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authorFrederic Weisbecker <frederic@kernel.org>2018-02-21 05:17:27 +0100
committerIngo Molnar <mingo@kernel.org>2018-02-21 09:49:09 +0100
commitd84b31313ef8a8de55a2cbfb72f76f36d8c927fb (patch)
tree24101d3e47de3fbdadd962a02d816d6a2f5ceb12 /kernel/sched/rt.c
parent1bda3f8087fce9063da0b8aef87f17a3fe541aca (diff)
downloadlinux-d84b31313ef8a8de55a2cbfb72f76f36d8c927fb.tar.bz2
sched/isolation: Offload residual 1Hz scheduler tick
When a CPU runs in full dynticks mode, a 1Hz tick remains in order to keep the scheduler stats alive. However this residual tick is a burden for bare metal tasks that can't stand any interruption at all, or want to minimize them. The usual boot parameters "nohz_full=" or "isolcpus=nohz" will now outsource these scheduler ticks to the global workqueue so that a housekeeping CPU handles those remotely. The sched_class::task_tick() implementations have been audited and look safe to be called remotely as the target runqueue and its current task are passed in parameter and don't seem to be accessed locally. Note that in the case of using isolcpus, it's still up to the user to affine the global workqueues to the housekeeping CPUs through /sys/devices/virtual/workqueue/cpumask or domains isolation "isolcpus=nohz,domain". Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Christoph Lameter <cl@linux.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Rik van Riel <riel@redhat.com> Cc: Wanpeng Li <kernellwp@gmail.com> Link: http://lkml.kernel.org/r/1519186649-3242-6-git-send-email-frederic@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched/rt.c')
-rw-r--r--kernel/sched/rt.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index aad49451584e..c80563b4f6b9 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2292,6 +2292,14 @@ static void watchdog(struct rq *rq, struct task_struct *p)
static inline void watchdog(struct rq *rq, struct task_struct *p) { }
#endif
+/*
+ * scheduler tick hitting a task of our scheduling class.
+ *
+ * NOTE: This function can be called remotely by the tick offload that
+ * goes along full dynticks. Therefore no local assumption can be made
+ * and everything must be accessed through the @rq and @curr passed in
+ * parameters.
+ */
static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
{
struct sched_rt_entity *rt_se = &p->rt;