Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH 08/41] nohz: Try not to give the timekeeping duty to an adaptive tickless cpu | Date | Tue, 1 May 2012 01:54:42 +0200 |
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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 <fweisbec@gmail.com> Cc: Alessio Igor Bogani <abogani@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Avi Kivity <avi@redhat.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@ti.com> Cc: Max Krasnyansky <maxk@qualcomm.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephen Hemminger <shemminger@vyatta.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> --- kernel/time/tick-sched.c | 52 ++++++++++++++++++++++++++++++++++++--------- 1 files changed, 41 insertions(+), 11 deletions(-)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 0695e9d..f1142d5 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> @@ -782,6 +783,45 @@ 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 */ @@ -798,17 +838,7 @@ 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) -- 1.7.5.4
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