Speaker
Description
Following last year discussion about userspace assissted scheduling [1], schedqos utility is announced [2] and a proposal for kernel interface to help address one of the QoS issues folks see in the wild, DVFS and migration latencies, was sent also [3].
The interface proposal is a simple extension to sched_attr, but has the goal of being extensible without requiring further addition to sched_attr.
Some of the key areas to discuss:
- Deprecatability: We want to end up with baggage ABI we don't want to carry forward if internals change and a QoS no longer make sense.
- Extensibility: We want to allow almost arbitrary description of behavior without having to modify the interface.
- Discoverability: how can users know a set of QoS are available?
Currently there are two proposed users, rampup_multiplier to manage DVFS response time, and tag memory dependency between tasks for cache aware scheduling.
The latter had interesting discussions about cookie management and whether ownership should be in kernel space or userspace.
We will go through all open questions and hope to come up with a plan of what to do next.
[1] https://lpc.events/event/19/contributions/2089/
[2] https://lore.kernel.org/lkml/20260415000910.2h5misvwc45bdumu@airbuntu/
[3] https://lore.kernel.org/lkml/20260504020003.71306-9-qyousef@layalina.io/