Frequent GC in nodejs app

[Matthew Tejo]

Hey,

I've been working on a problem our web app has. Our response times are spiking. I tracked to this down being caused by marksweep gc. Response's can take up to 6 seconds. 

I enabled gc logs and and the scavenge seems to be happening very frequently but not getting rid of anything. New objects seem to have a ~90% survival rate. Over a couple days this causes problems with mark sweep collections. These occur about every 80 seconds and take between 1.5-3 seconds. The mark sweep goes back to about the same number each time. If there was a memory leak I would think the heap size after marksweep gc would be increasing. 

We also tried setting --min_semi_space_size=24 --max_semi_space_size=500 --target_semi_space_size=250 and some larger values too. These didn't seem to have any effect. 

I'm not sure how we could get insight into what is doing all these allocations into the young memory space that cant be collected or how we could configure our app to run better. 

Thanks,

Matt