From 46151122e0a2e80e5a6b2889f595e371fe2b600d Mon Sep 17 00:00:00 2001
From: Mike Galbraith <efault@gmx.de>
Date: Thu, 8 May 2008 17:00:42 +0200
Subject: 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>
---
kernel/sched_fair.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
(limited to 'kernel/sched_fair.c')
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index c863663d204d..e24ecd39c4b8 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. */
--
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