This is a note to let you know that I've just added the patch titled
sched/fair: Merge for each idle cpu loop of ILB
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-fair-merge-for-each-idle-cpu-loop-of-ilb.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 2c353fb77d9fe2fbdb486d7ae22236f70374e129
Author: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Date: Wed Feb 24 14:30:04 2021 +0100
sched/fair: Merge for each idle cpu loop of ILB
[ Upstream commit 7a82e5f52a3506bc35a4dc04d53ad2c9daf82e7f ]
Remove the specific case for handling this_cpu outside for_each_cpu() loop
when running ILB. Instead we use for_each_cpu_wrap() and start with the
next cpu after this_cpu so we will continue to finish with this_cpu.
update_nohz_stats() is now used for this_cpu too and will prevents
unnecessary update. We don't need a special case for handling the update of
nohz.next_balance for this_cpu anymore because it is now handled by the
loop like others.
Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Valentin Schneider <valentin.schneider@xxxxxxx>
Link: https://lkml.kernel.org/r/20210224133007.28644-5-vincent.guittot@xxxxxxxxxx
Stable-dep-of: ff47a0acfcce ("sched/fair: Check idle_cpu() before need_resched() to detect ilb CPU turning busy")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 0af373c4d7450..ab29666eb50ed 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10333,22 +10333,9 @@ static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
* When the cpu is attached to null domain for ex, it will not be
* updated.
*/
- if (likely(update_next_balance)) {
+ if (likely(update_next_balance))
rq->next_balance = next_balance;
-#ifdef CONFIG_NO_HZ_COMMON
- /*
- * If this CPU has been elected to perform the nohz idle
- * balance. Other idle CPUs have already rebalanced with
- * nohz_idle_balance() and nohz.next_balance has been
- * updated accordingly. This CPU is now running the idle load
- * balance for itself and we need to update the
- * nohz.next_balance accordingly.
- */
- if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
- nohz.next_balance = rq->next_balance;
-#endif
- }
}
static inline int on_null_domain(struct rq *rq)
@@ -10674,8 +10661,12 @@ static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
*/
smp_mb();
- for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
- if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
+ /*
+ * Start with the next CPU after this_cpu so we will end with this_cpu and let a
+ * chance for other idle cpu to pull load.
+ */
+ for_each_cpu_wrap(balance_cpu, nohz.idle_cpus_mask, this_cpu+1) {
+ if (!idle_cpu(balance_cpu))
continue;
/*
@@ -10721,15 +10712,6 @@ static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
if (likely(update_next_balance))
nohz.next_balance = next_balance;
- /* Newly idle CPU doesn't need an update */
- if (idle != CPU_NEWLY_IDLE) {
- update_blocked_averages(this_cpu);
- has_blocked_load |= this_rq->has_blocked_load;
- }
-
- if (flags & NOHZ_BALANCE_KICK)
- rebalance_domains(this_rq, CPU_IDLE);
-
WRITE_ONCE(nohz.next_blocked,
now + msecs_to_jiffies(LOAD_AVG_PERIOD));
