sched/fair: fix use stale overloaded status to find busiest group
PATCH 1/1 sched/fair: fix use stale overloaded status to find busiest group
Commit caeb178c60f4 ("sched/fair: Make update_sd_pick_busiest() return 'true' on a busier sd") makes groups are ranked in the order overloaded > imbalance > other and busiest group is picked according to this order. sgs->group_capacity_factor is used to check if group is overloaded. In the case of the child domain prefers tasks go to siblings first, the sgs->group_capacity_factor will be set lower to one in order to move all the excess tasks away. However, group overloaded status is not updated in the case of sgs->group_capacity_factor be set lower to one which leads to miss find the busiest group. This patch fix it by updating group overloaded status in the case of sg capacity factor is set to one in order to find busiest group accurately.
--- kernel/sched/fair.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
kernel/sched/fair.c +3 -1
@@ -6344,8 +6344,10 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd* with a large weight task outweighs the tasks on the system). */ if (prefer_sibling && sds->local && - sds->local_stat.group_has_free_capacity) + sds->local_stat.group_has_free_capacity) { sgs->group_capacity_factor =min (sgs->group_capacity_factor,1U ); + sgs->group_type =group_classify (sg, sgs); + }if (update_sd_pick_busiest (env, sds, sg, sgs)) { sds->busiest = sg;
Signature · 1 line
1.9.1
Peter Zijlstra
maintainerQuoted 11 lines · Wanpeng Li
Commit
caeb178c60f4("sched/fair: Makeupdate_sd_pick_busiest()return 'true' on a busier sd") makes groups are ranked in the order overloaded > imbalance > other and busiest group is picked according to this order.sgs->group_capacity_factoris used to check if group is overloaded. In the case of the child domain prefers tasks go to siblings first, thesgs->group_capacity_factorwill be set lower to one in order to move all the excess tasks away. However, group overloaded status is not updated in the case ofsgs->group_capacity_factorbe set lower to one which leads to miss find the busiest group. This patch fix it by updating group overloaded status in the case of sg capacity factor is set to one in order to find busiest group accurately.
You noticed this while going over Vincents patches, right?
Also, try and introduce some newlines in the changelog, paragraphs of 3-5 lines are best.
Hi Peter,
Quoted 12 lines · Peter Zijlstra
Quoted 11 lines · Wanpeng Li
Commit
caeb178c60f4("sched/fair: Makeupdate_sd_pick_busiest()return 'true' on a busier sd") makes groups are ranked in the order overloaded > imbalance > other and busiest group is picked according to this order.sgs->group_capacity_factoris used to check if group is overloaded. In the case of the child domain prefers tasks go to siblings first, thesgs->group_capacity_factorwill be set lower to one in order to move all the excess tasks away. However, group overloaded status is not updated in the case ofsgs->group_capacity_factorbe set lower to one which leads to miss find the busiest group. This patch fix it by updating group overloaded status in the case of sg capacity factor is set to one in order to find busiest group accurately.
Quoted 1 line
You noticed this while going over Vincents patches, right?
Indeed. ;-)
Quoted 3 lines
Also, try and introduce some newlines in the changelog, paragraphs of 3-5 lines are best.
Ok, I will send a new version tomorrow. ;-)
Regards,
Wanpeng Li
Quoted 5 lines
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