From 64724095a33fbee805657415a4eb374bef5161c9 Mon Sep 17 00:00:00 2001 From: Aaron Tomlin Date: Sat, 18 Jul 2026 21:38:00 -0400 Subject: [PATCH] perf stat: Add --hide-zero-events option to suppress zero-count events When monitoring a large number of events (e.g., with wildcards such as --event 'syscalls:sys_enter_*'), many matched events will return a count of zero. This clutters the output, making it difficult to spot the active events. Add a new option --hide-zero-events to suppress printing events that have a count of zero. To prevent formatting and diagnostic issues, the zero-skipping logic implements the following rules: 1. In metric-only mode (i.e., --metric-only), columns must remain aligned in the output grid. We evaluate config->metric_only first to avoid skipping zero-valued columns, preventing values from shifting left and aligning under incorrect headers 2. For explicitly requested events, we ensure they are not silently hidden if they are unsupported. We only hide a zero-count event if counter->supported is true, ensuring that unsupported explicit events still report "" Signed-off-by: Aaron Tomlin Reviewed-by: Ian Rogers Signed-off-by: Namhyung Kim --- tools/perf/Documentation/perf-stat.txt | 3 ++ tools/perf/builtin-stat.c | 2 ++ tools/perf/tests/shell/stat.sh | 46 ++++++++++++++++++++++++++ tools/perf/util/stat-display.c | 3 ++ tools/perf/util/stat.h | 1 + 5 files changed, 55 insertions(+) diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt index b72a29c9223c..f334aabdc809 100644 --- a/tools/perf/Documentation/perf-stat.txt +++ b/tools/perf/Documentation/perf-stat.txt @@ -162,6 +162,9 @@ null run - Don't start any counters. This can be useful to measure just elapsed wall-clock time - or to assess the raw overhead of perf stat itself, without running any counters. +--hide-zero-events:: +Do not show events with a zero count. + -v:: --verbose:: be more verbose (show counter open errors, etc) diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index a85a4f30221a..d68a2617a920 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -2505,6 +2505,8 @@ int cmd_stat(int argc, const char **argv) "display details about each run (only with -r option)"), OPT_BOOLEAN('n', "null", &stat_config.null_run, "null run - dont start any counters"), + OPT_BOOLEAN(0, "hide-zero-events", &stat_config.hide_zero, + "Do not show events with a zero count"), OPT_INCR('d', "detailed", &detailed_run, "detailed run - start a lot of events"), OPT_BOOLEAN('S', "sync", &sync_run, diff --git a/tools/perf/tests/shell/stat.sh b/tools/perf/tests/shell/stat.sh index 649de1166fed..298ce454b45a 100755 --- a/tools/perf/tests/shell/stat.sh +++ b/tools/perf/tests/shell/stat.sh @@ -546,6 +546,51 @@ test_csv_json_fail() { fi } +test_hide_zero_events_stat() { + echo "Hide zero events stat test" + if ! perf stat -e context-switches,cpu-migrations true > "${stat_output}" 2>&1 + then + echo "Hide zero events stat test [Skipped event parsing failed]" + return + fi + + zero_event="" + if grep -q -E "[[:space:]]+0[[:space:]]+context-switches" "${stat_output}"; then + zero_event="context-switches" + elif grep -q -E "[[:space:]]+0[[:space:]]+cpu-migrations" "${stat_output}"; then + zero_event="cpu-migrations" + fi + + if [ -z "$zero_event" ]; then + echo "Hide zero events stat test [Skipped - no zero count event found]" + return + fi + + if ! perf stat --hide-zero-events -e context-switches,cpu-migrations true > "${stat_output}" 2>&1 + then + echo "Hide zero events stat test [Failed - command failed]" + err=1 + return + fi + + if grep -q -E "$zero_event" "${stat_output}" + then + echo "Hide zero events stat test [Failed - zero event $zero_event was not hidden]" + err=1 + return + fi + + # Check that --metric-only works with --hide-zero-events + if ! perf stat --hide-zero-events --metric-only -e instructions,cycles true > "${stat_output}" 2>&1 + then + echo "Hide zero events stat test [Failed - metric-only command failed]" + err=1 + return + fi + + echo "Hide zero events stat test [Success]" +} + test_default_stat test_null_stat test_offline_cpu_stat @@ -563,6 +608,7 @@ test_stat_repeat test_stat_pid test_stat_delay test_csv_json_fail +test_hide_zero_events_stat cleanup exit $err diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c index f94f1324d24a..b337cc23f413 100644 --- a/tools/perf/util/stat-display.c +++ b/tools/perf/util/stat-display.c @@ -907,6 +907,9 @@ static bool should_skip_zero_counter(struct perf_stat_config *config, /* Metric only counts won't be displayed but the metric wants to be computed. */ if (config->metric_only) return false; + + if (config->hide_zero && counter->supported) + return true; /* * Skip value 0 when enabling --per-thread globally, * otherwise it will have too many 0 output. diff --git a/tools/perf/util/stat.h b/tools/perf/util/stat.h index 4bced233d2fc..e3598037a6aa 100644 --- a/tools/perf/util/stat.h +++ b/tools/perf/util/stat.h @@ -69,6 +69,7 @@ struct perf_stat_config { bool interval_clear; bool metric_only; bool null_run; + bool hide_zero; bool ru_display; bool big_num; bool hybrid_merge;