sched: Reduce contention in update_cfs_rq_blocked_load()

When running workloads on 2+ socket systems, based on perf profiles, the
update_cfs_rq_blocked_load() function often shows up as taking up a
noticeable % of run time.

Much of the contention is in __update_cfs_rq_tg_load_contrib() when we
update the tg load contribution stats.  However, it turns out that in many
cases, they don't need to be updated and "tg_contrib" is 0.

This patch adds a check in __update_cfs_rq_tg_load_contrib() to skip updating
tg load contribution stats when nothing needs to be updated. This reduces the
cacheline contention that would be unnecessary.

Reviewed-by: Ben Segall <>
Reviewed-by: Waiman Long <>
Signed-off-by: Jason Low <>
Signed-off-by: Peter Zijlstra <>
Cc: Paul Turner <>
Cc: Yuyang Du <>
Cc: Aswin Chandramouleeswaran <>
Cc: Chegu Vinod <>
Cc: Scott J Norton <>
Cc: Tim Chen <>
Cc: Linus Torvalds <>
Signed-off-by: Ingo Molnar <>
1 file changed