lkml.org 
[lkml]   [2014]   [Mar]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 2/3] nohz: Move full nohz kick to its own IPI
Date
Now that we have smp_queue_function_single() which can be used to
safely queue IPIs when interrupts are disabled and without worrying
about concurrent callers, lets use it for the full dynticks kick to
notify a CPU that it's exiting single task mode.

This unbloats a bit the scheduler IPI that the nohz code was abusing
for its cool "callable anywhere/anytime" properties.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jens Axboe <axboe@fb.com>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
include/linux/tick.h | 2 ++
kernel/sched/core.c | 5 +----
kernel/sched/sched.h | 2 +-
kernel/time/tick-sched.c | 20 ++++++++++++++++++++
4 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/include/linux/tick.h b/include/linux/tick.h
index b84773c..9d3fcc2 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -182,6 +182,7 @@ static inline bool tick_nohz_full_cpu(int cpu)
extern void tick_nohz_init(void);
extern void __tick_nohz_full_check(void);
extern void tick_nohz_full_kick(void);
+extern void tick_nohz_full_kick_cpu(int cpu);
extern void tick_nohz_full_kick_all(void);
extern void __tick_nohz_task_switch(struct task_struct *tsk);
#else
@@ -190,6 +191,7 @@ static inline bool tick_nohz_full_enabled(void) { return false; }
static inline bool tick_nohz_full_cpu(int cpu) { return false; }
static inline void __tick_nohz_full_check(void) { }
static inline void tick_nohz_full_kick(void) { }
+static inline void tick_nohz_full_kick_cpu(int cpu) { }
static inline void tick_nohz_full_kick_all(void) { }
static inline void __tick_nohz_task_switch(struct task_struct *tsk) { }
#endif
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 0cca04a..a07c3a4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1502,9 +1502,7 @@ void scheduler_ipi(void)
*/
preempt_fold_need_resched();

- if (llist_empty(&this_rq()->wake_list)
- && !tick_nohz_full_cpu(smp_processor_id())
- && !got_nohz_idle_kick())
+ if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
return;

/*
@@ -1521,7 +1519,6 @@ void scheduler_ipi(void)
* somewhat pessimize the simple resched case.
*/
irq_enter();
- tick_nohz_full_check();
sched_ttwu_pending();

/*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index c2119fd..3b165c1 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1233,7 +1233,7 @@ static inline void inc_nr_running(struct rq *rq)
if (tick_nohz_full_cpu(rq->cpu)) {
/* Order rq->nr_running write against the IPI */
smp_wmb();
- smp_send_reschedule(rq->cpu);
+ tick_nohz_full_kick_cpu(rq->cpu);
}
}
#endif
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 9f8af69..33a0043 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -230,6 +230,26 @@ void tick_nohz_full_kick(void)
irq_work_queue(&__get_cpu_var(nohz_full_kick_work));
}

+static DEFINE_PER_CPU(struct queue_single_data, nohz_full_kick_qsd);
+
+static void nohz_full_kick_queue(struct queue_single_data *qsd)
+{
+ __tick_nohz_full_check();
+}
+
+void tick_nohz_full_kick_cpu(int cpu)
+{
+ if (!tick_nohz_full_cpu(cpu))
+ return;
+
+ if (cpu == smp_processor_id()) {
+ irq_work_queue(&__get_cpu_var(nohz_full_kick_work));
+ } else {
+ smp_queue_function_single(cpu, nohz_full_kick_queue,
+ &per_cpu(nohz_full_kick_qsd, cpu));
+ }
+}
+
static void nohz_full_kick_ipi(void *info)
{
__tick_nohz_full_check();
--
1.8.3.1


\
 
 \ /
  Last update: 2014-03-19 20:01    [W:0.032 / U:0.188 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site