Deno 2.5.0 reintroduces JavaScript out of memory: Ineffective mark-compacts near heap limit

[marcomow]

Version: Deno 2.5.0

Context: a large monorepo, almost exclusively written in TypeScript.
Issue: running deno check on the whole codebase causes a crash (see screenshot)

Note: we've had this issue for many versions, so we had to split the type checking into chunks; the issue disappeared in 2.4.0, so we could finally use deno check as a single command, but now the issue returned

[bartlomieju]

Have you tried increasing heap size? 2Gb heap size seems very small for working with TS in a monorepo.

[marcomow]

Thanks for the reply @bartlomieju , how do I increase it?

[bartlomieju]

You should be able to do --v8-flags=--max-old-space-size=<size in megabytes>

[marcomow]

@bartlomieju it looks like deno check doesn't support this flag? 🤔

[haturatu]

@marcomow

maybe

deno check -- . --v8-flags="--max-old-space-size=8192"

#18935

https://docs.deno.com/runtime/getting_started/command_line_interface/

[bartlomieju]

Ugh, that looks like an omission... Can you try deno run --check --v8-flags=--max-old-space-size=....

[marcomow]

thanks @haturatu , but that's a runtime flag (you're proposing using it as an argument)

@bartlomieju I can confirm deno run works, but deno check results in the error of the screenshot above

[bartlomieju]

Right, so that's a problem with the default heap size. I think we should do the same thing we do for deno lsp which is to set default heap size to the system limit.

[bartlomieju]

@marcomow how much memory did you specify in that command?

[marcomow]

8000 and 8192, but no matter what I specify the issue is that --v8-flags is not accepted as runtime argument by deno check

[bartlomieju]

8000 and 8192, but no matter what I specify the issue is that --v8-flags is not accepted as runtime argument by deno check

Yeah I understand that, but deno run --check --v8-flags=... should be equivalent (ie. it will first type check the code and the execute it). So if the type checking doesn't fail in that deno run subcommand we'll know how much memory you need to type check.

[marcomow]

I'm not sure how to run that command, because deno run expects an entry point, whereas deno check can be run without...
but in our repository there are a ton of services, that are run separately. But we want the check to be global to ensure consistency. Hope I've expressed myself properly

[bartlomieju]

Doh... @marcomow you can do DENO_V8_FLAGS=--max-old-space-size=<size> deno check (we accept an env var in addition to the flag).

[bartlomieju]

@marcomow which OS are you running on?

[tusharrrr1]

Add DENO_V8_FLAGS=--max-old-space-size=8192 to your shell profile (.bashrc, PowerShell profile, etc).

If you’re using CI, configure the environment variable there.

I can create a PR if you want, allow me to work on it