Messages in this thread Patch in this message | | | Subject | Re: sysbench+mysql(oltp, readonly) 30% regression with 2.6.26-rc1 | From | Peter Zijlstra <> | Date | Wed, 07 May 2008 18:26:15 +0200 |
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On Wed, 2008-05-07 at 12:55 +0800, Zhang, Yanmin wrote: > Comparing with kernel 2.6.25, sysbench+mysql(oltp, readonly) has many > regression with 2.6.26-rc1. > > 1) 8-core stoakley: 28%; > 2) 16-core tigerton: 20%; > 3) Itanium Montvale: 50%. > > Bisect located below patch. > > 8f1bc385cfbab474db6c27b5af1e439614f3025c is first bad commit > commit 8f1bc385cfbab474db6c27b5af1e439614f3025c > Author: Peter Zijlstra <a.p.zijlstra@chello.nl> > Date: Sat Apr 19 19:45:00 2008 +0200 > > sched: fair: weight calculations > > In order to level the hierarchy, we need to calculate load based on the > root view. That is, each task's load is in the same unit. > > > > After I manually reverted the patch against 2.6.26-rc1 while fixing a couple of > conflictions/errors, sysbench oltp regression became less than 3% on 8-core > stoakley.
Does this patch help?
--- From: Mike Galbraith <efault@gmx.de> 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
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- kernel/sched_fair.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
Index: linux-2.6-2/kernel/sched_fair.c =================================================================== --- linux-2.6-2.orig/kernel/sched_fair.c +++ linux-2.6-2/kernel/sched_fair.c @@ -662,10 +662,15 @@ place_entity(struct cfs_rq *cfs_rq, stru 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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