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Date: Mon, 4 Apr 2016 15:23:21 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>, James Hartsock <hartsjc@redhat.com>,
        Rik van Riel <riel@redhat.com>,
        Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
        Kirill Tkhai <ktkhai@parallels.com>, linux-kernel@vger.kernel.org
Subject: Re: [RFC] sched: unused cpu in affine workload
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On Mon, Apr 04, 2016 at 11:38:44AM +0200, Ingo Molnar wrote:
> We'd upgrade that to O(nr_cpus^2), which is totally unrealistic with 16,000 CPUs 
> even in a slowpath - but it would probably cause problems even with 120 CPUs. It 
> will get quadratically worse as the number of CPUs in a system increases on its 
> current exponential trajectory ...

The arbitrary affinity thing is I think a packing problem, which is NP
hard IIRC.