Memory leak in setInterval + console.log + process.memoryUsage

[EricTheOne]

The following code exhibits a growth in RSS and heap over time:

setInterval(function doLog() {
    console.log(process.memoryUsage());
}, 100);

Attached image made by excel - extract measurements from above script to clipboard then:

pbpaste | grep heapTotal | cut -d " " -f 3,5,7 | pbcopy 

Why is this happening?

[JacksonTian]

process.stdout.write buffered a lot data. Not really memory leak. You can write the data into file instead of.

[bnoordhuis]

It's not necessarily indicative of a memory leak. What happens when you restrict the heap size with --max_old_space_size=32?

[EricTheOne]

@JacksonTian since I see the measurements as they come on the console, doesn't it mean the buffer gets periodically flushed?

@bnoordhuis checking

[Fishrock123]

The following code exhibits a growth in RSS and heap over time:

The graphs look normal for v8 I think. v8 like to keep as much as it can (within a specified limit, default 1gb iirc) so it doesn't have to re-allocate, is my understanding.

[trevnorris]

1.5GB for x64 machines, but @Fishrock123 is correct. V8 feels free to use the heap it's given as freely as it wants. My experience is you can only know it's a memory leak for sure if it can cause the process to crash.

[EricTheOne]

@bnoordhuis running with --max_old_space_size=32:

1. RSS - not growing (even a small decline over time)
2. heapTotal - stable
3. heapUsed - slowly increasing over time and over multiple GC runs.

@trevnorris's comment means that looking at the growth in heap utilization is not enough, so I guess this behavior is normal.

[Fishrock123]

Yeah, seems normal, that's just how newer v8 does things. Closing.