maybe fixed cpu fork logging

run_all_experiments.sh

@@ -39,6 +39,13 @@ sample_process_csv() {
   local start_uptime="$3"
   local max_seconds="$4"
 
+  local have_pidstat=0
+  if command -v pidstat >/dev/null 2>&1; then
+    have_pidstat=1
+  else
+    log "pidstat not found; install sysstat for accurate CPU sampling"
+  fi
+
   while kill -0 "$pid" 2>/dev/null; do
     local now_uptime elapsed_s
     now_uptime=$(awk '{print $1}' /proc/uptime)
@@ -65,7 +72,7 @@ sample_process_csv() {
     proc_count=$(count_processes || echo 0)
     thread_total=$(count_threads_total || echo 0)
 
-    # Use ps directly to avoid zero deltas for very short-lived processes.
+    # Use pidstat for CPU and ps for memory/thread metrics.
     local cpu rss vsz nlwp
     if command -v ps >/dev/null 2>&1; then
       read -r cpu rss vsz nlwp < <(ps -o %cpu=,rss=,vsz=,nlwp= -p "$pid" 2>/dev/null || echo "0 0 0 0")
@@ -73,14 +80,17 @@ sample_process_csv() {
       rss=${rss:-0}
       vsz=${vsz:-0}
       nlwp=${nlwp:-0}
-      # Some busybox builds scale %CPU by 100.
-      cpu=$(awk -v c="$cpu" 'BEGIN{ if (c>1000) printf "%.2f", c/100; else printf "%.2f", c }')
     else
-      cpu=0.00
       rss=0
       vsz=0
       nlwp=0
     fi
+    if [ "$have_pidstat" -eq 1 ]; then
+      cpu=$(pidstat -p "$pid" 1 1 2>/dev/null | awk -v p="$pid" '$1 ~ /^[0-9]/ && $3==p {print $8; exit}')
+      cpu=${cpu:-0.00}
+    else
+      cpu=0.00
+    fi
     local stk=0 heap=0
 
     printf "%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s\n" \