Navigation Menu

Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Fix memory being retained until promise queue is completely empty #1544

merged 3 commits into from Sep 3, 2018


Copy link

@Shingyx Shingyx commented Aug 30, 2018

Achieved by draining each queue element in a separate function.

Resolves #1529. The issue provides a way to easily reproduce this issue.

I'm currently looking into adding a test to assert this behaviour.

Achieved by draining each queue element in a separate function
@Shingyx Shingyx force-pushed the promise-chain-memory-leak branch 4 times, most recently from 32bb36d to 15dca69 Compare August 31, 2018 12:40
Copy link
Contributor Author

Shingyx commented Aug 31, 2018

I've now added unit tests, based on the code snippet from the linked issue. It exposed a new issue when longStackTraces is enabled, where somehow the _trace is being retained after the promise is fulfilled and finishes scheduling the next promise in the queue.

I fixed this by dereferencing _trace after the promise is scheduled, to try minimise risk. Placing the dereference outside of the if (BIT_FIELD_READ(LENGTH_MASK) > 0) resulted in failing generator.js tests for some reason when running npm test, while the same tests passed when running node tools/test --run=generator.js...

Copy link

This generally LGTM but I won't have time to look at it until I'm back from holiday. Good find!

cc @petkaantonov @spion

This is because Browserify fails when parsing require("v8")
.travis.yml Show resolved Hide resolved
Copy link

Why would equal code only when called through function not cause memory leak?

Copy link
Contributor Author

Shingyx commented Sep 3, 2018

When I think about it, it's not technically a memory leak. It's more that the _drainQueue function didn't free the memory it allocated until the queue is completely drained. I'll update the title. I can update the commit messages too if you like.

I think the issue occurs because of how the garbage collector works, at least in V8. I think if memory is allocated inside the function _drainQueue, that memory will only be freed when _drainQueue completely finishes, i.e. when the queue is completely drained. By moving the memory allocation (i.e. queue.shift() and, arg)) to a separate function _drainQueueStep, then memory can be freed more often.

@Shingyx Shingyx changed the title Fix memory leak on long promise chains Fix memory being retained until promise queue is completely empty Sep 3, 2018
@petkaantonov petkaantonov merged commit f290da0 into petkaantonov:master Sep 3, 2018
@Shingyx Shingyx deleted the promise-chain-memory-leak branch September 4, 2018 06:36
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
None yet
None yet

Successfully merging this pull request may close these issues.

None yet

3 participants