Forcing garbage collection in Google Chrome

Question

We are developing a single-page web app with ZK which constantly communicates with server and updates parts of its screens. Updating can be as frequent as 1s. During these updates, references to large ammounts of JS objects are lost and those objects have to be cleaned by garbage collector eventually.

As far as we've figured out, Chrome only runs its garbage collector on inactive tabs. This is a problem for us, because the app's tab is usually active and almost never refreshed, thus JS objects never get collected. If left active for enough time, the tab eventually crashes (Aww Snap message).

We need to initiate garbage collection manually. So far we've tried running Chrome with --js-flags="--expose-gc" and running gc(), but it throws an exception:

ReferenceError: gc is not defined

This doesn't happen on Firefox -- memory usage is more or less a constant.

Force refreshing the page is not an option.

We would be grateful for any and all suggestions.

EDIT: we've tried running window.gc() and gc() both on Chrome versions 23.0.1271.97 m and 25.0.1364.2 dev-m

Answer 1

I found a solution. Apparently Chrome leaks DOM nodes, at least in the current version (26.0.1410.65 right now)

I recorded dev tools timeline in my app and it showed the Event Listeners count going up and down rhythmically along with my app screen's contents, but the DOM Node count was steadily increasing over time, until the tab crashed.

I tried the latest Chrome Canary (28.0.1500.3) and they seem to have fixed the problem. DOM Node count graph now follows the same rhythmic pattern as the Event Listeners.

The thing that gets me is...why doesn't gmail ever crash? I usually keep a tab open for weeks at a time...

Answer 2

In Chrome Developer Tools you have "Timeline" section, from around Chrome 53. you have there button looks like Garbage Can. clicking on it and it forcing the garbage collector to run.

Answer 3

You can fetch code of Chrome Dev Tools, modify it so that ProfilerAgent.collectGarbage(); is called every now and then (it's a code that is called when you click 'Collect Garbage' button on the Timeline panel) and run Chrome with your version of DevTools using --debug-devtools-frontend flag.

However, this solution is quite extreme, try it only when you get really desperate. Till then, I propose profiling your application and checking out why v8 decides not to clean the garbage (or can't clean the garbage). Timeline panel of DevTools will help you out with this. Start with checking if 'Collect Garbage' button at the bottom of this panel really does its job, if not - you probably have a memory leak (at least, according to v8). If so, try leak-finder-for-javascript.

[EDIT] I removed info about chrome extension, as it turns out that gc() can be called from webpage code when --js-flags="--expose-gc" is used. At least on my 23.0.1271.64.