On Wed, Feb 19, 2014 at 01:20:30PM +0800, Lei Wen wrote:
> Since cpu which is put into quiescent mode, would remove itself
> from kernel's sched_domain. So we could use search sched_domain
> method to check whether this cpu don't want to be disturbed as
> idle load balance would send IPI to it.
>
> Signed-off-by: Lei Wen <lei...@marvell.com>
> ---
> kernel/sched/fair.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 235cfa7..14230ae 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6783,6 +6783,8 @@ out_unlock:
> * - When one of the busy CPUs notice that there may be an idle rebalancing
> * needed, they will kick the idle load balancer, which then does idle
> * load balancing for all the idle CPUs.
> + * - exclude those cpus not inside current call_cpu's sched_domain, so that
> + * those isolated cpu could be kept in their quisecnt mode.
> */
> static struct {
> cpumask_var_t idle_cpus_mask;
> @@ -6792,10 +6794,16 @@ static struct {
>
> static inline int find_new_ilb(void)
> {
> - int ilb = cpumask_first(nohz.idle_cpus_mask);
> + int ilb;
> + int cpu = smp_processor_id();
> + struct sched_domain *tmp;
>
> - if (ilb < nr_cpu_ids && idle_cpu(ilb))
> - return ilb;
> + for_each_domain(cpu, tmp) {
> + ilb = cpumask_first_and(nohz.idle_cpus_mask,
> + sched_domain_span(tmp));
> + if (ilb < nr_cpu_ids && idle_cpu(ilb))
> + return ilb;
> + }
The ILB code is bad; but you just made it horrible. Don't add pointless
for_each_domain() iterations.
I'm thinking something like:
ilb = cpumask_first_and(nohz.idle_cpus_mask, this_rq()->rd.span);
Should work just fine, no?
Better still would be to maybe not participate in the ILB in the first
place and leave this selection loop alone.
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