What takes up space in deno?

[lukebrowell]

Genuine question, want to understand.
Js in WASM (4mb): https://github.com/mbbill/JSC.js
Stand-alone WASM runtime (4mb): https://github.com/bytecodealliance/wasmtime

There’s clearly a heap of functionality missing when comparing JS in a standalone WASM runtime to Deno. My naive question is this, what features make up the difference in binary size? Is it mostly file and network IO?

[lucacasonato]

I think this is a very interesting question:

1. We use V8, not JSC or quickjs. Why V8? It is by far the most advanced JS runtime out there. It is very fast, has a relatively expansive public API, has a WASM runtime built in, runs on pretty much every platform, has a the "V8 inspector" (used for debugging support, and line coverage), and is always very fast to adopt new ECMA features. V8 is really big (over a million lines of C++). It itself is already 10-15 MB compiled.
2. We have the typescript compiler written in JS, and SWC, a TS transpiler/bundler written in Rust built in. To make TSC start up quickly we use something called V8 snapshots. These are essentially heap dumps of V8 that can be very quickly re-hydrated to start up a new V8 isolate quickly. SWC is also relatively large (3-5MB in the final executable).
3. We have many tools like a linter, formatter, and doc generator built in. These and their dependencies add another 5-10 MB to the executable.
4. The rest of the ~50MB executable is the rest of our Rust runtime code (http client for fetch (reqwest), our event loop (tokio), and various other crates.

The actual bare minimum code required for us to execute JS (without TS support) is 32.7 MB on linux (see denort in filesize benchmark here: https://deno.land/benchmarks#executable-size).

Compared to Node we are doing very well. Node.js is 92.7 MB on Linux (v15.6.0 downloaded from https://nodejs.org/en/), and does not contain a built in linter, formatter, doc generator, coverage tool, typescript compiler and package manager. Just the Deno runtime (without tooling) is about 2.8x smaller than all of Node. Even Deno with all of its built in tooling is still 1.75x smaller than Node.

[felixf4xu]

I don't quite understand this:

The rest of the ~50MB executable is the rest of our Rust runtime code (http client for fetch (reqwest), our event loop (tokio), and various other crates.

If we create a pure rust program with those functions, will it be as big as 50M?

[nettybun]

Deno's been growing and I've been trying to distribute as-small-as-possible deno compile executables so thought I'd go poking around. Here's a screenshot of the /benchmarks?all metrics linked above since they aren't very accessible (it takes several minutes and 1.03GB of RAM to load the webpage 🏋)

I think it's ICU data and WebGPU? @lucacasonato do you know if that's what the jumps in the graph are from? I found 0cf952e which shows a 10MB ICU data payload.

I read through an article about reducing Rust binary size but learned that Deno has already enabled those size optimizations. So I'll post some findings on stripping the binaries and using cargo bloat utility in case anyone's interested and doesn't want to checkout+build Deno:

~/_/work-theirs/deno on  main [!⇣] via 🦀 v1.50.0
❯ cargo bloat --release --crates
   ...
   ...
   Compiling deno_runtime v0.9.3 (/home/today/_/work-theirs/deno/runtime)
   Compiling deno v1.8.1 (/home/today/_/work-theirs/deno/cli)
    Finished release [optimized] target(s) in 25m 02s
    Analyzing target/release/deno

 File  .text     Size Crate
13.5%  37.3%   9.7MiB rusty_v8
 4.8%  13.2%   3.4MiB [Unknown]
 2.7%   7.4%   1.9MiB std
 1.3%   3.6% 959.4KiB deno_runtime
 1.1%   3.2% 841.0KiB deno_webgpu
 1.1%   2.9% 781.7KiB deno_lint
 1.0%   2.7% 729.0KiB deno_core
 0.7%   2.0% 535.6KiB deno
 0.7%   2.0% 532.3KiB dprint_plugin_typescript
 0.6%   1.7% 454.3KiB serde
 0.6%   1.5% 410.4KiB lspower
 0.5%   1.5% 394.5KiB swc_ecma_transforms_base
 0.5%   1.5% 390.8KiB spirv_cross
 0.5%   1.4% 363.1KiB reqwest
 0.3%   1.0% 257.3KiB swc_ecma_transforms_proposal
 0.3%   1.0% 254.8KiB swc_bundler
 0.3%   0.9% 231.9KiB rustls
 0.3%   0.8% 219.5KiB naga
 0.3%   0.8% 204.5KiB wgpu_core
 0.2%   0.7% 180.7KiB clap
 4.3%  11.9%   3.1MiB And 168 more crates. Use -n N to show more.
36.1% 100.0%  26.0MiB .text section size, the file size is 72.1MiB

Note: numbers above are a result of guesswork. They are not 100% correct and never will be.

