diff --git a/scripts/perf.sh b/scripts/perf.sh
index c3ee231..18d1bb2 100755
--- a/scripts/perf.sh
+++ b/scripts/perf.sh
@@ -9,6 +9,10 @@ ARGS="$@"
 echo "Running as $(whoami)"
 
 HHVM_PID="$(pgrep -xn 'hhvm')"
+PREV_PID=`expr $HHVM_PID - 1`
+if [ ! -f /tmp/perf-$HHVM_PID.map ] && [ -f /tmp/perf-$PREV_PID.map ]; then
+    HHVM_PID=$PREV_PID
+fi
 OSS_DIR=$(pwd)
 
 echo "The first arg is the output directory."