API to force garbage collection of red herring retainers like feedback_cells etc

[jedwards1211]

What is the problem this feature will solve?

I know it's not really Node's fault, but debugging memory leaks in Node has become a really shitty dev experience due to noise from things getting temporarily retained by feedback_cells, AllocationSites, etc.

I'm trying to debug memory leaks that started happening after I upgraded to Node 24 and this is making me miserable.

What is the feature you are proposing to solve the problem?

Some kind of option we can pass to global.gc() to force more intensive garbage collection.

If v8 doesn't provide an API for this, please start bugging them to provide one. I'd be happy to file an issue with them if y'all are willing to add your support to it - y'all have enough clout to make a difference here.

What alternatives have you considered?

No response

[Renegade334]

gc({ type: 'major', flavor: 'last-resort' }) is as aggressive as it gets, effectively running GC on a loop until the heap is stable.

[jedwards1211]

Okay thanks! Where is documentation of this? I wasn't managing to find it by googling. Even when googling node gc last-resort nothing specifically about that seems to come up in the official docs, but this seems like a basic necessity for debugging memory leaks. Should I make a PR to the Heap Snapshot docs to recommend using it?

[Renegade334]

The function is provided by V8's gc-extension, not part of the Node.js API. It's a flagged feature with no guarantees regarding its behaviour or availability, and I don't see that we want to be signposting users to it routinely from the API docs. However, its options are documented in V8's gc-extension header, if you want to take a look.

(For the record, this isn't an assertion that a last-resort GC will make your snapshots any easier to walk through, I'm just answering the "can we customise gc()" question.)

[jedwards1211]

As unusable as heap snapshots can be with all this noise, the V8 team would do better by its users if they provided a more stable, standardized API for collecting anything unretained by userland code.

Y'all should signpost that --expose-gc is often indispensable when working with getHeapSnapshot() and just warn that the options and availability will change over time. It's more conscientious than leaving most users in the dark about it.