linux-kernel - Re: [PATCH 2/5] perf stat: Add --for-each-cgroup option

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Date:   Tue, 22 Sep 2020 23:40:33 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCH 2/5] perf stat: Add --for-each-cgroup option

On Mon, Sep 21, 2020 at 06:46:07PM +0900, Namhyung Kim wrote:

SNIP

> +int evlist__expand_cgroup(struct evlist *evlist, const char *str)
> +{
> +	struct evlist *orig_list, *tmp_list;
> +	struct evsel *pos, *evsel, *leader;
> +	struct cgroup *cgrp = NULL;
> +	const char *p, *e, *eos = str + strlen(str);
> +	int ret = -1;
> +
> +	if (evlist->core.nr_entries == 0) {
> +		fprintf(stderr, "must define events before cgroups\n");
> +		return -EINVAL;
> +	}
> +
> +	orig_list = evlist__new();
> +	tmp_list = evlist__new();
> +	if (orig_list == NULL || tmp_list == NULL) {
> +		fprintf(stderr, "memory allocation failed\n");
> +		return -ENOMEM;
> +	}
> +
> +	/* save original events and init evlist */
> +	perf_evlist__splice_list_tail(orig_list, &evlist->core.entries);
> +	evlist->core.nr_entries = 0;
> +
> +	for (;;) {
> +		p = strchr(str, ',');
> +		e = p ? p : eos;
> +
> +		/* allow empty cgroups, i.e., skip */
> +		if (e - str) {
> +			/* termination added */
> +			char *name = strndup(str, e - str);
> +			if (!name)
> +				goto out_err;
> +
> +			cgrp = cgroup__new(name);
> +			free(name);
> +			if (cgrp == NULL)
> +				goto out_err;
> +		} else {
> +			cgrp = NULL;
> +		}
> +
> +		leader = NULL;
> +		evlist__for_each_entry(orig_list, pos) {
> +			evsel = evsel__clone(pos);
> +			if (evsel == NULL)
> +				goto out_err;
> +
> +			cgroup__put(evsel->cgrp);
> +			evsel->cgrp = cgroup__get(cgrp);
> +
> +			if (evsel__is_group_leader(pos))
> +				leader = evsel;
> +			evsel->leader = leader;

hum, will this work if there's standalone event after group? like:

  {cycles,instructions},cache-misses

cache-misses will get cycles as group leader no?

jirka

> +
> +			evlist__add(tmp_list, evsel);
> +		}
> +		/* cgroup__new() has a refcount, release it here */
> +		cgroup__put(cgrp);
> +		nr_cgroups++;

SNIP