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Date: Mon, 11 Nov 2013 11:26:37 -0800
From: Arjan van de Ven <arjan@linux.intel.com>
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To: Catalin Marinas <catalin.marinas@arm.com>,
        Morten Rasmussen <morten.rasmussen@arm.com>
CC: Vincent Guittot <vincent.guittot@linaro.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>,
        Paul Turner <pjt@google.com>, Chris Metcalf <cmetcalf@tilera.com>,
        Tony Luck <tony.luck@intel.com>,
        "alex.shi@intel.com" <alex.shi@intel.com>,
        Preeti U Murthy <preeti@linux.vnet.ibm.com>,
        linaro-kernel <linaro-kernel@lists.linaro.org>,
        "len.brown@intel.com" <len.brown@intel.com>,
        "l.majewski@samsung.com" <l.majewski@samsung.com>,
        Jonathan Corbet <corbet@lwn.net>, "Rafael J. Wysocki" <rjw@sisk.pl>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>
Subject: Re: [RFC][PATCH v5 00/14] sched: packing tasks
References: <1382097147-30088-1-git-send-email-vincent.guittot@linaro.org> <CAHkRjk69GNYtLGBSWCNcsCzkBHywKrD0qQQbNkJRpMbcdsCPyw@mail.gmail.com> <20131111165453.GB4586@e103034-lin> <20131111183142.GF29572@arm.com>
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On 11/11/2013 10:31 AM, Catalin Marinas wrote:
> I agree, we can't rely on the requested C-state but the_actual_  state
> and this means querying the hardware driver. Can we abstract this via
> some interface which provides the cost of waking up a CPU? This could
> take into account the state of the other CPUs in the cluster and the
> scheduler is simply concerned with the wake-up costs.

can you even query this without actually waking up the cpu and asking ???