linux-kernel - Re: [PATCH v5 09/13] perf evsel: Support opening on a specific CPU

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Message-ID: <20191112004100.GH573472@tassilo.jf.intel.com>
Date:   Mon, 11 Nov 2019 16:41:00 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Andi Kleen <andi@...stfloor.org>, jolsa@...nel.org,
        acme@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 09/13] perf evsel: Support opening on a specific CPU

On Mon, Nov 11, 2019 at 02:30:33PM +0100, Jiri Olsa wrote:
> On Thu, Nov 07, 2019 at 10:16:42AM -0800, Andi Kleen wrote:
> > From: Andi Kleen <ak@...ux.intel.com>
> 
> SNIP
> 
> >  int perf_evsel__open_per_thread(struct evsel *evsel,
> > diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> > index b10d5ba21966..54513d70c109 100644
> > --- a/tools/perf/util/evsel.h
> > +++ b/tools/perf/util/evsel.h
> > @@ -223,7 +223,8 @@ int evsel__enable(struct evsel *evsel);
> >  int evsel__disable(struct evsel *evsel);
> >  
> >  int perf_evsel__open_per_cpu(struct evsel *evsel,
> > -			     struct perf_cpu_map *cpus);
> > +			     struct perf_cpu_map *cpus,
> > +			     int cpu);
> >  int perf_evsel__open_per_thread(struct evsel *evsel,
> >  				struct perf_thread_map *threads);
> >  int evsel__open(struct evsel *evsel, struct perf_cpu_map *cpus,
> > diff --git a/tools/perf/util/stat.c b/tools/perf/util/stat.c
> > index 6822e4ffe224..36dc95032e4c 100644
> > --- a/tools/perf/util/stat.c
> > +++ b/tools/perf/util/stat.c
> > @@ -517,7 +517,7 @@ int create_perf_stat_counter(struct evsel *evsel,
> >  	}
> >  
> >  	if (target__has_cpu(target) && !target__has_per_thread(target))
> > -		return perf_evsel__open_per_cpu(evsel, evsel__cpus(evsel));
> > +		return perf_evsel__open_per_cpu(evsel, evsel__cpus(evsel), -1);
> 
> how will -1 owrk in here? it will end up as:
> 
>    perf_evsel__open_per_cpu
>     evsel__open_cpu( ...., start_cpu = -1, end_cpu = -1 + 1)
>       for (cpu = start_cpu; cpu < end_cpu; cpu++) {

Yes you're right. The problem was the splitting of the patches.
With the two patches combined it works. So the end result is good,
just a bad intermediate step.

I will merge them again.

It seems better than creating something complicated here that
will just be undone next patch again.

-Andi