Messages in this thread | | | Date | Fri, 24 Jul 2009 10:00:01 +0530 | From | Bharata B Rao <> | Subject | Re: CFS group scheduler fairness broken starting from 2.6.29-rc1 |
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On Thu, Jul 23, 2009 at 03:17:18PM -0700, Ken Chen wrote: > On Thu, Jul 23, 2009 at 12:57 AM, Bharata B > Rao<bharata@linux.vnet.ibm.com> wrote: > > Hi, > > > > Group scheduler fainess is broken since 2.6.29-rc1. git bisect led me > > to this commit: > > > > commit ec4e0e2fe018992d980910db901637c814575914 > > Author: Ken Chen <kenchen@google.com> > > Date: Tue Nov 18 22:41:57 2008 -0800 > > > > sched: fix inconsistency when redistribute per-cpu tg->cfs_rq shares > > > > Impact: make load-balancing more consistent > > .... > > > > ====================================================================== > > % CPU time division b/n groups > > Group 2.6.29-rc1 2.6.29-rc1 w/o the above patch > > ====================================================================== > > a with 8 tasks 44 31 > > b with 5 tasks 32 34 > > c with 3 tasks 22 34 > > ====================================================================== > > All groups had equal shares. > > What value did you use for each task_group's share? For very large > value of tg->shares, it could be that all of the boost went to one CPU > and subsequently causes load-balancer to shuffle tasks around. Do you > see any unexpected task migration?
Used default 1024 for each group.
Without your patch, each of the tasks see around 165 migrations during a 60s run, but with your patch, they see 125 migrations (as per se.nr_migrations). I am using a 8CPU machine here.
Regards, Bharata. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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