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 <[email protected]>
Reviewed-by: Waiman Long <[email protected]>
Signed-off-by: Jason Low <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Paul Turner <[email protected]>
Cc: [email protected]
Cc: Yuyang Du <[email protected]>
Cc: Aswin Chandramouleeswaran <[email protected]>
Cc: Chegu Vinod <[email protected]>
Cc: Scott J Norton <[email protected]>
Cc: Tim Chen <[email protected]>
Cc: Linus Torvalds <[email protected]>
Link: http://lkml.kernel.org/r/1409643684.19197.15.camel@j-VirtualBox
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions