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" <yanmin_zhang@linux.intel.com> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -662,10 +662,15 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
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if (!initial) {
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/* sleeps upto a single latency don't count. */
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if (sched_feat(NEW_FAIR_SLEEPERS)) {
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unsigned long thresh = sysctl_sched_latency;
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/*
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* convert the sleeper threshold into virtual time
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*/
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if (sched_feat(NORMALIZED_SLEEPER))
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vruntime -= calc_delta_weight(sysctl_sched_latency, se);
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else
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vruntime -= sysctl_sched_latency;
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thresh = calc_delta_fair(thresh, se);
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vruntime -= thresh;
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}
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/* ensure we never gain time by being placed backwards. */
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