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Date:   Mon, 6 Nov 2023 16:53:35 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Namhyung Kim <namhyung@kernel.org>
Cc:     Jiri Olsa <jolsa@kernel.org>, Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-perf-users@vger.kernel.org,
        Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Subject: Re: [PATCH 1/5] perf annotate: Split struct cycles_info
Message-ID: <ZUlEP9pP3JiSxDVc@kernel.org>
References: <20231103191907.54531-1-namhyung@kernel.org>
 <20231103191907.54531-2-namhyung@kernel.org>
 <ZUk/27WMwtnQPggF@kernel.org>
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Em Mon, Nov 06, 2023 at 04:34:51PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Fri, Nov 03, 2023 at 12:19:03PM -0700, Namhyung Kim escreveu:
> > The cycles info is used only when branch stack is provided.  Split them
> > into a separate struct and lazy allocate them to save some memory.
> > 
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> >  tools/perf/ui/browsers/annotate.c |  2 +-
> >  tools/perf/util/annotate.c        | 34 ++++++++++++++++++-------------
> >  tools/perf/util/annotate.h        | 14 ++++++++-----
> >  3 files changed, 30 insertions(+), 20 deletions(-)
> > 
> > diff --git a/tools/perf/ui/browsers/annotate.c b/tools/perf/ui/browsers/annotate.c
> > index ccdb2cd11fbf..d2470f87344d 100644
> > --- a/tools/perf/ui/browsers/annotate.c
> > +++ b/tools/perf/ui/browsers/annotate.c
> > @@ -337,7 +337,7 @@ static void annotate_browser__calc_percent(struct annotate_browser *browser,
> >  				max_percent = percent;
> >  		}
> >  
> > -		if (max_percent < 0.01 && pos->al.ipc == 0) {
> > +		if (max_percent < 0.01 && (!pos->al.cycles || pos->al.cycles->ipc == 0)) {
> >  			RB_CLEAR_NODE(&pos->al.rb_node);
> >  			continue;
> >  		}
> > diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
> > index 82956adf9963..3e7f75827270 100644
> > --- a/tools/perf/util/annotate.c
> > +++ b/tools/perf/util/annotate.c
> > @@ -1100,8 +1100,8 @@ static void annotation__count_and_fill(struct annotation *notes, u64 start, u64
> >  		for (offset = start; offset <= end; offset++) {
> >  			struct annotation_line *al = notes->offsets[offset];
> >  
> > -			if (al && al->ipc == 0.0) {
> > -				al->ipc = ipc;
> > +			if (al && al->cycles && al->cycles->ipc == 0.0) {
> > +				al->cycles->ipc = ipc;
> >  				cover_insn++;
> >  			}
> >  		}
> > @@ -1134,13 +1134,18 @@ void annotation__compute_ipc(struct annotation *notes, size_t size)
> >  		if (ch && ch->cycles) {
> >  			struct annotation_line *al;
> >  
> > +			al = notes->offsets[offset];
> > +			if (al && al->cycles == NULL) {
> > +				al->cycles = zalloc(sizeof(*al->cycles));
> > +				if (al->cycles == NULL)
> 
> Shouldn't we stop here and tell the user that his system is really tight
> on memory instead of just ignoring it?
> 
> 	if (al->cycles == NULL) {
> 		ui__error("Not enough memory for allocating branch stack cycles info!\n");
> 		return ... its a void function :-\
> 	}
> 
> Since its a void function, can't we detect that we need al->cycles
> allocated at the tool start and allocate it there, then propagate back
> the error?
> 
> Its per line, so doing it lazily is indeed easier, so make that function
> return an error and bail out when not being able to calculate the ipc
> for the remaining lines?

I.e. with this folded into this patch, all but one of the callers of
symbol__annotate2() already call a ui error messagem for instance:

                err = symbol__annotate2(ms, evsel, opts, &browser.arch);
                if (err) {
                        char msg[BUFSIZ];
                        dso->annotate_warned = true;
                        symbol__strerror_disassemble(ms, err, msg, sizeof(msg));
                        ui__error("Couldn't annotate %s:\n%s", sym->name, msg);

- Arnaldo

diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index 3e7f758272703554..99ff3bb9cad8daa6 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -1114,12 +1114,13 @@ static void annotation__count_and_fill(struct annotation *notes, u64 start, u64
 	}
 }
 
-void annotation__compute_ipc(struct annotation *notes, size_t size)
+static int annotation__compute_ipc(struct annotation *notes, size_t size)
 {
+	int err = 0;
 	s64 offset;
 
 	if (!notes->src || !notes->src->cycles_hist)
-		return;
+		return 0;
 
 	notes->total_insn = annotation__count_insn(notes, 0, size - 1);
 	notes->hit_cycles = 0;
@@ -1137,8 +1138,10 @@ void annotation__compute_ipc(struct annotation *notes, size_t size)
 			al = notes->offsets[offset];
 			if (al && al->cycles == NULL) {
 				al->cycles = zalloc(sizeof(*al->cycles));
-				if (al->cycles == NULL)
-					continue;
+				if (al->cycles == NULL) {
+					err = ENOMEM;
+					break;
+				}
 			}
 			if (ch->have_start)
 				annotation__count_and_fill(notes, ch->start, offset, ch);
@@ -1150,7 +1153,21 @@ void annotation__compute_ipc(struct annotation *notes, size_t size)
 			notes->have_cycles = true;
 		}
 	}
+
+	if (err) {
+		while (++offset < (s64)size) {
+			struct cyc_hist *ch = &notes->src->cycles_hist[offset];
+
+			if (ch && ch->cycles) {
+				struct annotation_line *al = notes->offsets[offset];
+				if (al)
+					zfree(&al->cycles);
+			}
+		}
+	}
+
 	annotation__unlock(notes);
+	return 0;
 }
 
 int addr_map_symbol__inc_samples(struct addr_map_symbol *ams, struct perf_sample *sample,
@@ -3270,7 +3287,11 @@ int symbol__annotate2(struct map_symbol *ms, struct evsel *evsel,
 
 	annotation__set_offsets(notes, size);
 	annotation__mark_jump_targets(notes, sym);
-	annotation__compute_ipc(notes, size);
+
+	err = annotation__compute_ipc(notes, size);
+	if (err)
+		goto out_free_offsets;
+
 	annotation__init_column_widths(notes, sym);
 	notes->nr_events = nr_pcnt;
 
diff --git a/tools/perf/util/annotate.h b/tools/perf/util/annotate.h
index 16d27952fd5c1b47..19bc2f03917575a8 100644
--- a/tools/perf/util/annotate.h
+++ b/tools/perf/util/annotate.h
@@ -329,7 +329,6 @@ static inline bool annotation_line__filter(struct annotation_line *al, struct an
 }
 
 void annotation__set_offsets(struct annotation *notes, s64 size);
-void annotation__compute_ipc(struct annotation *notes, size_t size);
 void annotation__mark_jump_targets(struct annotation *notes, struct symbol *sym);
 void annotation__update_column_widths(struct annotation *notes);
 void annotation__init_column_widths(struct annotation *notes, struct symbol *sym);