From 46151122e0a2e80e5a6b2889f595e371fe2b600d Mon Sep 17 00:00:00 2001 From: Mike Galbraith Date: Thu, 8 May 2008 17:00:42 +0200 Subject: [PATCH] sched: fix weight calculations The conversion between virtual and real time is as follows: dvt = rw/w * dt <=> dt = w/rw * dvt Since we want the fair sleeper granularity to be in real time, we actually need to do: dvt = - rw/w * l This bug could be related to the regression reported by Yanmin Zhang: | Comparing with kernel 2.6.25, sysbench+mysql(oltp, readonly) has lots | of regressions with 2.6.26-rc1: | | 1) 8-core stoakley: 28%; | 2) 16-core tigerton: 20%; | 3) Itanium Montvale: 50%. Reported-by: "Zhang, Yanmin" Signed-off-by: Mike Galbraith Signed-off-by: Peter Zijlstra Signed-off-by: Ingo Molnar --- kernel/sched_fair.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index c863663d204..e24ecd39c4b 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -662,10 +662,15 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) if (!initial) { /* sleeps upto a single latency don't count. */ if (sched_feat(NEW_FAIR_SLEEPERS)) { + unsigned long thresh = sysctl_sched_latency; + + /* + * convert the sleeper threshold into virtual time + */ if (sched_feat(NORMALIZED_SLEEPER)) - vruntime -= calc_delta_weight(sysctl_sched_latency, se); - else - vruntime -= sysctl_sched_latency; + thresh = calc_delta_fair(thresh, se); + + vruntime -= thresh; } /* ensure we never gain time by being placed backwards. */ -- 2.41.1