oxidecomputer / oxidecomputer/omicron

Better CPU platform defaults

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#9,079 0 comments 1 reaction 0 assignees View on GitHub

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enhancement virtualization
Dominant language
Rust
Stars
572
Forks
97
Avg merge
2d 12h
Merged PRs (30d)
96

Description

https://github.com/oxidecomputer/omicron/pull/8728 added CPU platforms to instances and the API to set them, but a kind of underwhelming approach to picking the default CPU platform for an instance if none is specified: "the most general platform for whatever hardware the instance gets placed on". This is fine for existing Gimlet-based racks, because the most general platform on a Gimlet is also the only CPU platform a Gimlet can run, which is amd_milan.

On racks with Cosmos in them, instances will default to a CPU of amd_milan even if the only available hardware is Cosmo which can run amd_turin. Even if the rack only has Cosmo! Even if the operator intends to only ever install Cosmo (or later)!

I suspect this will fit reasonably alongside #9078, probably around Silo quotas, but I haven't thought very deeply about it yet.

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Research direction

Start with PR #8728, which added CPU platforms to instances and the API, and compare its default-selection behavior with the Silo-quota discussion in #9078. Trace how an unspecified platform is chosen for Gimlet and Cosmo hardware; done means a rack with only Cosmo hardware no longer defaults instances to amd_milan.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
backend
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
42/100

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