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SubjectRe: [PATCH 2/2] sched: trigger_load_balance clean up
On 09/12/2012 02:36 AM, Suresh Siddha wrote:

> On Mon, 2012-09-10 at 15:10 +0800, Alex Shi wrote:
>> Remove a redundant check for on_null_domain(cpu), and rerange the code
>> that make it more readable.
>
> hmm, but we are now doing the on_null_domain() check always,
> irrespective of whether we need the load balance or not.
>
> do we really need the on_null_domain() check there? What happens if we
> just remove it?


A very very simple try can not show removing causes crash. But as to
RCU details, I don't know. :(

CC to Paul

>
> thanks,
> suresh
>
>>
>> Signed-off-by: Alex Shi <alex.shi@intel.com>
>> ---
>> kernel/sched/fair.c | 8 +++++---
>> 1 files changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 5bbc4bf..529092d 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -4934,11 +4934,13 @@ static inline int on_null_domain(int cpu)
>> void trigger_load_balance(struct rq *rq, int cpu)
>> {
>> /* Don't need to rebalance while attached to NULL domain */
>> - if (time_after_eq(jiffies, rq->next_balance) &&
>> - likely(!on_null_domain(cpu)))
>> + if (unlikely(on_null_domain(cpu)))
>> + return;
>> +
>> + if (time_after_eq(jiffies, rq->next_balance))
>> raise_softirq(SCHED_SOFTIRQ);
>> #ifdef CONFIG_NO_HZ
>> - if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
>> + if (nohz_kick_needed(rq, cpu))
>> nohz_balancer_kick(cpu);
>> #endif
>> }
>
>




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