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Date: Wed, 27 Nov 2013 09:16:47 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Juri Lelli <juri.lelli@...il.com>
Cc: peterz@...radead.org, tglx@...utronix.de, mingo@...hat.com,
oleg@...hat.com, fweisbec@...il.com, darren@...art.com,
johan.eker@...csson.com, p.faure@...tech.ch,
linux-kernel@...r.kernel.org, claudio@...dence.eu.com,
michael@...rulasolutions.com, fchecconi@...il.com,
tommaso.cucinotta@...up.it, nicola.manica@...i.unitn.it,
luca.abeni@...tn.it, dhaval.giani@...il.com, hgu1972@...il.com,
paulmck@...ux.vnet.ibm.com, raistlin@...ux.it,
insop.song@...il.com, liming.wang@...driver.com, jkacur@...hat.com,
harald.gustafsson@...csson.com, vincent.guittot@...aro.org,
bruce.ashfield@...driver.com
Subject: Re: [PATCH 08/14] sched: add latency tracing for -deadline tasks.
On Wed, 27 Nov 2013 14:43:45 +0100
Juri Lelli <juri.lelli@...il.com> wrote:
diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
> index f76f8d6..ad94604 100644
> --- a/kernel/trace/trace_selftest.c
> +++ b/kernel/trace/trace_selftest.c
> @@ -1023,16 +1023,16 @@ trace_selftest_startup_nop(struct tracer *trace, struct trace_array *tr)
> static int trace_wakeup_test_thread(void *data)
> {
> /* Make this a -deadline thread */
> - struct sched_param2 paramx = {
> + static const struct sched_param2 param = {
> .sched_priority = 0,
> + .sched_flags = 0,
> .sched_runtime = 100000ULL,
> .sched_deadline = 10000000ULL,
> .sched_period = 10000000ULL
> - .sched_flags = 0
Assigning structures like this, you don't need to set the zero fields.
all fields not explicitly stated, are set to zero.
> };
> struct completion *x = data;
>
>
> --------------------------------
> kernel/trace/trace_sched_wakeup.c | 28 ++++++++++++++++++++++++----
> 1 file changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
> index 1457fb1..090c4d9 100644
> --- a/kernel/trace/trace_sched_wakeup.c
> +++ b/kernel/trace/trace_sched_wakeup.c
> @@ -28,6 +28,7 @@ static int wakeup_current_cpu;
> static unsigned wakeup_prio = -1;
> static int wakeup_rt;
> static int wakeup_dl;
> +static int tracing_dl = 0;
Get rid of the ' = 0', its implicit to all static and global variables
that are not given any value.
>
> static arch_spinlock_t wakeup_lock =
> (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
> @@ -438,6 +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);
> @@ -481,9 +483,9 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
> * sched_rt class;
> * - wakeup_dl handles tasks belonging to sched_dl class only.
> */
> - if ((wakeup_dl && !dl_task(p)) ||
> + if (tracing_dl || (wakeup_dl && !dl_task(p)) ||
> (wakeup_rt && !dl_task(p) && !rt_task(p)) ||
> - (p->prio >= wakeup_prio || p->prio >= current->prio))
> + (!dl_task(p) && (p->prio >= wakeup_prio || p->prio >= current->prio)))
> return;
>
> pc = preempt_count();
> @@ -495,7 +497,8 @@ probe_wakeup(void *ignore, struct task_struct *p, int success)
> arch_spin_lock(&wakeup_lock);
>
> /* check for races. */
> - if (!tracer_enabled || (!dl_task(p) && p->prio >= wakeup_prio))
> + if (!tracer_enabled || tracing_dl ||
> + (!dl_task(p) && p->prio >= wakeup_prio))
> goto out_locked;
>
> /* reset the trace */
> @@ -505,6 +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;
Do we need the else statement? I would think the only way to get here
is if tracing_dl is already set to zero.
-- Steve
> +
> wakeup_task = p;
> get_task_struct(wakeup_task);
>
> @@ -700,10 +712,18 @@ static struct tracer wakeup_dl_tracer __read_mostly =
> .start = wakeup_tracer_start,
> .stop = wakeup_tracer_stop,
> .wait_pipe = poll_wait_pipe,
> - .print_max = 1,
> + .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)
> -----------------------------------
>
> Makes sense? :)
>
> Thanks,
>
> - Juri
--
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