The third Operating-System-Directed Power-Management summit

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The third edition of the Operating-System-Directed Power-Management (OSPM) summit was held May 20-22 at the ReTiS Lab of the Scuola Superiore Sant'Anna in Pisa, Italy. The summit is organized to collaborate on ways to reduce the energy consumption of Linux systems, while still meeting performance and other goals. It is attended by scheduler, power-management, and other kernel developers, as well as academics, industry representatives, and others interested in the topics.

As with previous years (2018 and 2017), LWN is happy to be able to bring our readers some extensive writeups of the talks and discussions that went on at OSPM. The OSPM home page has links for slides and video of the talks. These summaries were written by Juri Lelli, Rafael Wysocki, Dario Faggioli, Marco Solieri, Claudio Scordino, Dietmar Eggemann, Valentin Schneider, Morten Rasmussen, Patrick Bellasi, Giovanni Gherdovich, Douglas Raillard, Subhra Mazumdar, Luca Abeni, Parth Shah, Volker Eckert, and Dhaval Giani. They were edited by Jake Edge.

Here is the traditional group photo from this year's event:

All of the available articles have been edited and added in below.

Day one

• Rock and a hard place: How hard it is to be a CPU idle-time governor: A talk by Rafael Wysocki about the difficulties of CPU idle-time management.
• Virtual-machine scheduling and scheduling in virtual machines: A talk by Dario Faggioli about scheduling for virtual machines versus scheduling inside virtual machines.
• I-MECH: realtime virtualization for industrial automation: A talk by Marco Solieri and Claudio Scordino about using virtualization in automation settings.
• Reworking CFS load balancing: A talk by Vincent Guittot on what is needed to rework load balancing for asymmetries between groups of CPUs.
• CFS wakeup path and Arm big.LITTLE/DynamIQ: A talk by Dietmar Eggemann on some problems with Geekbench on Arm DynamIQ systems.
• Scheduler behavioral testing: A talk by Valentin Schneider on the scheduler testing that Arm does.

Day two

• The future of SCHED_DEADLINE and SCHED_RT for capacity-constrained and asymmetric-capacity systems: A talk by Morten Rasmussen and Patrick Bellasi on problems for the deadline and realtime scheduling classes with certain kinds of processors.
• Frequency scale invariance on x86_64: A talk from Giovanni Gherdovich on handling frequency differences for per-entity load tracking (PELT) on x86_64 systems.
• How can we make schedutil even more effective?: A talk from Douglas Raillard on heuristics for skipping inefficient low-frequency operating power points on mobile platforms.
• Scheduler soft affinity: A talk from Subhra Mazumdar on a proposed soft CPU affinity feature for the kernel.
• SCHED_DEADLINE on heterogeneous multicores: A talk from Luca Abeni on changes to the deadline scheduler to support systems like big.LITTLE.

Day three

• TurboSched: A talk by Parth Shah about ways to deal with the "turbo" mode of some newer processors.
• New approaches to thermal management: A talk by Volker Eckert about using the CFS bandwidth controller for thermal management.
• Proxy execution: A talk by Juri Lelli on the proxy execution feature that is meant to be a better priority-inheritance mechanism.