From: Frederic Weisbecker <fweis...@gmail.com>
Try to give the timekeeing duty to a CPU that doesn't belong
to any nohz cpuset when possible, so that we increase the chance
for these nohz cpusets to run their CPUs out of periodic tick
mode.
[TODO: We need to find a way to ensure there is always one non-nohz
running CPU maintaining the timekeeping duty if every non-idle CPUs are
adaptive tickless]
Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
Cc: Alessio Igor Bogani <abog...@kernel.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Avi Kivity <a...@redhat.com>
Cc: Chris Metcalf <cmetc...@tilera.com>
Cc: Christoph Lameter <c...@linux.com>
Cc: Daniel Lezcano <daniel.lezc...@linaro.org>
Cc: Geoff Levand <ge...@infradead.org>
Cc: Gilad Ben Yossef <gi...@benyossef.com>
Cc: Hakan Akkan <hakanak...@gmail.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Kevin Hilman <khil...@ti.com>
Cc: Max Krasnyansky <m...@qualcomm.com>
Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Stephen Hemminger <shemmin...@vyatta.com>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporat...@gmail.com>
Cc: Thomas Gleixner <t...@linutronix.de>
---
kernel/time/tick-sched.c | 52 ++++++++++++++++++++++++++++++++++++----------
1 file changed, 41 insertions(+), 11 deletions(-)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index d6d16fe..c7a78c6 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -20,6 +20,7 @@
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/module.h>
+#include <linux/cpuset.h>
#include <asm/irq_regs.h>
@@ -789,6 +790,45 @@ void tick_check_idle(int cpu)
tick_check_nohz(cpu);
}
+#ifdef CONFIG_CPUSETS_NO_HZ
+
+/*
+ * Take the timer duty if nobody is taking care of it.
+ * If a CPU already does and and it's in a nohz cpuset,
+ * then take the charge so that it can switch to nohz mode.
+ */
+static void tick_do_timer_check_handler(int cpu)
+{
+ int handler = tick_do_timer_cpu;
+
+ if (unlikely(handler == TICK_DO_TIMER_NONE)) {
+ tick_do_timer_cpu = cpu;
+ } else {
+ if (!cpuset_adaptive_nohz() &&
+ cpuset_cpu_adaptive_nohz(handler))
+ tick_do_timer_cpu = cpu;
+ }
+}
+
+#else
+
+static void tick_do_timer_check_handler(int cpu)
+{
+#ifdef CONFIG_NO_HZ
+ /*
+ * Check if the do_timer duty was dropped. We don't care about
+ * concurrency: This happens only when the cpu in charge went
+ * into a long sleep. If two cpus happen to assign themself to
+ * this duty, then the jiffies update is still serialized by
+ * xtime_lock.
+ */
+ if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
+ tick_do_timer_cpu = cpu;
+#endif
+}
+
+#endif /* CONFIG_CPUSETS_NO_HZ */
+
/*
* High resolution timer specific code
*/
@@ -805,17 +845,7 @@ static enum hrtimer_restart tick_sched_timer(struct
hrtimer *timer)
ktime_t now = ktime_get();
int cpu = smp_processor_id();
-#ifdef CONFIG_NO_HZ
- /*
- * Check if the do_timer duty was dropped. We don't care about
- * concurrency: This happens only when the cpu in charge went
- * into a long sleep. If two cpus happen to assign themself to
- * this duty, then the jiffies update is still serialized by
- * xtime_lock.
- */
- if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
- tick_do_timer_cpu = cpu;
-#endif
+ tick_do_timer_check_handler(cpu);
/* Check, if the jiffies need an update */
if (tick_do_timer_cpu == cpu)
--
1.7.10.4
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