http://summit.ubuntu.com/lpc-2012/ Constraint Framework

Wednesday 10:45 - 11:30 PDT
Not Attending PM Constraints: Intel
Power Management Constraints Topics: 1) Power vs. Performance 2) Priority Based PM QoS Constraints Framework === Power vs Performance === In order to suffice problems related to a "minimum" quality of service for basic HW like CPU/networking/DMA, we have the existing PM QoS framework to solve our problems. As the discrete HW units grow on a SoC, so IMO should the PM QoS layer scale. The second part of the problem is the scaling "up" or "down". We can mirror the PM QoS constraints to Perf QoS constraints which would allow independent devices to scale the generic system upwards into the performance mode. The performance QoS can also be used by platform specific constraints like thermals to either throttle device/SoC features OR constraints like accelerated workloads that may require a minimal CPU/SoC operating point to scale SoC features. Examples include issue faced on memory throughput on TI platforms, increasing CPU frequency as discussed in mailing lists by NVidia developers, imposing constraints on devices like CPU/LCD for thermal management etc. Topic Lead: Sundar Iyer Worked/Working on PM/tunings/efficiency for Linux in ST-E/Intel === Priority Based PM QoS Constraints Framework === There are workloads that require certain CPU Freqs, these Workloads should be able to tell the system what Freq is the optimal freq. But there may be thermal constraints that should not be allowed to be breached which requires Freq throttling or a user may want to artificially throttle or bump up the Freq all these Freq constraint requirements becomes difficult to manage since now we have a problem of which of those to be selected. In order to solve this problem, we propose a priority based PM QoS for Freq Management. High Priority Constraints may be reserved for thermal Throttling, Medium for user throttling or bump up, and Low for process PM QoS constraints Topic Lead: Illyas Mansoor Illyas works in Power Management Domain in Intel, specifically contributed to Intel SoC Power Management Linux Kernel

Participants:
attending apm (Antti P Miettinen)
attending lorenzo-pieralisi (Lorenzo Pieralisi)
attending mark97229 (Mark Gross)

Tracks:
  • Constraint Framework
Nautilus 4
Thursday 16:30 - 17:15 PDT
Not Attending PM Constraints: OMAP
Power Management Constraints - OMAP 1) OMAP SoC Thermal Containment 2) Power Management in Linux with a coprocessor 3) New Model for System and Devices Latency === OMAP SoC Thermal Containment === The thermal challenge is to design an end-product with high performance while keeping the junction temperature of the IC components used on this product within their limitations and which does not present a thermal discomfort for the user. OMAP4/OMAP5 System on Chips, operating at highest Operating Performance Points (OPP), is a powerful mobile applications processor. However operating at higher voltage and higher frequency in a sustained manner may cause thermal limits to be exceeded, both for silicon and user comfort. We propose extensions on existing frameworks to model per device power constraints, for containment of thermal limitations across major heat sources of a end-product device, e.g. LCD, CPU, charging, etc. The framework shall facilitate the power and thermal management performed by governor and policies, depending on device context and use case knowledge. Topic Lead: Eduardo Valentin Eduardo currently acting as System Software Engineer at Texas Instruments, working on OMAP Linux kernel. He has been involved with embedded Linux for some years already, contributing on products of companies like Texas Instruments, Nokia, Motorola and Samsung. The main areas of interest are (not limited to): power management, real time, performance, scheduling, system and software otimization, and recently, thermal management. === Power Management in Linux with a coprocessor === Shutting down the main processor of an SoC in the idle and standby state results in significant power savings. However, doing so requires the responsibility of reviving the system to be passed onto an independent entity in the system. Texas Instruments has taken the lead in introducing a novel approach for system power management in its AM335x processor family involving a Cortex-M3 to assist the main processor. In the future there will other devices from Texas Instruments and possibly other silicon vendors which adopt this technique. Integrating a co-processor which is not running Linux with the PM framework comes with a new set of challenges. The co-processor needs to interact with the host processor for idle as well as standby power management. How do we communicate with a co-processor without significant overhead in the idle thread? In case the co-processor stops responding what should be recovery mechanism in the PM framework? What should be the mechanism for exporting the core details like the configured wakeup sources to the co-processor? This session will focus on the above mentioned challenges and other issues surrounding the usage of a co-processor for power management in Linux. Topic Lead: Vaibhav Bedia Vaibhav Bedia, Software Systems Engineer, Texas Instruments, works on Linux kernel development for Sitara ARM microprocessors. === New Model for System and Devices Latency === Due to the nature of the new SoC architectures the Power Management needs a new model for the various system latencies. The session discusses: - Concepts of system, devices, wake-up and resume latencies, - Recent changes in the devices framework for the latency, why and how to make it generic, - Links with the other PM QoS frameworks: thermal, cpuidle, - Recent changes in the ARM/OMAP platform code for the system latency, - Problems encountered while modelling and measuring the various latencies, - A proposed model and how to implement it, - Planned changes in the device framework, the platform code and the APIs. This session is oriented towards Linux power management developers. The goal is to agree on a framework implementation and the interfaces within the kernel and with the user space. Topic Lead: Jean Pihet <email address hidden> Jean is working with embedded Linux since many years now, for companies like Texas Instruments, MontaVista, Motorola and Philips. Recently NewOldBits.com has been founded to provide high quality consulting services. The area of work is mainly OMAP Power Management, tracing and profiling tools (perf, ftrace, oprofile...) for recent ARM cores.

Participants:
attending apm (Antti P Miettinen)
attending mark97229 (Mark Gross)
attending srwarren (Stephen Warren)

Tracks:
  • Constraint Framework
Nautilus 5
Friday 11:00 - 11:45 PDT
Not Attending PM constraints: Tegra
NVIDIA Tegra power management features DVFS, sleep states and switching between low power and high performance CPU clusters. In the current Linux kernel the central subsystems affecting the state of CPUs are cpuidle, cpufreq and CPU hotplug. We propose a new framework, cpuquiet, for coordinated control of CPU cores allowing migration between CPU clusters, maximizing available performance in the presence of EDP and thermal constraints and maximizing the utilization of low power states in the presence of CPU power state constraints and discuss how PM QoS could be extended to allow more efficient power management utilizing e.g. device context and application knowledge to guide the behavior of the different subsystem governors. Topic Lead: Antti P Miettinen Energy Efficiency Engineer at NVIDIA, working on Tegra Linux kernel, previously a mobile device power management researcher at Nokia Research Center. Topic Lead: Peter De Schrijver NVIDIA Tegra Linux kernel engineer, Debian developer, previously working on power management in maemo for Nokia.

Participants:
attending apm (Antti P Miettinen)
attending mark97229 (Mark Gross)
attending srwarren (Stephen Warren)

Tracks:
  • Constraint Framework
Nautilus 3

PLEASE NOTE The Linux Plumbers Conference 2012 schedule is still in a draft format and is subject to changes at any time.