~/_/work-theirs/deno on  main [!⇣] via 🦀 v1.50.0 took 25m6s 
❯  

Doesn't tell me much but it looks like V8 is now less than the previously mentioned size of 10-15MB.

Stripping the binaries produces a 38MB executable for Linux, which is great:

73M deno*
54M deno-stripped*
53M denort*
38M denort-stripped*

[scarf005]

update 2023-08-11 for the interested:

 ~/r/deno   $-  cargo bloat --release --crates
    ...
    ...
    Finished release [optimized] target(s) in 9m 27s
    Analyzing target/release/deno

 File  .text      Size Crate
12.4%  32.5%   11.7MiB v8
 5.5%  14.5%    5.2MiB [Unknown]
 2.7%   7.2%    2.6MiB std
 2.0%   5.2%    1.9MiB deno
 1.0%   2.7% 1003.6KiB deno_core
 0.7%   1.8%  670.1KiB tokio
 0.7%   1.8%  665.1KiB deno_ast
 0.7%   1.8%  646.3KiB brotli
 0.6%   1.5%  566.9KiB deno_node
 0.5%   1.4%  506.9KiB futures_util
 0.5%   1.2%  436.1KiB deno_runtime
 0.4%   1.1%  393.3KiB deno_lint
 0.4%   1.0%  367.9KiB swc_ecma_parser
 0.4%   0.9%  340.3KiB hyper
 0.3%   0.8%  308.9KiB h2
 0.3%   0.8%  305.2KiB deno_crypto
 0.3%   0.8%  292.7KiB tower_lsp
 0.3%   0.7%  271.5KiB deno_ffi
 0.3%   0.7%  267.8KiB dprint_plugin_typescript
 0.3%   0.7%  253.9KiB deno_http
 7.4%  19.5%    7.0MiB And 281 more crates. Use -n N to show more.
38.1% 100.0%   35.9MiB .text section size, the file size is 94.4MiB

Note: numbers above are a result of guesswork. They are not 100% correct and never will be.
 ~/r/deno   $-  du -mh target/release/deno                                                                                                                                                                9.5m  2023년 08월 11일 (금) 오후 06시 24분 13초95M     target/release/deno

[felixf4xu]

if we talk about the exe file size of deno compile, it's also around 70M, I'm not sure if it's the same case, if so, can we have choice as to what we need so that the file size can be reduced if less features are enabled?

[emi0x7d1]

Deno also embeds ICU data (>10 MB) unconditionally: https://github.com/denoland/deno_core/blob/93f62f0fa2b58d781c3bd80a5abb2d94de26233b/core/runtime/jsruntime.rs#L328

Just the .rodata section of Deno core is 12.2 MB.

[jirutka]

Sigh, why does it look like Deno developers are racing to make the most bloated JS runtime ever?

[matklad]

As of today, on my linux box, deno weighs 107M against 52M for node. That is uncomfortably large for deno compile.

[mknj]

I liked the single binary approach of deno from the start.
But now it would make sense to have two binaries, one for development with all the tools and one for production that can run the compiled code(js only?).

[eternalphane]

There used to be one, but is unfortunately removed (#10350) due to its impact on CI/CD.

[bartlomieju]

It's been added back. It will be announced in Deno v1.41 release.

[walking-octopus]

Why do Linux builds still weigh 73Mb? The blog post claimed the size was reduced to 58Mb. Is an effect of some bug, out of date image or does it need some extra flag? I've verified I'm on deno 1.41.1 installed from Homebrew on Fedora atomic.

[lukasMega]

 deno --version
deno 1.44.4 (release, x86_64-pc-windows-msvc)
v8 12.6.228.9
typescript 5.4.5

my output of hello world .exe has size 123 MB (on Windows 10 x64)

Is there any information available on how to reduce the size of the output executable file?

[hansSchall]

I know that windows binaries can be a lot bigger than linux ones (deno.exe is about 98MB as of v1.45.5)

I did some testing for one of my projects and it is cheaper to have the bundled JS (<10kB) and a copy of the full Deno runtime separately, because deno compile emits a ~280MB file. This is far behind the claims of the Deno 1.42 blog post.

It doesnt look right to me that the output file is more than twice as big as bundled code + runtime.

Does this include a v8 context snapshot? If that is the case it would be great to have an option to control this.

[bartlomieju]

I suggest you open an issue about it. It indeed doesn't sound right. And yes, Deno includes a V8 snapshot of the runtime code (not user code) but it's only about 5Mb. Feels like we always use debug build for Windows which would obviously be wrong.