From mboxrd@z Thu Jan 1 00:00:00 1970 From: Morten Rasmussen Subject: [RFC PATCH 01/16] sched: Documentation for scheduler energy cost model Date: Fri, 23 May 2014 19:16:28 +0100 Message-ID: <1400869003-27769-2-git-send-email-morten.rasmussen@arm.com> References: <1400869003-27769-1-git-send-email-morten.rasmussen@arm.com> Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Return-path: Received: from service87.mimecast.com ([91.220.42.44]:35914 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751257AbaEWSQu (ORCPT ); Fri, 23 May 2014 14:16:50 -0400 In-Reply-To: <1400869003-27769-1-git-send-email-morten.rasmussen@arm.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, peterz@infradead.org, mingo@kernel.org Cc: rjw@rjwysocki.net, vincent.guittot@linaro.org, daniel.lezcano@linaro.org, preeti@linux.vnet.ibm.com, dietmar.eggemann@arm.com This documentation patch provide a brief overview of the experimental scheduler energy costing model and associated data structures. Signed-off-by: Morten Rasmussen --- Documentation/scheduler/sched-energy.txt | 66 ++++++++++++++++++++++++++= ++++ 1 file changed, 66 insertions(+) create mode 100644 Documentation/scheduler/sched-energy.txt diff --git a/Documentation/scheduler/sched-energy.txt b/Documentation/sched= uler/sched-energy.txt new file mode 100644 index 0000000..c6896c0 --- /dev/null +++ b/Documentation/scheduler/sched-energy.txt @@ -0,0 +1,66 @@ +Energy cost model for energy-aware scheduling (EXPERIMENTAL) + +Introduction +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +The basic energy model uses platform energy data stored in sched_energy da= ta +structures attached to the sched_groups in the sched_domain hierarchy. The +energy cost model offers two function that can be used to guide scheduling +decisions: + +1.=09energy_diff_util(cpu, util, wakeups)=20 +2.=09energy_diff_task(cpu, task) + +Both return the energy cost delta caused by adding/removing utilization or= a +task to/from a specific cpu. + +CONFIG_SCHED_ENERGY needs to be defined in Kconfig to enable the energy co= st +model and associated data structures. + +The basic algorithm +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +The basic idea is to determine the energy cost at each level in sched_doma= in +hierarchy based on utilization: + +=09for_each_domain(cpu, sd) { +=09=09sg =3D sched_group_of(cpu) +=09=09energy_before =3D curr_util(sg) * busy_power(sg) + =09 + 1-curr_util(sg) * idle_power(sg) +=09=09energy_after =3D new_util(sg) * busy_power(sg) + =09 + 1-new_util(sg) * idle_power(sg) + =09+ new_util(sg) * task_wakeups +=09=09=09=09=09=09=09* wakeup_energy(sg) +=09=09energy_diff +=3D energy_before - energy_after +=09} + +=09return energy_diff + +Platform energy data +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +struct sched_energy has the following members: + +cap_states: +=09List of struct capacity_state representing the supported capacity state= s=20 +=09(P-states). struct capacity_state has two members: cap and power, which= =20 +=09represents the compute capacity and the busy power of the state. The=20 +=09list must ordered by capacity low->high. + +nr_cap_states: +=09Number of capacity states in cap_states. + +max_capacity: +=09The highest capacity supported by any of the capacity states in=20 +=09cap_states. + +idle_power: +=09Idle power consumption. Will be extended to support multiple C-states= =20 +=09later. + +wakeup_energy: +=09Energy cost of wakeup/power-down cycle for the sched_group which this i= s=20 +=09attached to. Will be extended to support different costs for different= =20 +=09C-states later. + +There are no unit requirements for the energy cost data. Data can be norma= lized=20 +with any reference, however, the normalization must be consistent across a= ll=20 +energy cost data. That is, one bogo-joule/watt must be same quantity for d= ata,=20 +but we don't care what it is. --=20 1.7.9.5