[PATCH v2] perf test: Fix perf stat --bpf-counters on hybrid machines

[Ian Rogers]

Events on hardware PMUs may open on >1 hardware PMU on hybrid
machines. Unfortunately multiplexing introduces a scaling issue as
reported in:
https://lore.kernel.org/lkml/20250716223924.825772-1-irogers@xxxxxxxxxx/

Switch to using task-clock which as a software event runs on all CPUs
and has a single PMU.

For when hybrid event scaling is fixed, incorporate support for
combining hybrid counts as posted by Namhyung Kim in:
https://lore.kernel.org/lkml/20260319064513.9269-1-namhyung@xxxxxxxxxx/

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
Acked-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
v1: https://lore.kernel.org/lkml/20260323202409.194123-1-irogers@xxxxxxxxxx/
---
 tools/perf/tests/shell/stat_bpf_counters.sh | 55 ++++++++++++++-------
 1 file changed, 38 insertions(+), 17 deletions(-)

diff --git a/tools/perf/tests/shell/stat_bpf_counters.sh b/tools/perf/tests/shell/stat_bpf_counters.sh
index f43e28a136d3..f8c24ccc7830 100755
--- a/tools/perf/tests/shell/stat_bpf_counters.sh
+++ b/tools/perf/tests/shell/stat_bpf_counters.sh
@@ -5,6 +5,24 @@
 set -e
 
 workload="perf test -w sqrtloop"
+event=task-clock
+
+extract_count()
+{
+	local target_event="$1"
+
+	awk -v target="$target_event" -v i=0 -v c=0 '
+	$0 ~ target {
+		i++;
+		c += $1
+	}
+	END {
+		if (i > 0)
+			printf "%.0f\n", c;
+		else
+			print "<not counted>"
+	}'
+}
 
 # check whether $2 is within +/- 20% of $1
 compare_number()
@@ -25,15 +43,15 @@ compare_number()
 
 check_counts()
 {
-	base_instructions=$1
-	bpf_instructions=$2
+	base_count=$1
+	bpf_count=$2
 
-	if [ "$base_instructions" = "<not" ]; then
-		echo "Skipping: instructions event not counted"
+	if [ "$base_count" = "<not counted>" ]; then
+		echo "Skipping: $event event not counted"
 		exit 2
 	fi
-	if [ "$bpf_instructions" = "<not" ]; then
-		echo "Failed: instructions not counted with --bpf-counters"
+	if [ "$bpf_count" = "<not counted>" ]; then
+		echo "Failed: $event not counted with --bpf-counters"
 		exit 1
 	fi
 }
@@ -41,29 +59,32 @@ check_counts()
 test_bpf_counters()
 {
 	printf "Testing --bpf-counters "
-	base_instructions=$(perf stat --no-big-num -e instructions -- $workload 2>&1 | awk '/instructions/ {print $1}')
-	bpf_instructions=$(perf stat --no-big-num --bpf-counters -e instructions -- $workload  2>&1 | awk '/instructions/ {print $1}')
-	check_counts $base_instructions $bpf_instructions
-	compare_number $base_instructions $bpf_instructions
+	base_count=$(perf stat --no-big-num -e "$event" -- $workload 2>&1 \
+          | extract_count "$event")
+	bpf_count=$(perf stat --no-big-num --bpf-counters -e "$event" -- $workload  2>&1 \
+          | extract_count "$event")
+	check_counts "$base_count" "$bpf_count"
+	compare_number "$base_count" "$bpf_count"
 	echo "[Success]"
 }
 
 test_bpf_modifier()
 {
 	printf "Testing bpf event modifier "
-	stat_output=$(perf stat --no-big-num -e instructions/name=base_instructions/,instructions/name=bpf_instructions/b -- $workload 2>&1)
-	base_instructions=$(echo "$stat_output"| awk '/base_instructions/ {print $1}')
-	bpf_instructions=$(echo "$stat_output"| awk '/bpf_instructions/ {print $1}')
-	check_counts $base_instructions $bpf_instructions
-	compare_number $base_instructions $bpf_instructions
+	stat_output=$(perf stat --no-big-num \
+          -e "$event/name=base_$event/,$event/name=bpf_$event/b" -- $workload 2>&1)
+	base_count=$(echo "$stat_output" | extract_count "base_$event")
+	bpf_count=$(echo "$stat_output"|  extract_count "bpf_$event")
+	check_counts "$base_count" "$bpf_count"
+	compare_number "$base_count" "$bpf_count"
 	echo "[Success]"
 }
 
 # skip if --bpf-counters is not supported
-if ! perf stat -e instructions --bpf-counters true > /dev/null 2>&1; then
+if ! perf stat -e "$event" --bpf-counters true > /dev/null 2>&1; then
 	if [ "$1" = "-v" ]; then
 		echo "Skipping: --bpf-counters not supported"
-		perf --no-pager stat -e instructions --bpf-counters true || true
+		perf --no-pager stat -e "$event" --bpf-counters true || true
 	fi
 	exit 2
 fi
-- 
2.53.0.1018.g2bb0e51243-goog