linux-kernel - Re: [BUG] perf report --pid not reporting correctly

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Date:   Wed, 21 Sep 2016 18:34:53 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:     Stephane Eranian <eranian@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Namhyung Kim <namhyung@...nel.org>,
        "mingo@...e.hu" <mingo@...e.hu>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        Vince Weaver <vincent.weaver@...ne.edu>, acme@...nel.org
Subject: Re: [BUG] perf report --pid not reporting correctly

On Wed, Sep 21, 2016 at 12:37:53PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Sep 20, 2016 at 06:29:59PM -0700, Stephane Eranian escreveu:
> > Hi Arnaldo,
> > 
> > I ran into an issue trying to use the --pid filtering option of perf report.
> > 
> > I do a system-wide collection and then I want to narrow down the
> > reporting to a specific process:
> > 
> > $ perf record -a -e cycles:pp sleep 10
> > $ perf report --sort cpu,comm --pid X
> > 
> > Where X is a process sampled during the run (easy to catch with perf report -D)
> > If you do it this way, it works, but if you do:
> > 
> > $ perf report --sort cpu --pid X
> > 
> > Then you get an empty output.
> > 
> > I suspect it has to do with the way hist entries are added to the
> > histogram and aggregated. If the first event for a sort criteria is
> > not coming from pid X, it will
> > still be added in the histogram. if pid X aggregates to the same
> > sample criteria, then you will lose the pid information. And then
> > later when you try to apply the filter,
> > it will mark the hist entry as FILTERED because it does not have a matching pid
> > and nothing will be printed.
> > I suspect you want to apply the filtering upfront for pid. It will
> > only add to the histograms matching samples. It changes the
> > percentages you will see. They will
> > only report the breakdown for the pid.
> > 
> > I have a quick hack to do upfront filtering which does something as
> > follows but I am not sure this is the correct way of doing this.
> > 
> > Let me know what you think.
> 
> From a first look I think this makes sense, i.e. we should do the first
> round of filtering, one that trows away stuff, for things in the command
> line, when creating the histogram entries.
> 
> Later, as we have now, we can apply further filters for non-collapsed
> fields of hist_entry.
> 
> Jiri, Namhyung, are you ok with this?

Stephan is correct with analysis, but I think we need to add both non/filtered
entries in, because we provide that 'F' key for non/filtered counts switch in tui 

how about something like below

thanks,
jirka

---
diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index b02992efb513..659e0357be68 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -536,6 +536,14 @@ static struct hist_entry *hists__findnew_entry(struct hists *hists,
 				map__put(he->ms.map);
 				he->ms.map = map__get(entry->ms.map);
 			}
+
+			/*
+			 * We have at least one entry in which is not
+			 * filtered, we want to display the entry.
+			 */
+			if (he->filtered && !entry->filtered)
+				he->filtered = 0;
+
 			goto out;
 		}