* Vincent Guittot <vincent.guit...@linaro.org> [2015-02-27 16:54:13]:
> Add the SD_PREFER_SIBLING flag for SMT level in order to ensure that
> the scheduler will put at least 1 task per core.
>
> Signed-off-by: Vincent Guittot <vincent.guit...@linaro.org>
> Reviewed-by: Preeti U. Murthy <pre...@linux.vnet.ibm.com>
> ---
> kernel/sched/core.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 29f7037..753f0a2 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6240,6 +6240,7 @@ sd_init(struct sched_domain_topology_level *tl, int cpu)
> */
>
> if (sd->flags & SD_SHARE_CPUCAPACITY) {
> + sd->flags |= SD_PREFER_SIBLING;
> sd->imbalance_pct = 110;
> sd->smt_gain = 1178; /* ~15% */
>
Prefer siblings logic dates back to https://lkml.org/lkml/2009/8/27/210
and only used in update_sd_lb_stats() where we have
if (child && child->flags & SD_PREFER_SIBLING)
prefer_sibling = 1;
However what confuses me is why should we even look at a child domain's
flag to balance tasks across the current sched domain? Why cant we just
set and use a sd flag at current level than to look at child domain
flag?
> --
> 1.9.1
>
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--
Thanks and Regards
Srikar Dronamraju
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