lkml.org 
[lkml]   [2010]   [Feb]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[RFC][PATCH 07/11] sched: add latency tracing for -deadline tasks.
From
Date
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>
---
kernel/trace/trace_sched_wakeup.c | 44 +++++++++++++++++++++++++++++++++---
kernel/trace/trace_selftest.c | 30 +++++++++++++++----------
2 files changed, 58 insertions(+), 16 deletions(-)

diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 0271742..a02ce04 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -27,6 +27,7 @@ static int wakeup_cpu;
static int wakeup_current_cpu;
static unsigned wakeup_prio = -1;
static int wakeup_rt;
+static int wakeup_dl;

static arch_spinlock_t wakeup_lock =
(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
@@ -214,9 +215,17 @@ probe_wakeup(struct rq *rq, 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 ((wakeup_dl && !dl_task(p)) ||
+ (wakeup_rt && !dl_task(p) && !rt_task(p)) ||
+ (p->prio >= wakeup_prio || p->prio >= current->prio))
return;

pc = preempt_count();
@@ -228,7 +237,7 @@ probe_wakeup(struct rq *rq, struct task_struct *p, int success)
arch_spin_lock(&wakeup_lock);

/* check for races. */
- if (!tracer_enabled || p->prio >= wakeup_prio)
+ if (!tracer_enabled || (!dl_task(p) && p->prio >= wakeup_prio))
goto out_locked;

/* reset the trace */
@@ -340,16 +349,25 @@ 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)
{
stop_wakeup_tracer(tr);
@@ -398,6 +416,20 @@ static struct tracer wakeup_rt_tracer __read_mostly =
#endif
};

+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 = 1,
+#ifdef CONFIG_FTRACE_SELFTEST
+ .selftest = trace_selftest_startup_wakeup,
+#endif
+};
+
__init static int init_wakeup_tracer(void)
{
int ret;
@@ -410,6 +442,10 @@ __init static int init_wakeup_tracer(void)
if (ret)
return ret;

+ ret = register_tracer(&wakeup_dl_tracer);
+ if (ret)
+ return ret;
+
return 0;
}
device_initcall(init_wakeup_tracer);
diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index 280fea4..4834411 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -558,11 +558,17 @@ 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 */
- struct sched_param param = { .sched_priority = 5 };
+ /* Make this a -deadline thread */
+ struct sched_param param = { .sched_priority = 0 };
+ struct sched_param_ex paramx = {
+ .sched_priority = 0,
+ .sched_runtime = { .tv_sec = 0, .tv_nsec = 100000 },
+ .sched_deadline = { .tv_sec = 0, .tv_nsec = 10000000 },
+ .sched_flags = 0
+ };
struct completion *x = data;

- sched_setscheduler(current, SCHED_FIFO, &param);
+ sched_setscheduler_ex(current, SCHED_DEADLINE, &param, &paramx);

/* Make it know we have a new prio */
complete(x);
@@ -574,8 +580,8 @@ 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);
}
@@ -588,21 +594,21 @@ 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);
@@ -614,7 +620,7 @@ trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
/* reset the max latency */
tracing_max_latency = 0;

- /* sleep to let the RT thread sleep too */
+ /* sleep to let the thread sleep too */
msleep(100);

/*
--
1.7.0
--
<<This happens because I choose it to happen!>> (Raistlin Majere)
----------------------------------------------------------------------
Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa (Italy)
http://blog.linux.it/raistlin / raistlin@ekiga.net /
dario.faggioli@jabber.org
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2010-02-28 20:25    [W:0.098 / U:1.512 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site