sched/deadline: Add latency tracing for SCHED_DEADLINE tasks

It is very likely that systems that wants/needs to use the new
SCHED_DEADLINE policy also want to have the scheduling latency of
the -deadline tasks under control.

For this reason a new version of the scheduling wakeup latency,
called "wakeup_dl", is introduced.

As a consequence of applying this patch there will be three wakeup
latency tracer:

 * "wakeup", that deals with all tasks in the system;
 * "wakeup_rt", that deals with -rt and -deadline tasks only;
 * "wakeup_dl", that deals with -deadline tasks only.

Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1383831828-15501-9-git-send-email-juri.lelli@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 19 insertions, 14 deletions

diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index a7329b7902f8..e98fca60974f 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -1022,11 +1022,16 @@ trace_selftest_startup_nop(struct tracer *trace, struct trace_array *tr)
 #ifdef CONFIG_SCHED_TRACER
 static int trace_wakeup_test_thread(void *data)
 {
-        /* Make this a RT thread, doesn't need to be too high */
-        static const struct sched_param param = { .sched_priority = 5 };
+        /* Make this a -deadline thread */
+        static const struct sched_attr attr = {
+                .sched_policy = SCHED_DEADLINE,
+                .sched_runtime = 100000ULL,
+                .sched_deadline = 10000000ULL,
+                .sched_period = 10000000ULL
+        };
         struct completion *x = data;
 
-        sched_setscheduler(current, SCHED_FIFO, &param);
+        sched_setattr(current, &attr);
 
         /* Make it know we have a new prio */
         complete(x);
@@ -1040,8 +1045,8 @@ static int trace_wakeup_test_thread(void *data)
         /* we are awake, now wait to disappear */
         while (!kthread_should_stop()) {
                 /*
-                 * This is an RT task, do short sleeps to let
-                 * others run.
+                 * This will likely be the system top priority
+                 * task, do short sleeps to let others run.
                  */
                 msleep(100);
         }
@@ -1054,21 +1059,21 @@ trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
 {
         unsigned long save_max = tracing_max_latency;
         struct task_struct *p;
-        struct completion isrt;
+        struct completion is_ready;
         unsigned long count;
         int ret;
 
-        init_completion(&isrt);
+        init_completion(&is_ready);
 
-        /* create a high prio thread */
-        p = kthread_run(trace_wakeup_test_thread, &isrt, "ftrace-test");
+        /* create a -deadline thread */
+        p = kthread_run(trace_wakeup_test_thread, &is_ready, "ftrace-test");
         if (IS_ERR(p)) {
                 printk(KERN_CONT "Failed to create ftrace wakeup test thread ");
                 return -1;
         }
 
-        /* make sure the thread is running at an RT prio */
-        wait_for_completion(&isrt);
+        /* make sure the thread is running at -deadline policy */
+        wait_for_completion(&is_ready);
 
         /* start the tracing */
         ret = tracer_init(trace, tr);
@@ -1082,19 +1087,19 @@ trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
 
         while (p->on_rq) {
                 /*
-                 * Sleep to make sure the RT thread is asleep too.
+                 * Sleep to make sure the -deadline thread is asleep too.
                  * On virtual machines we can't rely on timings,
                  * but we want to make sure this test still works.
                  */
                 msleep(100);
         }
 
-        init_completion(&isrt);
+        init_completion(&is_ready);
 
         wake_up_process(p);
 
         /* Wait for the task to wake up */
-        wait_for_completion(&isrt);
+        wait_for_completion(&is_ready);
 
         /* stop the tracing. */
         tracing_stop();