Commit-ID: 8236d907ab3411ad452280faa8b26c1347327380 Gitweb: http://git.kernel.org/tip/8236d907ab3411ad452280faa8b26c1347327380 Author: Jason Low <[email protected]> AuthorDate: Tue, 2 Sep 2014 00:41:24 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Tue, 9 Sep 2014 06:47:29 +0200
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]> --- kernel/sched/fair.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 50d2025..be9e97b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2382,6 +2382,9 @@ static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq, tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg; tg_contrib -= cfs_rq->tg_load_contrib; + if (!tg_contrib) + return; + if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) { atomic_long_add(tg_contrib, &tg->load_avg); cfs_rq->tg_load_contrib += tg_contrib; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
