On Mon, Aug 19, 2013 at 9:01 AM, Peter Zijlstra <pet...@infradead.org> wrote: > I found that on my wsm box I had a redundant domain: > > [ 0.949769] CPU0 attaching sched-domain: > [ 0.953765] domain 0: span 0,12 level SIBLING > [ 0.958335] groups: 0 (cpu_power = 587) 12 (cpu_power = 588) > [ 0.964548] domain 1: span 0-5,12-17 level MC > [ 0.969206] groups: 0,12 (cpu_power = 1175) 1,13 (cpu_power = 1176) > 2,14 (cpu_power = 1176) 3,15 (cpu_power = 1176) 4,16 (cpu_power = 1176) 5,17 > (cpu_power = 1176) > [ 0.984993] domain 2: span 0-5,12-17 level CPU > [ 0.989822] groups: 0-5,12-17 (cpu_power = 7055) > [ 0.995049] domain 3: span 0-23 level NUMA > [ 0.999620] groups: 0-5,12-17 (cpu_power = 7055) 6-11,18-23 > (cpu_power = 7056) > > Note how domain 2 has only a single group and spans the same CPUs as > domain 1. We should not keep such domains and do in fact have code to > prune these. > > It turns out that the 'new' SD_PREFER_SIBLING flag causes this, it > makes sd_parent_degenerate() fail on the CPU domain. We can easily fix > this by 'ignoring' the SD_PREFER_SIBLING bit and transfering it to > whatever domain ends up covering the span. > > With this patch the domains now look like this: > > [ 0.950419] CPU0 attaching sched-domain: > [ 0.954454] domain 0: span 0,12 level SIBLING > [ 0.959039] groups: 0 (cpu_power = 587) 12 (cpu_power = 588) > [ 0.965271] domain 1: span 0-5,12-17 level MC > [ 0.969936] groups: 0,12 (cpu_power = 1175) 1,13 (cpu_power = 1176) > 2,14 (cpu_power = 1176) 3,15 (cpu_power = 1176) 4,16 (cpu_power = 1176) 5,17 > (cpu_power = 1176) > [ 0.985737] domain 2: span 0-23 level NUMA > [ 0.990231] groups: 0-5,12-17 (cpu_power = 7055) 6-11,18-23 (cpu_power > = 7056) > > Signed-off-by: Peter Zijlstra <pet...@infradead.org> > --- > kernel/sched/core.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -4948,7 +4948,8 @@ sd_parent_degenerate(struct sched_domain > SD_BALANCE_FORK | > SD_BALANCE_EXEC | > SD_SHARE_CPUPOWER | > - SD_SHARE_PKG_RESOURCES); > + SD_SHARE_PKG_RESOURCES | > + SD_PREFER_SIBLING); > if (nr_node_ids == 1) > pflags &= ~SD_SERIALIZE; > } > @@ -5157,6 +5158,13 @@ cpu_attach_domain(struct sched_domain *s > tmp->parent = parent->parent; > if (parent->parent) > parent->parent->child = tmp; > + /* > + * Transfer SD_PREFER_SIBLING down in case of a > + * degenerate parent; the spans match for this > + * so the property transfers. > + */ > + if (parent->flags & SD_PREFER_SIBLING) > + tmp->flags |= SD_PREFER_SIBLING; > destroy_sched_domain(parent, cpu); > } else > tmp = tmp->parent; >
Reviewed-by: Paul Turner <p...@google.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
