Rust: Windows Defender goes nuts when running rustdoc on some projects

[Jascha-N]

rustdoc gets pretty much completely stalled on some projects by Windows Defender on Windows 10. rustdoc cpu usage drops to 0%, while MsMpEng.exe uses 100% on a single core. This issue seems to have popped up only a few weeks ago.

[retep998]

rustdoc is creating thousands of files. Windows defender has to intercept each one and check whether it is okay. My recommended solution is to add the folder where you do all your rust dev to the windows defender exceptions.

As for why the issue popped up recently, it could be that rustdoc's filesystem access patterns have changed in a way that hits a pathological edge case of Defender.

[Jascha-N]

I understand and that is what I do for now. However, since cargo pulls in and compiles external crates in a subfolder of that same folder, it doesn't seem that safe. And adding exceptions for every target/.../doc folder for every project, profile and target is a complete hassle. As I've said, I've only seen this happen in the past few weeks, but that could be on me. It could very well be that I hadn't noticed it before. Thanks for the quick response.

[slimsag]

I googled a bit out of curiosity. It looks like you can submit false positives here: https://www.microsoft.com/en-us/security/portal/submission/submit.aspx

Maybe that would resolve the issue?

[retep998]

@slimsag There's no false positives here. This is simply Windows Defender slowing things down dramatically by checking files produced by rustdoc.

[slimsag]

You're totally right. My apologies -- I misread.

On Sep 5, 2016 1:52 AM, "Peter Atashian" [email protected] wrote:

@slimsag https://github.com/slimsag There's no false positives here.
This is simply Windows Defender slowing things down dramatically by
checking files produced by rustdoc.

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[Boscop]

For anyone who's interested, these are my Rust related Windows Defender excluded processes:

[kzys]

Can you reproduce the issue still? To be honest, I think rustdoc can't do much about the issue. It has to create a lot of files...

[Boscop]

@kzys What can be done is to make docs optional again: https://github.com/rust-lang-nursery/rustup.rs/issues/998
And it should be done IMO, to make updating nightlies much faster and because space is limited on Raspberry Pi.
I never used the installed docs anyway, always the online docs.
It's required to have an internet connection anyway to be able to use cargo..

[kzys]

In that case, cargo, rustup, or both of them should have the option to not install docs. Rustdoc itself can't do much.

[retep998]

The real solution here is for rustdoc to stop creating so many files! Come up with ways to merge multiple items into a single html file, so crates like winapi don't take literal hours to document.

[Boscop]

Sorry if this is too off-topic: How can I exclude ALL nightlies from causing Windows Defender to scan the files they create? I.E. all exe files under D:\Program Files\.multirust\toolchains.
It seems I can only add individual .exe files under "Excluded processes" and I can only enter directories for "Excluded files and locations" but when I add D:\Program Files\.multirust\toolchains to that category, it will only not scan the contents of that dir, but still the files created by exes in that dir!

I found this answer:
https://www.reddit.com/r/Windows10/comments/5gf38v/when_excluding_a_process_in_windows_defender_do_i/day7lz6/
But it doesn't seem to work on Win 8.1:

@retep998
Do you have an idea how to exclude all installed nightlies from Windows Defender (the files they create) on Win 8.1?

[steveklabnik]

@Boscop help questions are best posed on users.rust-lang.org