5.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Vincent Guittot vincent.guittot@linaro.org
[ 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@linaro.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Ingo Molnar mingo@kernel.org Reviewed-by: Valentin Schneider valentin.schneider@arm.com Link: https://lkml.kernel.org/r/20210224133007.28644-5-vincent.guittot@linaro.org Stable-dep-of: ff47a0acfcce ("sched/fair: Check idle_cpu() before need_resched() to detect ilb CPU turning busy") Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/fair.c | 32 +++++++------------------------- 1 file changed, 7 insertions(+), 25 deletions(-)
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));