From: Veronika Molnarova <vmolnaro@redhat.com> The test has been failing for some time when two separate runs of perf benchmarks are recorded for cycles events and their counts are compared, while once the recording was done with option --bpf-counters and once without it. It is expected that the count of the samples should be within a certain range, firstly the difference was set to be within 10%, which was then later raised to 20%. However, the test case keeps failing on certain architectures as recording the provided benchmark can produce completely different counts based on the current load of the system. Sampling two separate runs on intel-eaglestream-spr-13 of "perf stat --no-big-num -e cycles -- perf bench sched messaging -g 1 -l 100 -t": Performance counter stats for 'perf bench sched messaging -g 1 -l 100 -t': 396782898 cycles 0.010051983 seconds time elapsed 0.008664000 seconds user 0.097058000 seconds sys Performance counter stats for 'perf bench sched messaging -g 1 -l 100 -t': 1431133032 cycles 0.021803714 seconds time elapsed 0.023377000 seconds user 0.349918000 seconds sys , which is ranging from 400mil to 1400mil samples. Instead of recording the cycles use instructions event, which provides more stable values. At the same time change the tested workload to one of the provided testing workloads by perf that is not based on a scheduler, which can provide another dependency on the current load. Sampling instructions event with the new workload provide much more stable results on intel-eaglestream-spr-13 of "perf stat --no-big-num -e instructions -- perf test -w brstack": Performance counter stats for 'perf test -w brstack': 64584494 instructions 0.009173945 seconds time elapsed 0.007262000 seconds user 0.002071000 seconds sys Performance counter stats for 'perf test -w brstack': 64672669 instructions 0.008888135 seconds time elapsed 0.005018000 seconds user 0.004018000 seconds sys Signed-off-by: Veronika Molnarova <vmolnaro@redhat.com> Acked-by: Namhyung Kim <namhyung@kernel.org> Cc: mpetlan@redhat.com Signed-off-by: Namhyung Kim <namhyung@kernel.org> Link: https://lore.kernel.org/r/20240625092001.10909-1-vmolnaro@redhat.com --- tools/perf/tests/shell/stat_bpf_counters.sh | 36 ++++++++++----------- 1 file changed, 18 insertions(+), 18 deletions(-) diff --git a/tools/perf/tests/shell/stat_bpf_counters.sh b/tools/perf/tests/shell/stat_bpf_counters.sh index ac1035a56e05..892ddccae1e0 100755 --- a/tools/perf/tests/shell/stat_bpf_counters.sh +++ b/tools/perf/tests/shell/stat_bpf_counters.sh @@ -4,7 +4,7 @@ set -e -workload="perf bench sched messaging -g 1 -l 100 -t" +workload="perf test -w brstack" # check whether $2 is within +/- 10% of $1 compare_number() @@ -25,15 +25,15 @@ compare_number() check_counts() { - base_cycles=$1 - bpf_cycles=$2 + base_instructions=$1 + bpf_instructions=$2 - if [ "$base_cycles" = "<not" ]; then - echo "Skipping: cycles event not counted" + if [ "$base_instructions" = "<not" ]; then + echo "Skipping: instructions event not counted" exit 2 fi - if [ "$bpf_cycles" = "<not" ]; then - echo "Failed: cycles not counted with --bpf-counters" + if [ "$bpf_instructions" = "<not" ]; then + echo "Failed: instructions not counted with --bpf-counters" exit 1 fi } @@ -41,29 +41,29 @@ check_counts() test_bpf_counters() { printf "Testing --bpf-counters " - base_cycles=$(perf stat --no-big-num -e cycles -- $workload 2>&1 | awk '/cycles/ {print $1}') - bpf_cycles=$(perf stat --no-big-num --bpf-counters -e cycles -- $workload 2>&1 | awk '/cycles/ {print $1}') - check_counts $base_cycles $bpf_cycles - compare_number $base_cycles $bpf_cycles + base_instructions=$(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 $bpf_instructions echo "[Success]" } test_bpf_modifier() { printf "Testing bpf event modifier " - stat_output=$(perf stat --no-big-num -e cycles/name=base_cycles/,cycles/name=bpf_cycles/b -- $workload 2>&1) - base_cycles=$(echo "$stat_output"| awk '/base_cycles/ {print $1}') - bpf_cycles=$(echo "$stat_output"| awk '/bpf_cycles/ {print $1}') - check_counts $base_cycles $bpf_cycles - compare_number $base_cycles $bpf_cycles + stat_output=$(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 echo "[Success]" } # skip if --bpf-counters is not supported -if ! perf stat -e cycles --bpf-counters true > /dev/null 2>&1; then +if ! perf stat -e instructions --bpf-counters true > /dev/null 2>&1; then if [ "$1" = "-v" ]; then echo "Skipping: --bpf-counters not supported" - perf --no-pager stat -e cycles --bpf-counters true || true + perf --no-pager stat -e instructions --bpf-counters true || true fi exit 2 fi -- 2.34.1