Add lock contention graph script to openssl

Add a script to use gnuplot to graph lock contention events as reported
by the REPORT_RWLOCK_CONTENTION feature vs time so we can see an
application run time based view of where lock contention occurs.

Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/28974)

diff --git a/util/lock-contention-graph.sh b/util/lock-contention-graph.sh
new file mode 100755 (executable)
index 0000000..e9e252d
--- /dev/null
+++ b/util/lock-contention-graph.sh
@@ -0,0 +1,133 @@
+#!/bin/bash -eu
+# Copyright 2025 The OpenSSL Project Authors. All Rights Reserved.
+#
+# Licensed under the Apache License 2.0 (the "License").
+# You may not use this file except in compliance with the License.
+# You can obtain a copy in the file LICENSE in the source distribution
+# or at https://www.openssl.org/source/license.html
+#
+# Script to graph logs produced by REPORT_RWLOCK_CONTENTION vs time
+# Usage: ./lock-contention-graph.sh <logfile> <labels>
+#
+# Parameters:
+# logfile - output file from REPORT_RWLOCK_CONTENTION
+# labels - optional value to add timestamp markers to contention event edges
+#          for correlation with log file timestamps
+# Output:
+# The displayed graph is plots application run time on the x axis in
+# microseconds, with the y axis representing contention events for each
+# found thread individually as a unit step function.
+#
+# i.e. thread 1 toggles between the values 0 and 1, with 0 representing
+# no contention, and 1 representing waiting on a lock.  Thread 2 is offset
+# on the y axis by 1, toggling between 2 and 3, with the former representing no
+# contention, and 3 representing waiting on a lock to become available.
+###################################################################
+
+TEMPDIR=$(mktemp -d /tmp/contentiongraph.XXXXXX)
+LOGFILE=$1
+LABELS=$2
+
+trap "rm -rf $TEMPDIR" EXIT
+
+if [ ! -f $LOGFILE ]
+then
+    echo "No log file found" > /dev/stderr
+    exit 1
+fi
+LOGFILEBASE=$(basename $LOGFILE)
+
+mkdir -p $TEMPDIR/tids/
+
+#
+# Gather all our tids
+#
+declare -a filelines
+declare -a sorted_lines
+
+declare -a attimes
+declare -a unblocktimes
+declare -a levels
+
+let offset=0
+
+for i in $(cat $LOGFILE | grep "lock blocked" $LOGFILE | awk '{print $12}' | sort | uniq); do
+    filelines=()
+    sorted_lines=()
+    mapfile -t filelines < <(cat $LOGFILE | grep "tid $i")
+    IFS=$'\n' sorted_lines=($(sort -k 10 -n <<<"${filelines[*]}"))
+    unset IFS
+
+    attimes=()
+    unblocktimes=()
+    levels=()
+    rawtime=()
+    let up=$offset+1
+    let down=$offset
+    let firsttime=0
+    echo "Processing tid $i"
+    for LINE in "${sorted_lines[@]}"; do
+        DURATION=$(echo $LINE | awk '{print $6}')
+        ATTIME=$(echo $LINE | awk '{print $10}')
+        UNBLOCKTIME=$(dc -e "$ATTIME $DURATION + p")
+        if [ $firsttime -eq 0 ]; then
+            let firsttime=$ATTIME
+        fi
+        rawtime+=($ATTIME)
+        ATTIME=$(dc -e"$ATTIME $firsttime - p")
+        UNBLOCKTIME=$(dc -e "$UNBLOCKTIME $firsttime - p")
+        attimes+=($ATTIME)
+        levels+=($down)
+        levels+=($up)
+        unblocktimes+=($UNBLOCKTIME)
+        levels+=($up)
+        levels+=($down)
+    done
+
+#
+# Write out our array to a file
+#
+    NUMELEMS=${#attimes[@]}
+    for j in $(seq 0 1 $NUMELEMS); do
+        let lvlidx=$j*4
+        echo "${attimes[$j]} ${levels[$lvlidx]} ${rawtime[$j]}" >> $TEMPDIR/tids/$i.data
+        let lvlidx=$lvlidx+1
+        echo "${attimes[$j]} ${levels[$lvlidx]}" >> $TEMPDIR/tids/$i.data
+        let lvlidx=$lvlidx+1
+        echo "${unblocktimes[$j]} ${levels[$lvlidx]}" >> $TEMPDIR/tids/$i.data
+        let lvlidx=$lvlidx+1
+        echo "${unblocktimes[$j]} ${levels[$lvlidx]}" >> $TEMPDIR/tids/$i.data
+    done
+
+    let offset=$offset+2
+done
+
+#
+# Now lets use gnuplot to plot all the contentions
+#
+cat << EOF > $TEMPDIR/gnuplot.script
+set term qt 
+set format x '%.0f'
+set xlabel "usecs"
+set ylabel "contentions"
+set yrange [0:5]
+set xtics 10000
+set xrange [0:5000000]
+EOF
+
+echo -n "plot " >> $TEMPDIR/gnuplot.script
+
+for i in $(ls $TEMPDIR/tids/*.data)
+do
+    TITLE=$(basename $i)
+    echo -n "\"$i\" using 1:2 with lines title \"tid $TITLE\", " >> $TEMPDIR/gnuplot.script
+    if [ -n "$LABELS" ]; then
+        echo -n "\"$i\" using 1:2:3 with labels offset 0, char 1 notitle, " >> $TEMPDIR/gnuplot.script
+    fi
+done
+
+echo "" >> $TEMPDIR/gnuplot.script
+echo "pause -1" >> $TEMPDIR/gnuplot.script
+
+gnuplot $TEMPDIR/gnuplot.script
+