[tip: core/rcu] torture: Add more tracing crib notes to kvm.sh

[tip-bot2 for Paul E. McKenney]

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     9ccba350bd824ecacbfd8965f4f3ac980b96f951
Gitweb:        https://git.kernel.org/tip/9ccba350bd824ecacbfd8965f4f3ac980b96f951
Author:        Paul E. McKenney <paulmck@xxxxxxxxxx>
AuthorDate:    Tue, 16 Jun 2020 11:16:18 -07:00
Committer:     Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Mon, 29 Jun 2020 12:01:45 -07:00

torture: Add more tracing crib notes to kvm.sh

This commit adds a few more hints about how to use tracing as comments
at the end of kvm.sh.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 tools/testing/selftests/rcutorture/bin/kvm.sh | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/rcutorture/bin/kvm.sh b/tools/testing/selftests/rcutorture/bin/kvm.sh
index 3578c85..bdfa0c0 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm.sh
@@ -503,3 +503,7 @@ fi
 # Tracing: trace_event=rcu:rcu_grace_period,rcu:rcu_future_grace_period,rcu:rcu_grace_period_init,rcu:rcu_nocb_wake,rcu:rcu_preempt_task,rcu:rcu_unlock_preempted_task,rcu:rcu_quiescent_state_report,rcu:rcu_fqs,rcu:rcu_callback,rcu:rcu_kfree_callback,rcu:rcu_batch_start,rcu:rcu_invoke_callback,rcu:rcu_invoke_kfree_callback,rcu:rcu_batch_end,rcu:rcu_torture_read,rcu:rcu_barrier
 # Function-graph tracing: ftrace=function_graph ftrace_graph_filter=sched_setaffinity,migration_cpu_stop
 # Also --kconfig "CONFIG_FUNCTION_TRACER=y CONFIG_FUNCTION_GRAPH_TRACER=y"
+# Control buffer size: --bootargs trace_buf_size=3k
+# Get trace-buffer dumps on all oopses: --bootargs ftrace_dump_on_oops
+# Ditto, but dump only the oopsing CPU: --bootargs ftrace_dump_on_oops=orig_cpu
+# Heavy-handed way to also dump on warnings: --bootargs panic_on_warn