Fall cleaning: Optimizing V8 memory consumption • Hacker News Board

Re: Fall cleaning: Optimizing V8 memory consumption

#21

Post by qaq » Sat, Oct 08, 2016, 4:28 AM UTC

bmodeldotcom wrote: post #20

qaq wrote: post #2

Hope they don't adversely affect Node's performance with this tuning for low memory devices

There is no downside to keeping the overall memory arena size down: better cache locality, fewer stop the world collections. Node programmers have been asking for this behavior for years.

As mentioned in the article there is no magic latency, throughput and memory consumption are connected optimizing for one you will sacrifice a bit in the other areas.

Re: Fall cleaning: Optimizing V8 memory consumption

#22

Post by tehlike » Sat, Oct 08, 2016, 4:30 AM UTC

fenomas wrote: post #13

Piggybacking on this, can anyone recommend an approach for finding the cause of memory issues in v8? In my case I'm tuning a 3D game, and the heap usage is a sawtooth pattern with GCs about once per second. Not awful, but it would be nice to smooth it out. But playing with Chrome's various memory profiling tools I've never been able to discover where the allocations are coming from - the results always seem to be dom…

Is the game open to public? I would like to give it a look, i have done some amount of optimizations as a hobby.

Re: Fall cleaning: Optimizing V8 memory consumption

#23

Post by alooPotato » Sat, Oct 08, 2016, 4:39 AM UTC

tehlike wrote: post #22

fenomas wrote: post #13

Piggybacking on this, can anyone recommend an approach for finding the cause of memory issues in v8? In my case I'm tuning a 3D game, and the heap usage is a sawtooth pattern with GCs about once per second. Not awful, but it would be nice to smooth it out. But playing with Chrome's various memory profiling tools I've never been able to discover where the allocations are coming from - the results always seem to be dom…

Is the game open to public? I would like to give it a look, i have done some amount of optimizations as a hobby.

hey tehlike - I work on streak.com and we have some pretty interesting memory challenges being a full blown web app running inside of another very complex web app (gmail). Any interest in poking around and helping us with memory issues?

Re: Fall cleaning: Optimizing V8 memory consumption

#24

Post by fenomas » Sat, Oct 08, 2016, 5:02 AM UTC

tehlike wrote: post #22

fenomas wrote: post #13

Piggybacking on this, can anyone recommend an approach for finding the cause of memory issues in v8? In my case I'm tuning a 3D game, and the heap usage is a sawtooth pattern with GCs about once per second. Not awful, but it would be nice to smooth it out. But playing with Chrome's various memory profiling tools I've never been able to discover where the allocations are coming from - the results always seem to be dom…

Is the game open to public? I would like to give it a look, i have done some amount of optimizations as a hobby.

It's not yet, but I'm pretty sure the allocations are happening in the 3D engine I'm using. (I mean the chrome tools aren't telling me that, but when I let the game run without rendering the sawtooth goes away.)

Actually now that I take a second look, some relatively simple demos of the same engine (Babylon.js) show the same sort of behavior. Some rather trivial three.js demos do as well. I might be dealing with something that's just a fact of life for webGL rendering.

Random example (not mine) showing a vaguely similar sawtooth of heap memory usage:

http://gleborgne.github.io/molvwr/#1GCN

Re: Fall cleaning: Optimizing V8 memory consumption

#25

Post by RKoutnik » Sat, Oct 08, 2016, 5:36 AM UTC

fenomas wrote: post #13

Piggybacking on this, can anyone recommend an approach for finding the cause of memory issues in v8? In my case I'm tuning a 3D game, and the heap usage is a sawtooth pattern with GCs about once per second. Not awful, but it would be nice to smooth it out. But playing with Chrome's various memory profiling tools I've never been able to discover where the allocations are coming from - the results always seem to be dom…

Usually that's because you're creating and disposing of a lot of objects in your game loop. Look into initializing a lot of objects at the start and reusing 'em (usually called object pooling).

I'd love to take a look deeper - contact info is in my profile if you're interested.

Re: Fall cleaning: Optimizing V8 memory consumption

#26

Post by fenomas » Sat, Oct 08, 2016, 5:59 AM UTC

RKoutnik wrote: post #25

fenomas wrote: post #13

Piggybacking on this, can anyone recommend an approach for finding the cause of memory issues in v8? In my case I'm tuning a 3D game, and the heap usage is a sawtooth pattern with GCs about once per second. Not awful, but it would be nice to smooth it out. But playing with Chrome's various memory profiling tools I've never been able to discover where the allocations are coming from - the results always seem to be dom…

Usually that's because you're creating and disposing of a lot of objects in your game loop. Look into initializing a lot of objects at the start and reusing 'em (usually called object pooling). I'd love to take a look deeper - contact info is in my profile if you're interested.

