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aabtop / reify

Reify lets you embed a customized TypeScript runtime within a C++ application.
MIT License
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Use V8 snapshots to decrease startup delay of TSC. #1

Open aabtop opened 4 years ago

aabtop commented 4 years ago

Startup delay for a simple TS file is not terrible right now (~100-200ms), but it's not nothing either.

This delay was introduced when moving from JS to TS. I haven't profiled it yet so it's possible that it is caused by the TypeScript compiler running on the input file, however I suspect it is more likely the fact that we're now having V8 compile the TypeScript compiler on startup each time. The TSC is ~8mb unminified and ~2mb minified.

A great example source of how to setup a V8 snapshot is given by V8's mksnapshot tool: https://github.com/v8/v8/blob/master/src/snapshot/mksnapshot.cc . This tool may work for us, but I believe it is designed to be used internally by the v8 codebase. There is a fair bit of complexity as well around how to handle cross-compilation for different CPU architectures, which is handled already in the V8 build system, but this project doesn't have direct access to that logic.

One nice compromise is to cache a snapshot on startup to a user's cache directory, so that it's guaranteed to run on the device.

aabtop commented 4 years ago

Okay, some preliminary support for caching the snapshot for the TypeScript Compiler is added in 552cef1eaf86e5a9e8d266b42d2bd83dd4b0a4de . It is disabled by default, for reasons mentioned in the commit message.

I saw the time for jeep.ts and spiral_stack.ts drop from ~750ms to ~550ms, so that's not too shabby! And this is without any kind of "warming up". I experimented with warming up the code, but didn't see a huge improvement in speed.

Added a top-level switch to make it easy to continue to experiment with snapshots in 57b81d65d25b6f16989b557a3a64325ff33c0800.

aabtop commented 4 years ago

On my laptop the time went from ~2s to ~1.65s.