From f07333bf6ee66d9b49286cec4371cf375e745b7a Mon Sep 17 00:00:00 2001 From: Paul Turner Date: Fri, 21 Jan 2011 20:45:03 -0800 Subject: sched: Avoid expensive initial update_cfs_load() Since cfs->{load_stamp,load_last} are zero-initalized the initial load update will consider the delta to be 'since the beginning of time'. This results in a lot of pointless divisions to bring this large period to be within the sysctl_sched_shares_window. Fix this by initializing load_stamp to be 1 at cfs_rq initialization, this allows for an initial load_stamp > load_last which then lets standard idle truncation proceed. We avoid spinning (and slightly improve consistency) by fixing delta to be [period - 1] in this path resulting in a slightly more predictable shares ramp. (Previously the amount of idle time preserved by the overflow would range between [period/2,period-1].) Signed-off-by: Paul Turner Signed-off-by: Peter Zijlstra LKML-Reference: <20110122044852.102126037@google.com> Signed-off-by: Ingo Molnar --- kernel/sched_fair.c | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel/sched_fair.c') diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 0c550c841ee..4cbc9121094 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -733,6 +733,7 @@ static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update) now - cfs_rq->load_last > 4 * period) { cfs_rq->load_period = 0; cfs_rq->load_avg = 0; + delta = period - 1; } cfs_rq->load_stamp = now; -- cgit v1.2.3-70-g09d2