linux-kernel - Re: [PATCH v1 50/51] perf stat: Use counts rather than saved

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Date:   Fri, 24 Feb 2023 14:48:07 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        Sandipan Das <sandipan.das@....com>,
        James Clark <james.clark@....com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        John Garry <john.g.garry@...cle.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Eduard Zingerman <eddyz87@...il.com>,
        Suzuki Poulouse <suzuki.poulose@....com>,
        Leo Yan <leo.yan@...aro.org>,
        Florian Fischer <florian.fischer@...q.space>,
        Ravi Bangoria <ravi.bangoria@....com>,
        Jing Zhang <renyu.zj@...ux.alibaba.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org,
        Perry Taylor <perry.taylor@...el.com>,
        Caleb Biggers <caleb.biggers@...el.com>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v1 50/51] perf stat: Use counts rather than saved_value

On Sun, Feb 19, 2023 at 01:28:47AM -0800, Ian Rogers wrote:
> Switch the hard coded metrics to use the aggregate value rather than
> from saved_value. When computing a metric like IPC the aggregate count
> comes from instructions then cycles is looked up and if present IPC
> computed. Rather than lookup from the saved_value rbtree, search the
> counter's evlist for the desired counter.
> 
> A new helper evsel__stat_type is used to both quickly find a metric
> function and to identify when a counter is the one being sought. So
> that both total and miss counts can be sought, the stat_type enum is
> expanded. The ratio functions are rewritten to share a common helper
> with the ratios being directly passed rather than computed from an
> enum value.
> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
[SNIP]
> -static double runtime_stat_avg(enum stat_type type, int aggr_idx,
> -			       struct runtime_stat_data *rsd)
> +static double find_stat(const struct evsel *evsel, int aggr_idx, enum stat_type type)
>  {
> -	struct saved_value *v;
> -
> -	v = saved_value_lookup(NULL, aggr_idx, false, type, rsd->ctx, rsd->cgrp);
> -	if (!v)
> -		return 0.0;
> -
> -	return avg_stats(&v->stats);
> +	const struct evsel *cur;
> +	int evsel_ctx = evsel_context(evsel);
> +
> +	evlist__for_each_entry(evsel->evlist, cur) {
> +		struct perf_stat_aggr *aggr;
> +
> +		/* Ignore the evsel that is being searched from. */
> +		if (evsel == cur)
> +			continue;
> +
> +		/* Ignore evsels that are part of different groups. */
> +		if (evsel->core.leader->nr_members &&
> +		    evsel->core.leader != cur->core.leader)

The evsel->nr_members is somewhat confusing in that it counts itself
as a member.  I'm not sure it resets the nr_members to 0 for standalone
events.  You'd better checking nr_members greater than 1 for group
events.

Thanks,
Namhyung


> +			continue;
> +		/* Ignore evsels with mismatched modifiers. */
> +		if (evsel_ctx != evsel_context(cur))
> +			continue;
> +		/* Ignore if not the cgroup we're looking for. */
> +		if (evsel->cgrp != cur->cgrp)
> +			continue;
> +		/* Ignore if not the stat we're looking for. */
> +		if (type != evsel__stat_type(cur))
> +			continue;
> +
> +		aggr = &cur->stats->aggr[aggr_idx];
> +		if (type == STAT_NSECS)
> +			return aggr->counts.val;
> +		return aggr->counts.val * cur->scale;
> +	}
> +	return 0.0;
>  }