The following commit has been merged into the sched/core branch of tip:
Commit-ID: 5fd6d7f43958cb62da105c8413eac3e78480f09a
Gitweb: https://git.kernel.org/tip/5fd6d7f43958cb62da105c8413eac3e78480f09a
Author: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
AuthorDate: Thu, 06 Apr 2023 13:31:41 -07:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 08 May 2023 10:58:35 +02:00
sched/fair: Keep a fully_busy SMT sched group as busiest
When comparing two fully_busy scheduling groups, keep the current busiest
group if it represents an SMT core. Tasks in such scheduling group share
CPU resources and need more help than tasks in a non-SMT fully_busy group.
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: Zhang Rui <rui.zhang@xxxxxxxxx>
Link: https://lore.kernel.org/r/20230406203148.19182-6-ricardo.neri-calderon@xxxxxxxxxxxxxxx
---
kernel/sched/fair.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 85ce249..4a9f040 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9619,10 +9619,22 @@ static bool update_sd_pick_busiest(struct lb_env *env,
* contention when accessing shared HW resources.
*
* XXX for now avg_load is not computed and always 0 so we
- * select the 1st one.
+ * select the 1st one, except if @sg is composed of SMT
+ * siblings.
*/
- if (sgs->avg_load <= busiest->avg_load)
+
+ if (sgs->avg_load < busiest->avg_load)
return false;
+
+ if (sgs->avg_load == busiest->avg_load) {
+ /*
+ * SMT sched groups need more help than non-SMT groups.
+ * If @sg happens to also be SMT, either choice is good.
+ */
+ if (sds->busiest->flags & SD_SHARE_CPUCAPACITY)
+ return false;
+ }
+
break;
case group_has_spare:
|