Lazy load ext/node source code on first use #19398
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bartlomieju
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perf
mmastrac
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Jun 13, 2023
Remove `ExtensionFileSourceCode::LoadedFromFsDuringSnapshot` and feature `include_js_for_snapshotting` since they leak paths that are only applicable in this repo to embedders. Replace with feature `exclude_js_sources`. Additionally the feature `force_include_js_sources` allows negating it, if both features are set. We need both of these because features are additive and there must be a way of force including sources for snapshot creation while still having the `exclude_js_sources` feature. `force_include_js_sources` is only set for build deps, so sources are still excluded from the final binary. You can also specify `force_include_js_sources` on any extension to override the above features for that extension. Towards #19398. But there was still the snapshot-from-snapshot situation where code could be executed twice, I addressed that by making `mod_evaluate()` and scripts like `core/01_core.js` behave idempotently. This allowed unifying `ext::init_ops()` and `ext::init_ops_and_esm()` into `ext::init()`.
bartlomieju
pushed a commit
that referenced
this issue
Jun 15, 2023
Remove `ExtensionFileSourceCode::LoadedFromFsDuringSnapshot` and feature `include_js_for_snapshotting` since they leak paths that are only applicable in this repo to embedders. Replace with feature `exclude_js_sources`. Additionally the feature `force_include_js_sources` allows negating it, if both features are set. We need both of these because features are additive and there must be a way of force including sources for snapshot creation while still having the `exclude_js_sources` feature. `force_include_js_sources` is only set for build deps, so sources are still excluded from the final binary. You can also specify `force_include_js_sources` on any extension to override the above features for that extension. Towards #19398. But there was still the snapshot-from-snapshot situation where code could be executed twice, I addressed that by making `mod_evaluate()` and scripts like `core/01_core.js` behave idempotently. This allowed unifying `ext::init_ops()` and `ext::init_ops_and_esm()` into `ext::init()`.
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I'm gonna close this one for now. The trade-off between complexity and potential gains is currently not worth it to spend time on it. |
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In my understanding, WebGPU is temporarily disabled due to the lack of lazy load, are there any plans to bring it back? |
These are not the same problem - for WebGPU it's about lazy loading the Rust code (there's a startup cost related to linking system libraries on startup), while this issue was about lazy loading JavaScript code for ext/node. |
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Current we are snapshotting all internal code. One idea to improve the startup
time is to exclude "ext/node" code from the snapshot and instead load it on first
use.
The theory is that it would help us save about half of the size of the startup snapshot
and about half of the startup time.
This might require more involved changes in "core/extensions.rs" and the build
scripts.
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