On Wed, 2016-03-23 at 17:04 +0530, Srikar Dronamraju wrote: > If asymmetric packing is used when target cpu is busy, > update_sd_pick_busiest(), can select a lightly loaded cpu. > find_busiest_group() has checks to ensure asym packing is only used > when target cpu is not busy. However it may not be able to avoid a > lightly loaded cpu selected by update_sd_pick_busiest from being > selected as source cpu for eventual load balancing. > > Also when using asymmetric scheduling, always select higher cpu as > source cpu for load balancing. > > While doing this change, move the check to see if target cpu is busy > into check_asym_packing(). > > 1. Record per second ebizzy (32 threads) on a 64 cpu power 7 box. (5 > iterations) > 4.5.0-master/ebizzy_32.out > N Min Max Median Avg Stddev > x 5 5205896 17260530 12141204 10759008 4765419 > > 4.5.0-master-asym-changes/ebizzy_32.out > N Min Max Median Avg Stddev > x 5 7044349 19112876 17440718 14947658 5263970 > > 2. Record per second ebizzy (32 threads) on a 64 cpu power 7 box. (5 > iterations) > 4.5.0-master/ebizzy_64.out > N Min Max Median Avg Stddev > x 5 5400083 14091418 8673907 8872662.4 3389746.8 > > 4.5.0-master-asym-changes/ebizzy_64.out > N Min Max Median Avg Stddev > x 5 7533907 17232623 15083583 13364894 3776877.9 > > 3. Record per second ebizzy (32 threads) on a 64 cpu power 7 box. (5 > iterations) > 4.5.0-master/ebizzy_128.out > N Min Max Median Avg Stddev > x 5 35328039 41642699 37564951 38378409 2671280 > > 4.5.0-master-asym-changes/ebizzy_128.out > N Min Max Median Avg Stddev > x 5 37102220 42736809 38442478 39529626 2298389.4
I'm not sure how to interpret these. Any chance you can give a summary of what these results mean? > Signed-off-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com> FWIW, this still passes my scheduler tests on POWER7, but they weren't failing before anyway. Mikey > --- > kernel/sched/fair.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 56b7d4b..9abfb16 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6517,6 +6517,8 @@ static bool update_sd_pick_busiest(struct lb_env *env, > if (!(env->sd->flags & SD_ASYM_PACKING)) > return true; > > + if (env->idle == CPU_NOT_IDLE) > + return true; > /* > * ASYM_PACKING needs to move all the work to the lowest > * numbered CPUs in the group, therefore mark all groups > @@ -6526,7 +6528,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, > if (!sds->busiest) > return true; > > - if (group_first_cpu(sds->busiest) > group_first_cpu(sg)) > + if (group_first_cpu(sds->busiest) < group_first_cpu(sg)) > return true; > } > > @@ -6672,6 +6674,9 @@ static int check_asym_packing(struct lb_env *env, > struct sd_lb_stats *sds) > if (!(env->sd->flags & SD_ASYM_PACKING)) > return 0; > > + if (env->idle == CPU_NOT_IDLE) > + return 0; > + > if (!sds->busiest) > return 0; > > @@ -6864,8 +6869,7 @@ static struct sched_group *find_busiest_group(struct > lb_env *env) > busiest = &sds.busiest_stat; > > /* ASYM feature bypasses nice load balance check */ > - if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) && > - check_asym_packing(env, &sds)) > + if (check_asym_packing(env, &sds)) > return sds.busiest; > > /* There is no busy sibling group to pull tasks from */
