While load balancing an rq target, we look for the busiest group.
This operation may require an uptodate rq clock if we end up calling
scale_rt_power(). To this end, update it manually if the target is
running tickless.
DOUBT: don't we actually also need this in vanilla kernel, in case
this_cpu is in dyntick-idle mode?
Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
Cc: Alessio Igor Bogani <abog...@kernel.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Chris Metcalf <cmetc...@tilera.com>
Cc: Christoph Lameter <c...@linux.com>
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: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortma...@windriver.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Thomas Gleixner <t...@linutronix.de>
---
kernel/sched/fair.c | 13 +++++++++++++
1 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 698137d..473f50f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5023,6 +5023,19 @@ static int load_balance(int this_cpu, struct rq *this_rq,
schedstat_inc(sd, lb_count[idle]);
+ /*
+ * find_busiest_group() may need an uptodate cpu clock
+ * for find_busiest_group() (see scale_rt_power()). If
+ * the CPU is nohz, it's clock may be stale.
+ */
+ if (tick_nohz_full_cpu(this_cpu)) {
+ local_irq_save(flags);
+ raw_spin_lock(&this_rq->lock);
+ update_rq_clock(this_rq);
+ raw_spin_unlock(&this_rq->lock);
+ local_irq_restore(flags);
+ }
+
redo:
group = find_busiest_group(&env, balance);
--
1.7.5.4
--
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