[PATCH 06/13] [PATCH 07/13] sched: Add latency tracing for -deadline tasks
From: Peter Zijlstra
Date: Tue Dec 17 2013 - 07:48:07 EST
From: Dario Faggioli <raistlin@xxxxxxxx>
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.
Cc: bruce.ashfield@xxxxxxxxxxxxx
Cc: claudio@xxxxxxxxxxxxxxx
Cc: darren@xxxxxxxxxx
Cc: dhaval.giani@xxxxxxxxx
Cc: fchecconi@xxxxxxxxx
Cc: fweisbec@xxxxxxxxx
Cc: harald.gustafsson@xxxxxxxxxxxx
Cc: hgu1972@xxxxxxxxx
Cc: insop.song@xxxxxxxxx
Cc: jkacur@xxxxxxxxxx
Cc: johan.eker@xxxxxxxxxxxx
Cc: liming.wang@xxxxxxxxxxxxx
Cc: luca.abeni@xxxxxxxx
Cc: michael@xxxxxxxxxxxxxxxxxxxx
Cc: mingo@xxxxxxxxxx
Cc: nicola.manica@xxxxxxxxxxxxx
Cc: oleg@xxxxxxxxxx
Cc: paulmck@xxxxxxxxxxxxxxxxxx
Cc: p.faure@xxxxxxxxxx
Cc: rostedt@xxxxxxxxxxx
Cc: tglx@xxxxxxxxxxxxx
Cc: tommaso.cucinotta@xxxxxxxx
Cc: vincent.guittot@xxxxxxxxxx
Signed-off-by: Dario Faggioli <raistlin@xxxxxxxx>
Signed-off-by: Juri Lelli <juri.lelli@xxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
---
kernel/trace/trace_sched_wakeup.c | 64 ++++++++++++++++++++++++++++++++++---
kernel/trace/trace_selftest.c | 32 +++++++++++--------
2 files changed, 78 insertions(+), 18 deletions(-)
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index fee77e1..090c4d9 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -27,6 +27,8 @@ static int wakeup_cpu;
static int wakeup_current_cpu;
static unsigned wakeup_prio = -1;
static int wakeup_rt;
+static int wakeup_dl;
+static int tracing_dl = 0;
static arch_spinlock_t wakeup_lock =
(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
@@ -437,6 +439,7 @@ static void __wakeup_reset(struct trace_array *tr)
{
wakeup_cpu = -1;
wakeup_prio = -1;
+ tracing_dl = 0;
if (wakeup_task)
put_task_struct(wakeup_task);
@@ -472,9 +475,17 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
tracing_record_cmdline(p);
tracing_record_cmdline(current);
- if ((wakeup_rt && !rt_task(p)) ||
- p->prio >= wakeup_prio ||
- p->prio >= current->prio)
+ /*
+ * Semantic is like this:
+ * - wakeup tracer handles all tasks in the system, independently
+ * from their scheduling class;
+ * - wakeup_rt tracer handles tasks belonging to sched_dl and
+ * sched_rt class;
+ * - wakeup_dl handles tasks belonging to sched_dl class only.
+ */
+ if (tracing_dl || (wakeup_dl && !dl_task(p)) ||
+ (wakeup_rt && !dl_task(p) && !rt_task(p)) ||
+ (!dl_task(p) && (p->prio >= wakeup_prio || p->prio >= current->prio)))
return;
pc = preempt_count();
@@ -486,7 +497,8 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
arch_spin_lock(&wakeup_lock);
/* check for races. */
- if (!tracer_enabled || p->prio >= wakeup_prio)
+ if (!tracer_enabled || tracing_dl ||
+ (!dl_task(p) && p->prio >= wakeup_prio))
goto out_locked;
/* reset the trace */
@@ -496,6 +508,15 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
wakeup_current_cpu = wakeup_cpu;
wakeup_prio = p->prio;
+ /*
+ * Once you start tracing a -deadline task, don't bother tracing
+ * another task until the first one wakes up.
+ */
+ if (dl_task(p))
+ tracing_dl = 1;
+ else
+ tracing_dl = 0;
+
wakeup_task = p;
get_task_struct(wakeup_task);
@@ -597,16 +618,25 @@ static int __wakeup_tracer_init(struct trace_array *tr)
static int wakeup_tracer_init(struct trace_array *tr)
{
+ wakeup_dl = 0;
wakeup_rt = 0;
return __wakeup_tracer_init(tr);
}
static int wakeup_rt_tracer_init(struct trace_array *tr)
{
+ wakeup_dl = 0;
wakeup_rt = 1;
return __wakeup_tracer_init(tr);
}
+static int wakeup_dl_tracer_init(struct trace_array *tr)
+{
+ wakeup_dl = 1;
+ wakeup_rt = 0;
+ return __wakeup_tracer_init(tr);
+}
+
static void wakeup_tracer_reset(struct trace_array *tr)
{
int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
@@ -674,6 +704,28 @@ static struct tracer wakeup_rt_tracer __read_mostly =
.use_max_tr = true,
};
+static struct tracer wakeup_dl_tracer __read_mostly =
+{
+ .name = "wakeup_dl",
+ .init = wakeup_dl_tracer_init,
+ .reset = wakeup_tracer_reset,
+ .start = wakeup_tracer_start,
+ .stop = wakeup_tracer_stop,
+ .wait_pipe = poll_wait_pipe,
+ .print_max = true,
+ .print_header = wakeup_print_header,
+ .print_line = wakeup_print_line,
+ .flags = &tracer_flags,
+ .set_flag = wakeup_set_flag,
+ .flag_changed = wakeup_flag_changed,
+#ifdef CONFIG_FTRACE_SELFTEST
+ .selftest = trace_selftest_startup_wakeup,
+#endif
+ .open = wakeup_trace_open,
+ .close = wakeup_trace_close,
+ .use_max_tr = true,
+};
+
__init static int init_wakeup_tracer(void)
{
int ret;
@@ -686,6 +738,10 @@ __init static int init_wakeup_tracer(void)
if (ret)
return ret;
+ ret = register_tracer(&wakeup_dl_tracer);
+ if (ret)
+ return ret;
+
return 0;
}
core_initcall(init_wakeup_tracer);
diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index a7329b7..542de6a 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -1022,11 +1022,15 @@ 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_runtime = 100000ULL,
+ .sched_deadline = 10000000ULL,
+ .sched_period = 10000000ULL
+ };
struct completion *x = data;
- sched_setscheduler(current, SCHED_FIFO, ¶m);
+ sched_setscheduler2(current, SCHED_DEADLINE, &attr);
/* Make it know we have a new prio */
complete(x);
@@ -1040,8 +1044,8 @@ 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 +1058,21 @@ 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 +1086,19 @@ 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();
--
1.7.10.4
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