[PATCH 18/27] sched: Update nohz rq clock before searching busiest group on load balancing
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
Cc: Alessio Igor Bogani
Cc: Andrew Morton
Cc: Chris Metcalf
Cc: Christoph Lameter
Cc: Geoff Levand
Cc: Gilad Ben Yossef
Cc: Hakan Akkan
Cc: Ingo Molnar
Cc: Paul E. McKenney
Cc: Paul Gortmaker
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: Thomas Gleixner
---
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(_rq->lock);
+ update_rq_clock(this_rq);
+ raw_spin_unlock(_rq->lock);
+ local_irq_restore(flags);
+ }
+
redo:
group = find_busiest_group(, balance);
--
1.7.5.4
--
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[PATCH 18/27] sched: Update nohz rq clock before searching busiest group on load balancing
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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Please read the FAQ at http://www.tux.org/lkml/
