[iggldiggl]

Any news about the memory usage overhead this brings? The original design goal when the work on site isolation started was 1 GB overhead for a browsing session with 100 separate origins (can't remember how many tabs that was supposed to correspond to, although due to iframes it was definitively less than 100 tabs).

Was this goal reached in the end, or perhaps even surpassed, or missed after all?

I guess this also makes adblockers even more valuable in terms of saving memory, since each blocked third party-iframe that doesn't load is potentially one additional process that doesn't have to be created…

[mccr8]

I think the overhead is something more like 15MB per process, on Windows. It is higher on other OSes, due in part to the way they load executables. In practice, the total overhead is less bad than you might expect, because people usually don't have that many unique sites open. Telemetry shows that unique sites per tab decreases as the number of tabs increases.

It really depends on what web sites you have open. If you have a single tab with an ad-laden news site, the overhead will be high, but if you have a bunch of Google Docs tabs open, there's no overhead.

[iggldiggl]

Okay, so it seems the original target wasn't quite reached unfortunately.

On the other hand I guess you're right about "people usually don't have that many unique sites open", so the original design value of 100 separate origins was probably purposely chosen to be on the large side, and thinking about it, I guess not having that many unique sites open usually fits my usage patterns, too. The unknown factor I can't really judge is how many iframes with potentially separate origins the pages I normally visit use, though.

Looking at it positively, one additional potential benefit could be that I have a few long-lived tabs that I always keep open – under the current model, this means that the content processes associated with those tabs never die and possibly slowly accumulate cruft and memory fragmentation from additional tabs that happen to be loaded in them (and later closed again).

Under the new model on the other hand, closing all tabs associated with a domain should be enough to get the associated content process to exit and free up really all memory used by those now closed tabs.

[account42]

> It is higher on other OSes, due in part to the way they load executables.

Can you explain this in more detail?