Messages in this thread Patch in this message | | | From | Wanpeng Li <> | Subject | [PATCH] sched/fair: Fix the nohz.next_balance update mess | Date | Sun, 5 Feb 2017 01:57:35 -0800 |
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From: Wanpeng Li <wanpeng.li@hotmail.com>
The commit: c5afb6a87f2 ("sched/fair: Fix nohz.next_balance update")
intends to update nohz.next_balance in two steps.
1) The ILB CPU utilizes next_balance variable in nohz_idle_balance() to gather the shortest next balance of other idle CPUs before updating nohz.next_balance. 2) The ILB CPU updates the nohz.next_balance according to its own next_balance after load balance on behalf of other idle CPUs.
However, there is a mess which breaks the original intention of the first step, every idle CPUs update nohz.next_balance during ILB CPU on behalf of them to do load balance, and then the ILB CPU utilizes next_balance variable in nohz_idle_balance() to gather the shortest next balance of other idle CPUs before updating nohz.next_balance.
This patch fixes it by don't update nohz.next_balance for other idle CPUs when ILB CPU on behalf of them to do load balance.
Cc: Vincent Guittot <vincent.guittot@linaro.org> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> CC: Ingo Molnar <mingo@kernel.org> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> --- kernel/sched/fair.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 274c747..83948a4 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8750,7 +8750,8 @@ static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle) * 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)) + if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance) && + !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_rq()->cpu))) nohz.next_balance = rq->next_balance; #endif } -- 2.7.4
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