CPUSets have cpusets.quiesce sysfs file now, with which some CPUs can opt for isolating themselves from background kernel activities, like: timers & hrtimers.
get_nohz_timer_target() is used for finding suitable CPU for firing a timer. To guarantee that new timers wouldn't be queued on quiesced CPUs, we need to modify this routine.
Signed-off-by: Viresh Kumar viresh.kumar@linaro.org --- kernel/sched/core.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index c0339e2..b235af2 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -557,17 +557,18 @@ void resched_cpu(int cpu) */ int get_nohz_timer_target(int pinned) { - int cpu = smp_processor_id(); - int i; + int cpu = smp_processor_id(), i; struct sched_domain *sd;
- if (pinned || !get_sysctl_timer_migration() || !idle_cpu(cpu)) + if (pinned || !get_sysctl_timer_migration() || + !(idle_cpu(cpu) || cpu_quiesced(cpu))) return cpu;
rcu_read_lock(); for_each_domain(cpu, sd) { for_each_cpu(i, sched_domain_span(sd)) { - if (!idle_cpu(i)) { + /* Don't push timers to quiesced CPUs */ + if (!(cpu_quiesced(i) || idle_cpu(i))) { cpu = i; goto unlock; }