Description
The focus will be on power management frameworks, task scheduling in relation to power/energy optimization, and platform power management mechanisms. The goal is to facilitate cross framework and cross platform discussions that can help improve power and energy-awareness in Linux.
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Dietmar Eggemann (ARM), Quentin Perret (ARM)15/11/2018, 09:00
An updated proposal for Energy Aware Scheduling has been posted and discussed on LKML during this year [1]. The patch set introduces an independent Energy Model framework holding active power cost of CPUs, and changes the scheduler's wake-up balancing code to use this newly available information when deciding on which CPU a task should run.
This session aims at discussing the open problems...
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Morten Rasmussen (Arm), Patrick Bellasi (Arm Ltd.)15/11/2018, 09:25
The Linux scheduler is able to drive frequency selection, when the schedutil cpufreq's governor is in use, based on task utilization aggregated at CPU level. The CPU utilization is then used to select the frequency which better fits the task's generated workload. The current translation of utilization values into a frequency selection is pretty simple: we just go to max for RT tasks or to the...
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Rafael Wysocki (Intel Open Source Technology Center)15/11/2018, 09:50
The venerable menu governor does some thigns that are quite questionable in my view. First, it includes timer wakeups in the pattern detection data and mixes them up with wakeups from other sources which in some cases causes it to expect what essentially would be a timer wakeup in a time frame in which no timer wakeups are possible (becuase it knows the time until the next timer event and...
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Ulf Hansson (Linaro)15/11/2018, 10:10
The Generic PM domains framework (genpd) keeps evolving to deal with new problems. Lately, we have for example seen genpd to incorporate support for active states power management and also support for multiple PM domains per device. Let's walk through these new changes that have been made and discuss their impact.
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Sudeep Holla (ARM)15/11/2018, 10:55
While new technologies in platform power management continue to evolve, we need to look at ways to ensure it's independent of the OSPM. Custom vendor solutions for power management and device/system configuration lead to fragmentation.
ACPI solved the problem for some market segments by abstracting details, but we still need an alternative for the traditional embedded/mobile market. ARM SCMI...
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Srinivas Pandruvada (Intel)15/11/2018, 11:20
Due to high performance demands systems tend to be over-provisioned, where it is not possible to run at peak power of each component. Even if each component has capability to report power and set power limits, there is no kernel level framework to achieve that. IPA addresses part of it, but on the systems in question thermal limits usually are not a problem, but sudden power overdraw is a...
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Vincent Guittot (Linaro)15/11/2018, 11:45
Runtime PM allows drivers to automatically suspend devices that have not been used for a defined amount of time. This autosuspend feature is really efficient for handling bursts of activity on a device by optimizing the number of runtime PM suspend/resume calls. However, the runtime PM timers used for that are fully based on jiffies granularity which raises problems for some embedded ARM...
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Vincent Guittot (Linaro)15/11/2018, 12:05
Modern SoCs have multiple CPUs and DSPs that generate a lot of data flowing through the on-chip interconnects. The topologies could be multi-tiered and complex. These buses are designed to handle use cases with high data throughput, but as the workload varies they need to be scaled to avoid wasting power. Furthermore, the priority between masters can vary depending on the running use case like...
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