rt-tests: generate latency plot

- Generate a latency plot PNG file in /tmp/latency-plot.png.
- Generate a latency summary file in /tmp/latency-summary.log.

Related-to: TOR-1198
Signed-off-by: Ming Liu <ming.liu@toradex.com>

rt-tests/Dockerfile

@@ -4,7 +4,9 @@ ARG IMAGE_TAG=2-bullseye
 FROM --platform=$IMAGE_ARCH torizon/debian:$IMAGE_TAG
 
 RUN apt-get update \
-    && apt-get install -y --no-install-recommends rt-tests \
+    && apt-get install -y --no-install-recommends gnuplot rt-tests \
     && rm -rf /var/lib/apt/lists/*
 
-CMD ["cyclictest","-S","-p99","-i1000","-m","-D20m", "-q", "|", "tee", "cyclictest.log"]
+COPY rt-tests.sh /rt-tests.sh
+
+CMD ["/rt-tests.sh"]

rt-tests/rt-tests.sh

@@ -0,0 +1,63 @@
+#!/bin/bash
+
+# Run cyclictest
+if ! cyclictest -S -p99 -i1000 -m -D12h -h400 -q >output; then
+  echo "ERROR: cyclictest failed" >&2
+  exit 1
+fi
+
+# Get maximum latency
+max=`grep "Max Latencies" output | tr " " "\n" | sort -n | tail -1 | sed s/^0*//`
+
+# Grep data lines, remove empty lines and create a common field separator
+grep -v -e "^#" -e "^$" output | tr " " "\t" >histogram
+
+# Create two-column data sets with latency classes and frequency values for each core
+cores=$(grep -c ^processor /proc/cpuinfo)
+for i in `seq 1 $cores`
+do
+  column=`expr $i + 1`
+  cut -f1,$column histogram >histogram$i
+done
+
+# Create plot command header
+echo -n -e "set title \"Latency plot\"\n\
+set terminal png\n\
+set xlabel \"Latency (us), max $max us\"\n\
+set logscale y\n\
+set xrange [0:400]\n\
+set yrange [0.8:*]\n\
+set ylabel \"Number of latency samples\"\n\
+set output \"plot.png\"\n\
+plot " >plotcmd
+
+# Append plot command data references
+for i in `seq 1 $cores`
+do
+  if test $i != 1
+  then
+    echo -n ", " >>plotcmd
+  fi
+  cpuno=`expr $i - 1`
+  if test $cpuno -lt 10
+  then
+    title=" CPU$cpuno"
+   else
+    title="CPU$cpuno"
+  fi
+  echo -n "\"histogram$i\" using 1:2 title \"$title\" with histeps" >>plotcmd
+done
+
+# Execute plot command
+gnuplot -persist <plotcmd
+
+# Print summary to /tmp
+echo "Generating latency summary to /tmp/latency-summary.log"
+grep -e "^#" output >/tmp/latency-summary.log
+
+# Copy plot to /tmp/latency-plot.png
+echo "Generating latency plot to /tmp/latency-plot.png"
+cp plot.png /tmp/latency-plot.png
+
+# Clean up
+rm -f histogram* output plotcmd plot.png