mirror of https://github.com/nodejs/node.git
39 lines
1.8 KiB
Markdown
39 lines
1.8 KiB
Markdown
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# Node.js code cache builder
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This is the V8 code cache builder of Node.js. It pre-compiles all the
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JavaScript native modules of Node.js and serializes the code cache (including
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the bytecodes) that will be embeded into the Node.js executable. When a Node.js
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JavaScript native module is `require`d at runtime, Node.js can deserialize from
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the code cache instead of parsing the source code and generating the bytecode
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for it before execution, which should reduce the load time of these JavaScript
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native modules.
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## How it's built and used
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The code cache builder is built with the `mkcodecache` target in `node.gyp`
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when `node_use_node_code_cache` is set to true, which is currently done by
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default.
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In the default build of the Node.js executable, to embed the V8 code cache of
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the native modules into the Node.js executable, `libnode` is first built with
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these unresolved symbols:
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- `node::native_module::has_code_cache`
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- `node::native_module::NativeModuleEnv::InitializeCodeCache`
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Then the `mkcodecache` executable is built with C++ files in this directory,
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as well as `src/node_code_cache_stub.cc` which defines the unresolved symbols.
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`mkcodecache` is run to generate a C++ file
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`<(SHARED_INTERMEDIATE_DIR)/node_code_cache.cc` that is similar to
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`src/node_code_cache_stub.cc` in structure, but contains the code cache data
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written as static char array literals. Then `libnode` is built with
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`node_code_cache.cc` to produce the final Node.js executable with the code
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cache data embedded.
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For debugging, Node.js can be built without code cache if
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`--without-node-code-cache` is passed to `configure`. Note that even if the
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code cache is not pre-compiled and embedded into the Node.js executable, the
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internal infrastructure is still used to share code cache between the main
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thread and worker threads (if there is any).
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