perf stat: Document --metric-no-threshold and threshold colors

Document the threshold behavior for -M/--metrics.

Reviewed-by: Kan Liang <[email protected]>
Signed-off-by: Ian Rogers <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Ahmad Yasin <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Caleb Biggers <[email protected]>
Cc: Eduard Zingerman <[email protected]>
Cc: Edward Baker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Perry Taylor <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Samantha Alt <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Weilin Wang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 15 insertions, 0 deletions

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 785f0e2bcfac..8f789fa1242e 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -361,6 +361,15 @@ small group that need not have multiplexing is lowered. This option
 forbids the event merging logic from sharing events between groups and
 may be used to increase accuracy in this case.
 
+--metric-no-threshold::
+Metric thresholds may increase the number of events necessary to
+compute whether a metric has exceeded its threshold expression. This
+may not be desirable, for example, as the events can introduce
+multiplexing. This option disables the adding of threshold expression
+events for a metric. However, if there are sufficient events to
+compute the threshold then the threshold is still computed and used to
+color the metric's computed value.
+
 --quiet::
 Don't print output, warnings or messages. This is useful with perf stat
 record below to only write data to the perf.data file.
@@ -405,6 +414,12 @@ For a group all metrics from the group are added.
 The events from the metrics are automatically measured.
 See perf list output for the possible metrics and metricgroups.
 
+	When threshold information is available for a metric, the
+	color red is used to signify a metric has exceeded a threshold
+	while green shows it hasn't. The default color means that
+	no threshold information was available or the threshold
+	couldn't be computed.
+
 -A::
 --no-aggr::
 Do not aggregate counts across all monitored CPUs.