Sorry if I wasn't clear, but the problem is finding the allocations, not fixing them. (They are probably happening in the 3D engine, i.e. code I didn't write.)

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.

Re: Fall cleaning: Optimizing V8 memory consumption

#27

Post by natorion » Sat, Oct 08, 2016, 6:10 AM UTC

qaq wrote: post #2

Hope they don't adversely affect Node's performance with this tuning for low memory devices

According to tests it doesn't. The heap memory optimization will only trigger on mobile devices <512MB ram. The zone memory improvements shouldn't have a negative effect.

Re: Fall cleaning: Optimizing V8 memory consumption

#28

Post by natorion » Sat, Oct 08, 2016, 6:12 AM UTC

fenomas wrote: post #13

Piggybacking on this, can anyone recommend an approach for finding the cause of memory issues in v8? In my case I'm tuning a 3D game, and the heap usage is a sawtooth pattern with GCs about once per second. Not awful, but it would be nice to smooth it out. But playing with Chrome's various memory profiling tools I've never been able to discover where the allocations are coming from - the results always seem to be dom…

There are tools with more depths: You can try about:tracing or the heap visualizer mentioned in the article.

Re: Fall cleaning: Optimizing V8 memory consumption

#29

Post by duncanawoods » Sat, Oct 08, 2016, 6:24 AM UTC

fenomas wrote: post #26

RKoutnik wrote: post #25

Earlier quoted context omitted.

Usually that's because you're creating and disposing of a lot of objects in your game loop. Look into initializing a lot of objects at the start and reusing 'em (usually called object pooling). I'd love to take a look deeper - contact info is in my profile if you're interested.

Sorry if I wasn't clear, but the problem is finding the allocations, not fixing them. (They are probably happening in the 3D engine, i.e. code I didn't write.) 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.

You are going to hate this one but its effective - divide and conquer. Just strip out features in a binary-chop fashion and rerun the memory profile. Depending on the code, it doesn't take as long as you think it will to get to small units of functionality e.g. sounds like just commenting out the 3d engine render step would be informative to you.

Re: Fall cleaning: Optimizing V8 memory consumption

#30

Post by iamstef » Sat, Oct 08, 2016, 6:56 AM UTC

fenomas wrote: post #13

Piggybacking on this, can anyone recommend an approach for finding the cause of memory issues in v8? In my case I'm tuning a 3D game, and the heap usage is a sawtooth pattern with GCs about once per second. Not awful, but it would be nice to smooth it out. But playing with Chrome's various memory profiling tools I've never been able to discover where the allocations are coming from - the results always seem to be dom…

You may want to give the follow script a try:

* https://gist.github.com/krisselden/d3ce3cbb37cc6035b0927fdbf...

It flips some handy flags providing useful output, this output can quickly illuminate issues the regular tools do not (yet).

Running this on the example you linked to bellow, shows that a series of functions are deopting and optimizing repeatedly. most likely causing at-least some of the sawtooth pattern you see.

example output (likely related to the problem):

  ```
  removing optimized code for: r.getViewMatrix]
  [removing optimized code for: r._isSynchronizedViewMatrix]
  [removing optimized code for: r._computeViewMatrix]
  [removing optimized code for: r._isSynchronized]
  [removing optimized code for: r._computeViewMatrix]
  [removing optimized code for: r._isSynchronizedViewMatrix]
  [removing optimized code for: r._isSynchronized]
  [removing optimized code for: r._computeViewMatrix]
  [removing optimized code for: r._isSynchronizedViewMatrix]
  [removing optimized code for: r._isSynchronized]
  [removing optimized code for: r.getViewMatrix]
  [removing optimized code for: r._isSynchronizedViewMatrix]
  [removing optimized code for: r._computeViewMatrix]
  [removing optimized code for: r._isSynchronized]
  [removing optimized code for: r._computeViewMatrix]
  [removing optimized code for: r._isSynchronizedViewMatrix]
  [removing optimized code for: r._isSynchronized]
  [removing optimized code for: r._computeViewMatrix]
  [removing optimized code for: r._isSynchronizedViewMatrix]
  [removing optimized code for: r._isSynchronized]
  [removing optimized code for: r.getViewMatrix]
  ```

---

note: Credit for this should go to @krisselden the author of the above gist not me.