feat(cli, runtime): compress snapshots

[evanwashere]

depends on denoland/rusty_v8@1cedb0e reversal
replaces v8 zlib compression with lz4 and zstd for better speed and compression ratio

build	size
deno-new	79mb
deno-uncompressed	103mb
deno-v8-compressed	80mb

deno run with cache (cli snapshot)	Mean [ms]	Min [ms]	Max [ms]	Relative
deno-new run -A b.ts	30.4 ± 0.5	29.6	32.3	1.03 ± 0.02
deno-uncompressed run -A b.ts	29.6 ± 0.4	28.9	31.5	1.00
deno-v8-compressed run -A b.ts	44.6 ± 0.5	43.8	46.6	1.51 ± 0.03

deno cache with no cache (tsc snapshot)	Mean [ms]	Min [ms]	Max [ms]	Relative
deno-new cache -r b.ts	266.5 ± 1.6	264.1	269.0	1.05 ± 0.01
deno-uncompressed cache -r b.ts	253.8 ± 1.1	252.2	255.7	1.00
deno-v8-compressed cache -r b.ts	273.8 ± 1.4	271.7	276.2	1.08 ± 0.01

deno run with no cache (cli + tsc snapshot)	Mean [ms]	Min [ms]	Max [ms]	Relative
deno-new run -r -A b.ts	540.8 ± 16.3	530.2	580.8	1.04 ± 0.03
deno-uncompressed run -r -A b.ts	519.2 ± 1.9	517.5	522.6	1.00
deno-v8-compressed run -r -A b.ts	577.4 ± 2.0	574.7	580.9	1.11 ± 0.01

test source

// b.ts
export function foo<T>(bar: T) {
  return bar;
}

console.log(foo(1));

let i = 5;
while (i--) {
  const w = new Worker(new URL(`a.ts`, import.meta.url), { type: 'module' });

  w.terminate();
}

// a.ts
let a = 1;

export function foo<T>(bar: T) {
  return bar;
}

[CLAassistant]

All committers have signed the CLA.

[ry]

1mb saved? Is it worth the complexity?

[lucacasonato]

@ry 33% improvement in startup time!

[piscisaureus]

I think this looks really good.

[bartlomieju]

LGTM

[bnoordhuis]

One question: why lzzzz instead of (lz4_flex)[https://crates.io/crates/lz4_flex]? The latter is the more popular crate and is pure Rust.

[bnoordhuis]

It's probably an academic concern but I think writing to uninitialized memory like this is technically undefined behavior. The blessed path is to use MaybeUninit: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#out-pointers

[evanwashere]

there is no undefined behavior in this case, we are just reusing previous allocation without zeroing it

[andreubotella]

I'd argue MaybeUninit is much clearer.

[andreubotella]

I've just checked, and Vec::with_capacity calls the allocator without guaranteeing that the memory has been zeroed. Sure, the allocation might've actually been reused, or it might be a new allocation that actually has been zeroed, but even if we could guarantee that it's either of those cases, I'm pretty sure the language treats the result of an allocation as uninitialized memory, which means that creating values from it, even u8 values, would be undefined behavior.

[evanwashere]

One question: why lzzzz instead of (lz4_flex)[https://crates.io/crates/lz4_flex]? The latter is the more popular crate and is pure Rust.

I initially used lz4_flex for proof of concept but switched to lzzzz because it has lz4hc and is slightly faster at decompressing cli snapshot

[bartlomieju]

@piscisaureus I guess we'll wait with landing this PR until we upgrade rusty_v8

[piscisaureus]

@piscisaureus I guess we'll wait with landing this PR until we upgrade rusty_v8

There's no need; snapshots are already off in the current version of rusty_v8.