4 ms·

The problem is this: Chrome. Which, last time I checked, often ends up with >100MB private working set per tab. And given the amount of dev time that's gone in

The problem is this: Chrome. Which, last time I checked, often ends up with >100MB private working set per tab. And given the amount of dev time that's gone into Chrome / Chromium, it doesn't exactly set a good precedent. Also, you're missing that there are a number of things that have to be duplicated in a multiprocess model that you only need one of in a multithreaded model. For instance: the JS heap, which has a reasonable amount of overhead. Some things can be shared between processes like they can be between threads, but not everything.

Excavator 11y ago
As far as I understand it, Firefox already have separate JS heaps since a few years back via the compartments model¹. 1: https://blog.mozilla.org/nnethercote/category/compartments/ https://blog.mozilla.org/nnethercote/category/compartments/ Edit: A quick, 100% scientific™ test: Content processes: 50 Sum: 1858.6 Max: 42.72 Average: 37.172 Content processes: 10 Sum: 791.96 Max: 88.96 Average: 79.196 Content processes: 5 Sum: 624.1100000000001 Max: 137.68 Average: 124.82200000000003 Content processes: 1 Sum: 453.89 Max: 453.89 Average: 453.89 Based on running the following script on a freshly generated about:memory profile: var max = 0; var sum = 0; var vals = $$('span[id^="Web Content"][id$="explicit"] span.mrValue'); for (let vi = 0; vi < vals.length; vi++) { let v = parseFloat(vals[vi].textContent); sum += v; max = Math.max(max, v); } console.log('Content processes:', vals.length); console.log('Sum:', sum); console.log('Max:', max); console.log('Average:', sum/vals.length); This is with ~400 tabs opened but in "unloaded" state. Only 5 pages were actually fully loaded. 50 processes caused stuttering when scrolling in the tab bar. 10 & 5 processes felt smooth and allowed tab titles of background tabs to load in quickly during startup. 1 process took forever to actually load in the tab titles of background tabs on startup. Setting changed via: about:config?filter=dom.ipc.processCount
- TheLoneWolfling 11y ago
  Compartments are not quite what I'm talking about. I'm more talking about metadata / caches. There's a fair bit of stuff that can be global with a single process that cannot be with multiple processes. Sometimes you can use shared memory tricks, but not always. Also: I wasn't aware there was that much of a memory penalty. Yow.

Excavator 11y ago

As far as I understand it, Firefox already have separate JS heaps since a few years back via the compartments model¹. 1: https://blog.mozilla.org/nnethercote/category/compartments/ https://blog.mozilla.org/nnethercote/category/compartments/ Edit: A quick, 100% scientific™ test: Content processes: 50 Sum: 1858.6 Max: 42.72 Average: 37.172 Content processes: 10 Sum: 791.96 Max: 88.96 Average: 79.196 Content processes: 5 Sum: 624.1100000000001 Max: 137.68 Average: 124.82200000000003 Content processes: 1 Sum: 453.89 Max: 453.89 Average: 453.89 Based on running the following script on a freshly generated about:memory profile: var max = 0; var sum = 0; var vals = $$('span[id^="Web Content"][id$="explicit"] span.mrValue'); for (let vi = 0; vi < vals.length; vi++) { let v = parseFloat(vals[vi].textContent); sum += v; max = Math.max(max, v); } console.log('Content processes:', vals.length); console.log('Sum:', sum); console.log('Max:', max); console.log('Average:', sum/vals.length); This is with ~400 tabs opened but in "unloaded" state. Only 5 pages were actually fully loaded. 50 processes caused stuttering when scrolling in the tab bar. 10 & 5 processes felt smooth and allowed tab titles of background tabs to load in quickly during startup. 1 process took forever to actually load in the tab titles of background tabs on startup. Setting changed via: about:config?filter=dom.ipc.processCount

TheLoneWolfling 11y ago
Compartments are not quite what I'm talking about. I'm more talking about metadata / caches. There's a fair bit of stuff that can be global with a single process that cannot be with multiple processes. Sometimes you can use shared memory tricks, but not always. Also: I wasn't aware there was that much of a memory penalty. Yow.