Messages in this thread | | | Date | Tue, 29 Jul 2014 16:59:10 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/2] sched: fix and clean up calculate_imbalance |
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On Tue, Jul 29, 2014 at 11:04:50AM +0200, Vincent Guittot wrote: > > In situations where all the domains are overloaded, or where only the > > busiest domain is overloaded, that code is also superfluous, since > > the normal env->imbalance calculation will figure out how much to move. > > Remove the load_above_capacity calculation. > > IMHO, we should not remove that part which is used by prefer_sibling > > Originally, we had 2 type of busiest group: overloaded or imbalanced. > You add a new one which has only a avg_load higher than other so you > should handle this new case and keep the other ones unchanged
Right, so we want that code for overloaded -> overloaded migrations such as not to cause idle cpus in an attempt to balance things. Idle cpus are worse than imbalance.
But in case of overloaded/imb -> !overloaded migrations we can allow it, and in fact want to allow it in order to balance idle cpus.
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