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Date: Wed, 27 Nov 2013 15:19:43 +0100
From: Juri Lelli <juri.lelli@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
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 11/27/2013 03:16 PM, Steven Rostedt wrote:
> 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.
>
Right.
>> };
>> 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.
>
And right.
>>
>> 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.
>
No, indeed.
Thanks,
- Juri
>> +
>> 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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