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Placement Update 19-22

Welcome to placement update 19-22.

Most Important

We are continuing to work through issues associated with the spec for nested magic. Unsurprisingly, there are edge cases where we need to be sure we're doing the right thing, both in terms of satisfying the use cases as well as making sure we don't violate the general model of how things are supposed to work.

What's Changed

  • We've had a few responses on the thread to determine the fate of can_split. The consensus at this point is to not worry about workloads that mix NUMA-aware guests with non-NUMA-aware on the same host.

  • Support forbidden traits (microversion 1.22) has been added to osc-placement.

  • Office hours will be 1500 UTC on Wednesdays.

  • os-traits 0.13.0 and 0.14.0 were released.

  • Code to optionaly run a wsgi profiler in placement has merged.

  • The request group mapping in allocation candidates spec has merged, more on that in themes, below.


  • Support Consumer Types. This has some open questions that need to be addressed, but we're still go on the general idea.

  • Spec for nested magic 1. The easier parts of nested magic: same_subtree, resource request groups, verbose suffixes (already merged as 1.33). Recently some new discussion here.

These and other features being considered can be found on the feature worklist.

Some non-placement specs are listed in the Other section below.


(Numbers in () are the change since the last pupdate.)

There are 20 (1) stories in the placement group. 0 (0) are untagged. 3 (1) are bugs. 4 (0) are cleanups. 11 (0) are rfes. 2 (0) are docs.

If you're interested in helping out with placement, those stories are good places to look.


osc-placement is currently behind by 11 microversions.

Pending Changes:

Main Themes

Nested Magic

The overview of the features encapsulated by the term "nested magic" are in a story.

There is some in progress code, some of it WIPs to expose issues:

Consumer Types

Adding a type to consumers will allow them to be grouped for various purposes, including quota accounting. A spec has started. There are some questions about request and response details that need to be resolved, but the overall concept is sound.


We continue to do cleanup work to lay in reasonable foundations for the nested work above. As a nice bonus, we keep eking out additional performance gains too.

Ed Leafe's ongoing work with using a graph database probably needs some kind of report or update.

Other Placement

Miscellaneous changes can be found in the usual place.

There are several os-traits changes being discussed.

Other Service Users

New discoveries are added to the end. Merged stuff is removed. Anything that has had no activity in 4 weeks has been removed.


Making good headway.

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