One suspects that DevTools' memory profiling should be the place to start, but I haven't found any way to get it to shed any light on where allocations are occurring. So that's what I'm asking about here.
With that said, do you have any advice on how to use it in practice? Timeline profiles tell me my app goes through maybe 5MB of heap per second, but when I use this feature for say, 5 seconds, it tends to report 2-3 functions as having allocated 16kb each. (And if I run it again, I get similar results but with a different 2-3 functions.) Is it just reporting a very small subset of allocations?
If you want to look at all the allocations during the interval, then you can use the 'Allocation timeline' profile – this will give you all the allocations but note that this might have significant overhead.
(I mean, not to suggest that what you describe isn't useful - I'm just hoping to use profiling tools to attack from a different direction.)
>> not so easy to jump into a three.js-sized chunk of 3rd party code and find atomic things that can be turned off
Incidentally, doing a dissection like this is actually an engaging way to learn a big chunk of 3rd party code compared to just staring at it. By stubbing out various pieces you learn where the joints are where things are entangled nests of sorrow.