top.c
> +++ b/tools/perf/builtin-top.c
> @@ -1027,8 +1027,8 @@ static int perf_top__start_counters(struct perf_top *top)
>  
>  	evlist__for_each_entry(evlist, counter) {
>  try_again:
> -		if (evsel__open(counter, top->evlist->core.user_requested_cpus,
> -				     top->evlist->core.threads) < 0) {
> +		if (evsel__open(counter, counter->core.cpus,
> +				counter->core.threads) < 0) {
>  
>  			/*
>  			 * Specially handle overwrite fall back.
> -- 
> 2.35.1
> 

-- 

- Arnaldo