linux-kernel - Re: [PATCH 08/30] perf tools: Propagate cpu maps through the evlist

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Message-ID: <20150615193418.GG5845@kernel.org>
Date:	Mon, 15 Jun 2015 16:34:18 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Jiri Olsa <jolsa@...nel.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Andi Kleen <ak@...ux.intel.com>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 08/30] perf tools: Propagate cpu maps through the evlist

Em Sun, Jun 14, 2015 at 10:19:23AM +0200, Jiri Olsa escreveu:
> Propagate evlist's cpu_map object through all the evsel objects,
> while keeping already configured evsel->cpus.
> 
> It'll be handy to access evsel's cpus directly
> in following patches.
> 
> Link: http://lkml.kernel.org/n/tip-myadl53clbkjvzeqolwp95w0@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  tools/perf/util/evlist.c | 24 +++++++++++++++++++++++-
>  1 file changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index f7d80ca58136..c0d3058c1868 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -1085,6 +1085,28 @@ int perf_evlist__mmap(struct perf_evlist *evlist, unsigned int pages,
>  	return perf_evlist__mmap_ex(evlist, pages, overwrite, 0, false);
>  }
>  
> +static int propagate_maps(struct perf_evlist *evlist, struct target *target)

Please rename this to perf_evlist__set_maps()

> +{
> +	struct perf_evsel *evsel;

> +	evlist__for_each(evlist, evsel) {
> +		/*
> +		 * We already have cpus for evsel (via PMU sysfs) so

                   If we already...

> +		 * keep it, if there's no target cpu list defined.
                          ^ The comma here confused me
> +		 */
> +		if (evsel->cpus && target->cpu_list)
> +			cpu_map__put(evsel->cpus);

If you drop the reference, and then will test it... use a
cpu_map__zput(&evsel->cpus), so that after the put you don't access
something you don't hold a reference for anymore...

But the logic is still confusing! Can you try to rewrite it in a more
clear way? 

> +		if (!evsel->cpus || target->cpu_list)
> +			evsel->cpus = cpu_map__get(evlist->cpus);

Something like:

		if (evsel->cpus) {
			something
		} else {
			something else
		}
> +
> +		if (!evsel->cpus)
> +			return -ENOMEM;

Where was that we tried to allocate memory in this operation?

> +	}
> +
> +	return 0;
> +}
> +
>  int perf_evlist__create_maps(struct perf_evlist *evlist, struct target *target)
>  {
>  	evlist->threads = thread_map__new_str(target->pid, target->tid,
> @@ -1101,7 +1123,7 @@ int perf_evlist__create_maps(struct perf_evlist *evlist, struct target *target)
>  	if (evlist->cpus == NULL)
>  		goto out_delete_threads;
>  
> -	return 0;
> +	return propagate_maps(evlist, target);
>  
>  out_delete_threads:
>  	thread_map__put(evlist->threads);
> -- 
> 1.9.3
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