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Add draft field note: sccache compile cluster on Chromium (build-cluster-chromium) - #465

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Add draft field note: sccache compile cluster on Chromium (build-cluster-chromium)#465
jetm wants to merge 3 commits into
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field-notes/build-cluster-chromium

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@jetm jetm commented Jul 21, 2026

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Draft Field Note: a measurement-first look at where a compiler-cache cluster actually speeds up a Yocto build. Structured draft with [ENGINEER:] placeholders, reviewed here on the PR (not merged) per the field-notes CONTRIBUTING.

Angle (the honest spine)

  • Chromium (a single compile-bound package) built from scratch on a two-machine sccache-dist cluster (PC1 + PC2): the big win. The numbers are [ENGINEER:] until the demo is recorded.
  • A full image barely moves: measured ~1.12x / ~11% (3h28m -> 3h06m, cold qemuarm64), because Yocto cold builds are latency/configure-bound. Stated plainly as "don't read the Chromium number as a whole-build number."
  • Making the whole build considerably faster is a different lever (a proper shared NFS SSTATE_DIR/DL_DIR/ccache), teed up as a separate future note.

Upstreaming

Ties the note's "what broke" to the public fixes we are landing on mozilla/sccache: RFC #2775 plus Wave-1 PRs #2776 and #2777, with later waves summarized.

Not ready to un-draft

  • draft: true (excluded from the production build); 11 [ENGINEER:] placeholders remain.
  • Blockers: record the two devtool demo Chromium runs (one machine vs the cluster), confirm the cluster is clearly faster, fill the placeholders, embed the MP4s.

Verification

  • yarn build is not the gate for this change yet: the note is draft: true, so Docusaurus excludes it from the production build. The MDX structure mirrors _template.mdx and the existing notes; full build validation applies when it is un-drafted.
  • No bakar references; no customer names (checked).

Tracks ENG-2174.

Copilot AI review requested due to automatic review settings July 21, 2026 18:22

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Pull request overview

Adds a new draft Field Note documenting measurement-driven results from using a two-machine sccache-dist compile cluster to accelerate Yocto builds, emphasizing the difference between a single compile-bound package (Chromium) vs. an end-to-end image build.

Changes:

  • Introduces a new draft Field Note MDX post with [ENGINEER:] placeholders for pending measurements and demo embeds.
  • Documents observed outcomes and constraints (compile-bound vs configure/latency-bound behavior) and frames follow-on work.
  • Links the “what broke / what we’re upstreaming” section to public mozilla/sccache tracking (RFC #2775 and PRs #2776/#2777).

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Copilot AI review requested due to automatic review settings July 21, 2026 18:32
@jetm
jetm force-pushed the field-notes/build-cluster-chromium branch from 41888f0 to a4a5828 Compare July 21, 2026 18:32

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Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

…ter-chromium)

Structured draft (draft: true) with [ENGINEER:] placeholders for the
recorded Chromium demo numbers and the feed package count; it stays on the
branch until the demo is recorded and the placeholders are filled. Frames
the compiler-cache cluster honestly (big on the compile-bound package,
~11% on a full image) and links the mozilla/sccache upstreaming. Tracks
ENG-2174.

Signed-off-by: Javier Tia <javier@peridio.com>
Copilot AI review requested due to automatic review settings July 21, 2026 18:45
@jetm
jetm force-pushed the field-notes/build-cluster-chromium branch from a4a5828 to f577c5a Compare July 21, 2026 18:45

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Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

Comment thread src/field-notes/2026-07-21-build-cluster-chromium.mdx
Comment thread src/field-notes/2026-07-21-build-cluster-chromium.mdx Outdated
TestStatus renders whatever `cli` receives under a hard-coded "Avocado CLI"
label. This note passed a build-tooling version into it, so the rendered
strip would have claimed an Avocado CLI version the note never tested
against - and the value is a placeholder, so the wrong label would have
survived the fill-in pass unnoticed. The build-tooling version is already
carried by `tested_against` and the prose, which is where a build note's
toolchain belongs; the component offers no field for it.

Also repair the frontmatter description, which read "speeds up a
from-scratch build - large on compile-bound Chromium". That trailing clause
has no subject to attach to, and the description is what search results and
the field-note index show, so it is the one sentence that has to parse
standing alone.

Signed-off-by: Javier Tia <javier@peridio.com>
Copilot AI review requested due to automatic review settings July 28, 2026 00:25
The drafting note pointed the engineer at a named local build workspace and
at the internal tool used to capture the recordings. Both sit in the public
docs repo from the moment the branch is pushed, and `draft: true` only keeps
the page out of the published build - it does not keep the source out of the
repo. The path also leaks internal repo naming for no reader benefit.

The instruction does not depend on either detail: what the next person needs
is which two runs to record and which numbers to lift off the timers, so say
that and drop the rest.

Signed-off-by: Javier Tia <javier@peridio.com>

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Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 1 comment.

Comment thread src/field-notes/2026-07-21-build-cluster-chromium.mdx Outdated
Copilot AI review requested due to automatic review settings July 28, 2026 00:31

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Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

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