[PATCH 32/32] nohz, not for merge: Add tickless tracing

[Steven Rostedt]

From: Frederic Weisbecker <fweis...@gmail.com>

add hoc tickless tracing

Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
---
 arch/x86/kernel/smp.c    |    2 ++
 kernel/cpuset.c          |    1 +
 kernel/time/tick-sched.c |    7 +++++++
 3 files changed, 10 insertions(+)

diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index 0bad72d..45f2176 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -264,6 +264,7 @@ finish:
 void smp_reschedule_interrupt(struct pt_regs *regs)
 {
        ack_APIC_irq();
+       trace_printk("IPI: Scheduler\n");
        inc_irq_stat(irq_resched_count);
        scheduler_ipi();
        /*
@@ -276,6 +277,7 @@ void smp_cpuset_update_nohz_interrupt(struct pt_regs *regs)
 {
        ack_APIC_irq();
        irq_enter();
+       trace_printk("IPI: Nohz update\n");
        tick_nohz_check_adaptive();
        inc_irq_stat(irq_call_count);
        irq_exit();
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 218abc8..84f099c 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1212,6 +1212,7 @@ static cpumask_t nohz_cpuset_mask;
 
 static void flush_cputime_interrupt(void *unused)
 {
+       trace_printk("IPI: flush cputime\n");
        tick_nohz_flush_current_times(false);
 }
 
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index bdd40bb..db19c2d 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -376,6 +376,7 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched 
*ts,
                if (!ts->tick_stopped) {
                        ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
                        ts->tick_stopped = 1;
+                       trace_printk("Stop tick\n");
                }
 
                /*
@@ -581,6 +582,7 @@ static void tick_nohz_cpuset_stop_tick(struct tick_sched 
*ts)
 
                ts->saved_jiffies = jiffies;
                set_thread_flag(TIF_NOHZ);
+               trace_printk("set TIF_NOHZ\n");
        }
 }
 #else
@@ -659,6 +661,7 @@ static void __tick_nohz_restart_sched_tick(struct 
tick_sched *ts, ktime_t now)
        ts->idle_exittime = now;
 
        tick_nohz_restart(ts, now);
+       trace_printk("Restart sched tick\n");
 }
 
 /**
@@ -1012,6 +1015,7 @@ static void tick_nohz_restart_adaptive(void)
        tick_nohz_flush_current_times(true);
        tick_nohz_restart_sched_tick();
        clear_thread_flag(TIF_NOHZ);
+       trace_printk("clear TIF_NOHZ\n");
        tick_nohz_cpu_exit_qs();
 }
 
@@ -1031,6 +1035,7 @@ void cpuset_exit_nohz_interrupt(void *unused)
 {
        struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
 
+       trace_printk("IPI: Nohz exit\n");
        if (ts->tick_stopped && !is_idle_task(current))
                tick_nohz_restart_adaptive();
 }
@@ -1052,6 +1057,7 @@ void tick_nohz_pre_schedule(void)
        if (test_thread_flag(TIF_NOHZ)) {
                tick_nohz_flush_current_times(true);
                clear_thread_flag(TIF_NOHZ);
+               trace_printk("clear TIF_NOHZ\n");
                /* FIXME: warn if we are in RCU idle mode */
        }
 }
@@ -1147,6 +1153,7 @@ static enum hrtimer_restart tick_sched_timer(struct 
hrtimer *timer)
                }
                update_process_times(user);
                profile_tick(CPU_PROFILING);
+               trace_printk("tick\n");
        }
 
        hrtimer_forward(timer, now, tick_period);
-- 
1.7.10.4


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