linux-kernel - Re: [PATCH v2 01/43] perf stat: Disable TopdownL1 on hybrid

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Date:   Fri, 28 Apr 2023 09:31:30 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Ian Rogers <irogers@...gle.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ahmad Yasin <ahmad.yasin@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Stephane Eranian <eranian@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Perry Taylor <perry.taylor@...el.com>,
        Samantha Alt <samantha.alt@...el.com>,
        Caleb Biggers <caleb.biggers@...el.com>,
        Weilin Wang <weilin.wang@...el.com>,
        Edward Baker <edward.baker@...el.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Florian Fischer <florian.fischer@...q.space>,
        Rob Herring <robh@...nel.org>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        John Garry <john.g.garry@...cle.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Sumanth Korikkar <sumanthk@...ux.ibm.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Leo Yan <leo.yan@...aro.org>,
        Yang Jihong <yangjihong1@...wei.com>,
        James Clark <james.clark@....com>,
        Suzuki Poulouse <suzuki.poulose@....com>,
        Kang Minchul <tegongkang@...il.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 01/43] perf stat: Disable TopdownL1 on hybrid



On 2023-04-28 3:37 a.m., Ian Rogers wrote:
> Bugs with event parsing, event grouping and metrics causes the
> TopdownL1 metricgroup to crash the perf command. Temporarily disable
> the group if no events/metrics are spcecified.
> 

I think it's OK to only disable the metric for perf stat default
temporarily on hybrid as a workaround for 6.4.
Now, the only problem is the default of perf stat on pre-icl in 6.4.

> Signed-off-by: Ian Rogers <irogers@...gle.com>

Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>

Arnaldo, could you please back port this for 6.4 as well?

Thanks,
Kan
> ---
>  tools/perf/builtin-stat.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index efda63f6bf32..be9677aa642f 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -1885,7 +1885,12 @@ static int add_default_attributes(void)
>  		 * Add TopdownL1 metrics if they exist. To minimize
>  		 * multiplexing, don't request threshold computation.
>  		 */
> -		if (metricgroup__has_metric("TopdownL1") &&
> +		/*
> +		 * TODO: TopdownL1 is disabled on hybrid CPUs to avoid a crashes
> +		 * caused by exposing latent bugs. This is fixed properly in:
> +		 * https://lore.kernel.org/lkml/bff481ba-e60a-763f-0aa0-3ee53302c480@linux.intel.com/
> +		 */
> +		if (metricgroup__has_metric("TopdownL1") && !perf_pmu__has_hybrid() &&
>  		    metricgroup__parse_groups(evsel_list, "TopdownL1",
>  					    /*metric_no_group=*/false,
>  					    /*metric_no_merge=*/false,
> @@ -1894,6 +1899,7 @@ static int add_default_attributes(void)
>  					    stat_config.system_wide,
>  					    &stat_config.metric_events) < 0)
>  			return -1;
> +
>  		/* Platform specific attrs */
>  		if (evlist__add_default_attrs(evsel_list, default_null_attrs) < 0)
>  			return -1;