Linux Plumbers Conference 2023

Session

Power Management and Thermal Control MC

14 Nov 2023, 14:30

Presentation materials

Live Stream

93. Sensors aggregation

Alexandre Bailon, Daniel Lezcano (Linaro)

14/11/2023, 14:30

On one side a thermal sensor is associated with one thermal zone. On the other side a governor manages one thermal zone. The governor acts on a cooling device.

Some configurations have multiple sensors for the same performance domain. For instance, one sensor per core and a DVFS per group of cores.

When the energy model is used along with the power allocator, having a shared cooling...

99. New thermal trip types

Daniel Lezcano (Linaro)

14/11/2023, 14:50

Currently we have 'hot', 'passive', 'active', 'critical' trip points. The userspace needs to deal with the thermal also but in a different manner. Currently, it has to poll the thermal zone to get the temperature, thus introducing more wakes up on the system. However the sensors have now a programmable register to trigger an interrupt and the userspace may benefit that. By adding one or...

118. Use of Netlink for thermal kernel-user notification is problematic

Srinivas Pandruvada

14/11/2023, 15:10

Use of Netlink for thermal kernel-user notification is problematic

Netlink is used in thermal subsystem to notify events. This includes trip changes, temperature change, capability changes etc.
There are two notify protocols used:
NETLINK_GENERIC : Added couple of years back as the preferred kernel-user notification mechanism
NETLINK_KOBJECT_UEVENT: Used by thermal user space...

157. CPUfreq/sched and VM guest workload problems

David Dai, Saravana Kannan

14/11/2023, 15:45

This is a continuation of the similarly titled talk from last year and will focus on the remaining open items.
https://lpc.events/event/16/contributions/1195/

Running a workload on VM results in very disparate CPUfreq/sched behavior compared to running the same workload on the host. This difference in CPUfreq/sched behavior can cause significant power/performance regression (on top of...

165. VM-CPUFreq for x86: Scaling the guest frequency for performance and power savings

Mr Wyes Karny (AMD)

14/11/2023, 16:00

With the increasing size of virtual machines (VMs) and the growing deployment of workloads within VMs, power management has become a crucial aspect to optimize performance and energy efficiency. However, the absence of frequency scaling within VMs and the lack of workload utilization visibility for the hypervisor can result in suboptimal performance and power management. To address this issue,...

153. Virtualized Frequency Control for Telco Workloads

Mr Chris Macnamara, Srinivas Pandruvada

14/11/2023, 16:15

Packet processing workloads and software applications that are polling in nature bypass the typical kernel power governors. As these workloads are polling they appear 100% utilized and results in zero power savings. This solution implements a user space power governor that has visibility of the "real" workload utilization and triggers power savings. The presentation will review key components...

219. uclamp in CFS: Fairness, latency, and energy efficiency

Dietmar Eggemann, Morten Rasmussen (Arm)

14/11/2023, 16:30

Utilisation clamping enables user-space to set performance/efficiency preference per-task and task group. It is used on Android systems today but alignment with upstream Linux is lacking behind.
This a discussion topic with the aim aligning on the expectations, use-cases, and possible implementation of uclamp.

67. Make sync_state()/handoff work for the common clk framework

Stephen Boyd (Google)

14/11/2023, 17:00

There have been multiple[1] attempts[2] to implement sync_state() or handoff[3] for the common clk framework so that clks which are left enabled while booting Linux aren't disabled during lateinit when unused clks are disabled. The most common reason to do this is to display a boot splash screen until the display driver can probe and enable the clks itself. All attempts to implement a solution...

214. Intel Low Power Mode Daemon on Hybrid CPUs

Rui Zhang, Srinivas Pandruvada

14/11/2023, 17:15

Hardware vendors increasingly employ hybrid-CPU processors. Hybrid-CPU processors mix multiple CPU types within the same processor, to satisfy previously conflicting tradeoffs in power, performance, and cost.

Some hybrid-CPU processors benefit from a “low-power mode”, a non-linear power savings resulting from all work being restricted to a “low-power CPUs”, while no work runs on the...

74. Enabling DDR segments on demand during memory pressure for DDR power reduction

Sudarshan Rajagopalan (Qualcomm)

14/11/2023, 17:30

In Android systems, there is a potential for significant power consumption due to entire DDR segments being enabled even during periods of lite usage of system when only a fraction of it is actively used, thereby consuming power unnecessarily.

We can optimize DDR power consumption by selectively disabling certain segments during lite system usage and enabling them when additional memory is...

133. Improving monitoring of power saving states

Mr Stanislaw Kardach (Google), Sven van Ashbrook (Google)

14/11/2023, 17:45

ChromeOS is the second most-popular Linux distribution, designed to be long-lasting on battery and snappy, even for low-cost devices. This is achieved by leveraging various power-saving policies on multiple different platforms, including x86 (Intel, AMD), and ARM. Starting at the point of device development, we monitor and verify cpu idle, module (package/device) idle and system deep sleep...