linux-kernel - Re: [PATCH v2 0/2] perf tools: annotation browser from c2c tui

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Message-ID: <20230619071537.GA153131@samus.usersys.redhat.com>
Date:   Mon, 19 Jun 2023 09:15:37 +0200
From:   Artem Savkov <asavkov@...hat.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/2] perf tools: annotation browser from c2c tui

On Wed, Jun 14, 2023 at 03:38:35PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Fri, Jun 09, 2023 at 10:37:31AM +0200, Artem Savkov escreveu:
> > On Thu, Jun 08, 2023 at 02:09:06PM -0700, Namhyung Kim wrote:
> > > Hello,
> > > 
> > > On Thu, Jun 8, 2023 at 1:44 AM Artem Savkov <asavkov@...hat.com> wrote:
> > > >
> > > > These patches add ability to start annotation browser from c2c report
> > > > tui. The idea comes from Arnaldo's "Profiling Data Structures" talk [1].
> > > 
> > > I was thinking about how it works and realized that it didn't collect
> > > samples by symbol.  Then I'm not sure if the result is meaningful.
> > > I think it'd show a random symbol that touched the cache line
> > > first.  The same cache line can be accessed from other locations
> > > but it cannot know where they are.
> > > 
> > > Also different instructions in a function (symbol) would access a
> > > different cache line.  The annotate output just shows any memory
> > > access.  So it might be good to check the instruction at the point
> > > but others should not be considered related.
> > > 
> > > Hmm.. I suspect even the same instruction will hit the different
> > > cache lines at different times.  Then probably the annotation
> > > won't work well in terms of correlating cache lines.
> > 
> > The annotation hotkey is only added to the cacheline detailed view where
> > we do have symbol instruction information. The idea is to give the user
> > ability to quickly jump to source code/disassembly directly from c2c
> > TUI.
> > 
> > The hit percentages in annotation view don't make much sense in this
> > case though, so maybe it is better to use dummy evsel so that none are
> > shown.
> 
> Yes, the point is just to reuse the source browser, if there is no
> annotation data applicable, don't use any.
> 

Ok, should be as easy as the following diff. I'll include it in v3 if
there si more feedback.

---

diff --git b/tools/perf/builtin-c2c.c a/tools/perf/builtin-c2c.c
index dce8604837aec..c856ce7a50740 100644
--- b/tools/perf/builtin-c2c.c
+++ a/tools/perf/builtin-c2c.c
@@ -2701,7 +2701,11 @@ static int perf_c2c__browse_cacheline(struct hist_entry *he)

                switch (key) {
                case 'a':
-                       do_annotate(browser, evlist__first(c2c.evlist));
+                       /*
+                        * We don't need percentage info so use 'dummy:HG'
+                        * evsel which is last in evlist.
+                        */
+                       do_annotate(browser, evlist__last(c2c.evlist));
                        break;
                case 's':
                        c2c.symbol_full = !c2c.symbol_full;