Add cpu-limit option for mini-benchmark

As performance improves, the permitted number of CPU cycles to be used
during the benchmark should be lowered to catch performance regressions. An
option is added to better support this.

All new code of the whole pull request, including one or several files that are
either new files or modified ones, are contributed under the BSD-new license. I
am contributing on behalf of my employer Amazon Web Services, Inc.

support-files/mini-benchmark.sh

@@ -26,6 +26,8 @@ display_help() {
   echo "                     sysbench runs"
   echo "  --perf-flamegraph  record performance counters in perf.data.* and"
   echo "                     generate flamegraphs automatically"
+  echo "  --cpu-limit        upper limit on the number of CPU cycles (in billions) used for the benchmark"
+  echo "                     default: 750"
   echo "  -h, --help         display this help and exit"
 }
 
@@ -79,6 +81,11 @@ do
       PERF_RECORD=true
       shift
       ;;
+    --cpu-limit)
+      shift
+      CPU_CYCLE_LIMIT=$1
+      shift
+      ;;
     -*)
       echo "Error: Unknown option: $1" >&2
       ## or call function display_help
@@ -247,12 +254,21 @@ then
   echo "Total: $(grep -h -e instructions sysbench-run-*.log | sort -k 1 | awk '{s+=$1}END{print s}')"
   echo # Newline improves readability
 
+  if [ -z "$CPU_CYCLE_LIMIT" ]
+  then 
+     # 04-04-2024: We found this to be an appropriate default limit after running a few benchmarks
+     # Configure the limit with --cpu-limit if needed
+    CPU_CYCLE_LIMIT=750
+  fi
+  CPU_CYCLE_LIMIT_LONG="${CPU_CYCLE_LIMIT}000000000"
+
   # Final verdict based on cpu cycle count
   RESULT="$(grep -h -e cycles sysbench-run-*.log | sort -k 1 | awk '{s+=$1}END{print s}')"
-  if [ "$RESULT" -gt 850 ]
+  if [ "$RESULT" -gt "$CPU_CYCLE_LIMIT_LONG" ]
   then
     echo # Newline improves readability
-    echo "Benchmark exceeded 850 billion cpu cycles, performance most likely regressed!"
+    echo "Benchmark exceeded the allowed limit of ${CPU_CYCLE_LIMIT} billion CPU cycles"
+    echo "Performance most likely regressed!"
     exit 1
   fi
 fi