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I'm investigating a memory leak in my nodejs script, by checking process.memoryUsage().heapUsed, the usage is around 3000MB.

chrome://inspect also shows memory usage of around 3000MB. However, every time after I take a heap snapshot, the heap snapshot saved reduced to around 73 MB, process.memoryUsage().heapUsed also reduced to that figure.

Anyone has a theory on how is this happening?

Jay
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It sounds like the garbage collector is running after you check the usage. Basically every once in awhile it will check to see if there is anything that isn't tied to anything anymore and will remove it, freeing up space. See this article for more details:

https://blog.sessionstack.com/how-javascript-works-memory-management-how-to-handle-4-common-memory-leaks-3f28b94cfbec

Andres
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  • Ok it appears the chrome debugger will run garbage collection when taking a snapshot. I have been using node-memwatch to monitor any 'stats' event (emitted when garbage collection run), which did not trigger when taking a snapshot with chrome for some reason. You reminded me I could have run gc manually, which solve the issues for me, thank you! – Jay Sep 05 '19 at 06:21