Linux Plumbers Conference 2019

Session

Power Management and Thermal Control MC

10 Sept 2019, 15:00

Esmerelda/room-I&II (Corinthia Hotel Lisbon)

Description

The focus of this MC will be on power-management and thermal-control frameworks, task scheduling in relation to power/energy optimizations and thermal control, platform power-management mechanisms, and thermal-control methods. The goal is to facilitate cross-framework and cross-platform discussions that can help improve power and energy-awareness and thermal control in Linux.

Prospective topics:

CPU idle-time management improvements
Device power management based on platform firmware
DVFS in Linux
Energy-aware and thermal-aware scheduling
Consumer-producer workloads, power distribution
Thermal-control methods
Thermal-control frameworks
If you are interested in participating in this microconference and have topics to propose, please use the CfP process. More topics will be added based on CfP for this microconference.

MC leads
Rafael J. Wysocki (rafael@kernel.org) and Eduardo Valentin (edubezval@gmail.com)

Presentation materials

Etherpad notes

198. Multiple thermal zones representation

Daniel Lezcano (Linaro)

10/09/2019, 15:00

The current design of the thermal framework forces the usage of a governor with a thermal zone thus limiting the scope of the decisions.
The question of the multiple thermal zones representation and how they are handled by a governor was put several times on the table but without a clear consensus.
In order to go forward in this area, this MC topic proposes a simple design with a hierarchical...

240. Performance guarantees under thermal pressure

Morten Rasmussen (Arm)

10/09/2019, 15:25

Performance capping due to thermal limitations is common scenario particularly in mobile systems. Today user-space has no information about what level of performance that can be expected worst case and SCHED_DEADLINE can admit reservations which are impossible to fulfill.
The purpose of the this topic is to discuss what level guarantees the kernel should provide. Should the kernel have a...

245. Task-centric thermal management

Morten Rasmussen (Arm)

10/09/2019, 15:50

Thermally unsustainable compute demand is in most systems controlled by reducing performance through disabling performance states on specific CPUs or other devices in the system. It provides an efficient method to ensure the system doesn't overheat, however, it doesn't take the actual workload into account which could be better served if the performance caps were applied differently.
The...

217. Improving producer-consumer type workload performance

Srinivas Pandruvada

10/09/2019, 16:15

When each CPU core can independently control its performance states, then there is performance loss on some benchmarks compared to the case when there are no independent performance states. There are couple of options to indicate to the cpufreq drivers when a producer thread wakes a consumer thread: One sending some hints like we do for IO boost or give boost PELT utilization. But there is a...

264. Device power management based on platform firmware

Mr Sudeep Holla (ARM)

10/09/2019, 17:00

Continuing the attempts to reducing fragmentation in power management on ARM platforms, there are discussions if something similar to ACPI can be done.i.e. device centric power management.

Currently, a device has power, performance, reset, and clock domains associated with it. SCMI provides interface to deal with these domains directly. This was simpler approach to start with the SCMI...

223. Taking suspend/resume validation to the next level

Len Brown (Intel Open Source Technology Center)

10/09/2019, 17:25

At LPC 2015, we introduced analyze_suspend, a new open source tool to show where the time goes during Linux suspend/resume. Now called "sleepgraph", it has evolved in a number of ways over the last four years. Most importantly, it is now the core of a framework that we use for suspend/resume endurance testing.

Endurance testing has allowed us to identify, track, report and sometimes fix...

201. C-state latency measurement infrastructure

Artem Bityutskiy

10/09/2019, 17:50

We in Intel developed instrumentation for measuring C-state wake latency. The instrumentation, which we call "waltr" (WAke up Latency Tracer) consists of user-space and kernel modules parts.

In principle, waltr works by scheduling delayed interrupts and measuring the wake latency close to the x86 'mwait' x86 instruction. This requires an external device equipped with high precision clock and...

187. CPU Idle Time Management Improvements

Rafael Wysocki (Intel Open Source Technology Center)

10/09/2019, 18:15

There are some improvements in the CPU idle time management to be made, like switching over to using time in nanoseconds (64-bit), reducing overhead and some governor modifications (including possible deprecation of the menu governor) which need to be discussed.

356. Power Management and Thermal Control BoF Sessions

10/09/2019, 19:00