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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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