24-28 August 2020
US/Pacific timezone

The Thing that was Latency Nice

25 Aug 2020, 09:10
Microconference1/Virtual-Room (LPC 2020)


LPC 2020

Scheduler MC Scheduler MC


Mr Patrick Bellasi chris hyser Parth Shah Dietmar Eggemann Xi Wang (Google)


The original latency nice proposal, a per-task parameter that reduced wakeup latency by short circuiting idle core/cpu searches in the wakeup path, was made over a year ago. Upstream discussion ultimately identified multiple seemingly related proposals, "Per-task vruntime wakeup bonus", "Small background task packing" and "Skip energy aware task placement". The scheduler maintainers asked the authors of the above to explore the perceived commonality and whether a single per-task parameter (formerly known as latency nice) can adequately and sensically control the intended uses. A stated constraint is that concepts like "latency nice" must be consistent with the general understanding of "nice" to include range and the direction of niceness.

A framework for evaluation was created and the four proposals are currently under discussion on the mailing list.

The goal of this proposal is to have a discussion about the main use-cases identified so far and agree on which make sense and how to progress them.

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