diff --git a/tools/testing/selftests/ftrace/test.d/event/subsystem-enable.tc b/tools/testing/selftests/ftrace/test.d/event/subsystem-enable.tc
index 83a8c571e93a..ff6cf579f503 100644
--- a/tools/testing/selftests/ftrace/test.d/event/subsystem-enable.tc
+++ b/tools/testing/selftests/ftrace/test.d/event/subsystem-enable.tc
@@ -22,7 +22,7 @@ echo 'sched:*' > set_event
 
 yield
 
-count=`cat trace | grep -v ^# | awk '{ print $5 }' | sort -u | wc -l`
+count=`head -n 100 trace | grep -v ^# | awk '{ print $5 }' | sort -u | wc -l`
 if [ $count -lt 3 ]; then
     fail "at least fork, exec and exit events should be recorded"
 fi
@@ -33,7 +33,7 @@ echo 1 > events/sched/enable
 
 yield
 
-count=`cat trace | grep -v ^# | awk '{ print $5 }' | sort -u | wc -l`
+count=`head -n 100 trace | grep -v ^# | awk '{ print $5 }' | sort -u | wc -l`
 if [ $count -lt 3 ]; then
     fail "at least fork, exec and exit events should be recorded"
 fi
@@ -44,7 +44,7 @@ echo 0 > events/sched/enable
 
 yield
 
-count=`cat trace | grep -v ^# | awk '{ print $5 }' | sort -u | wc -l`
+count=`head -n 100 trace | grep -v ^# | awk '{ print $5 }' | sort -u | wc -l`
 if [ $count -ne 0 ]; then
     fail "any of scheduler events should not be recorded"
 fi