Electron release builds are optimized with Electron-collected PGO profiles instead of Chrome's published ones. PGO profiles match functions by symbol name and control-flow hash, so Chrome's profiles cannot cover code that differs in Electron - all of Node.js, patched Chromium files, V8 built with Node's flags, and the Electron shell - and uncovered functions are laid out as cold.

Profiles are generated and uploaded by Electron's PGO generation pipeline and served from https://dev-cdn-experimental.electronjs.org/pgo/.

1. State files - <target>.pgo.txt in this directory names the profile each target uses plus its sha256, space-separated on one line (e.g. electron-linux-x64-<timestamp>-<sha>.profdata <sha256>; files written before hashes existed carry just the name). Updating a profile means updating the state file; profile binaries are never checked in.
2. Download - gclient hooks (see DEPS) run script/pgo/download-profiles.py, which downloads each state file's profile into this directory under its versioned name (the V8 builtins profile uses the fixed name electron-v8-builtins.profile, since GN args files reference it statically). When the state file carries a sha256, the downloaded bytes (and any previously downloaded local copy) are verified against it and a mismatch fails the sync - the CDN blobs are mutable, so the checked-in state file is what pins the exact profile bytes.
3. Build wiring - Chromium's standard chrome_pgo_phase = 2 machinery applies the profile. A small patch (patches/chromium/build_resolve_pgo_profiles_from_electron_state_files.patch) teaches its profile resolution to read Electron's state files - including per-arch Linux profiles, which upstream does not have - so every compiler and linker flag upstream maintains for PGO (-fprofile-use, warning suppressions, extended-TSP block layout, and anything they add in the future) applies to Electron's profiles unchanged.

chrome_pgo_phase already defaults to 2 for official builds, so no per-platform configuration is needed - any release build on any platform/arch picks up its profile automatically:

e init my-release --root=$PWD --import release
e build

The V8 builtins profile is wired separately (it is consumed by mksnapshot, not clang): release.gn points v8_builtins_profiling_log_file at the downloaded Electron builtins profile.

• Build against Chrome's published profiles: set the pgo_data_path GN arg to a Chrome profile (explicitly set paths take precedence over Electron's state-file resolution) and set checkout_pgo_profiles=True in gclient custom vars so Chrome's profile is downloaded.
• Build without PGO entirely: chrome_pgo_phase = 0.