From 3f2aa307c4d26b4ed6509d0a79e8254c9e07e921 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Thu, 10 Sep 2009 20:34:48 +0200 Subject: [PATCH] sched: Disable NEW_FAIR_SLEEPERS for now Nikos Chantziaras and Jens Axboe reported that turning off NEW_FAIR_SLEEPERS improves desktop interactivity visibly. Nikos described his experiences the following way: " With this setting, I can do "nice -n 19 make -j20" and still have a very smooth desktop and watch a movie at the same time. Various other annoyances (like the "logout/shutdown/restart" dialog of KDE not appearing at all until the background fade-out effect has finished) are also gone. So this seems to be the single most important setting that vastly improves desktop behavior, at least here. " Jens described it the following way, referring to a 10-seconds xmodmap scheduling delay he was trying to debug: " Then I tried switching NO_NEW_FAIR_SLEEPERS on, and then I get: Performance counter stats for 'xmodmap .xmodmap-carl': 9.009137 task-clock-msecs # 0.447 CPUs 18 context-switches # 0.002 M/sec 1 CPU-migrations # 0.000 M/sec 315 page-faults # 0.035 M/sec 0.020167093 seconds time elapsed Woot! " So disable it for now. In perf trace output i can see weird delta timestamps: cc1-9943 [001] 2802.059479616: sched_stat_wait: task: as:9944 wait: 2801938766276 [ns] That nsec field is not supposed to be that large. More digging is needed - but lets turn it off while the real bug is found. Reported-by: Nikos Chantziaras Tested-by: Nikos Chantziaras Reported-by: Jens Axboe Tested-by: Jens Axboe Acked-by: Peter Zijlstra Cc: Mike Galbraith LKML-Reference: <4AA93D34.8040500@arcor.de> Signed-off-by: Ingo Molnar --- kernel/sched_features.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched_features.h b/kernel/sched_features.h index 4569bfa7df9b..e2dc63a5815d 100644 --- a/kernel/sched_features.h +++ b/kernel/sched_features.h @@ -1,4 +1,4 @@ -SCHED_FEAT(NEW_FAIR_SLEEPERS, 1) +SCHED_FEAT(NEW_FAIR_SLEEPERS, 0) SCHED_FEAT(NORMALIZED_SLEEPER, 0) SCHED_FEAT(ADAPTIVE_GRAN, 1) SCHED_FEAT(WAKEUP_PREEMPT, 1)