I think performance of the style systems in Blink and Firefox are similar. Since Servo's style system is linearly scalable, we expect most users to get a ~4x speed improvement on styling.

Users's don't care specifically about style performance, though, but about things like interactivity. We think Servo's style system will improve those things, but don't have numbers for that on hand.

To give a concrete example, it takes Firefox ~1.2 seconds to restyle the single page HTML5 spec with it's current non-parallel style system. Firefox with Stylo can do this in ~300ms. That is close to a full second off of initial page load.

How does WebKit's JITing style system compare? (As far as I'm aware, nobody else has anything like it, though it is still single-threaded as far as I'm aware.)

I would eventually like to look into a CSS JIT. But I would not like to just copy WebKit—I would like to look into treating CSS as a global DFA and compiling accordingly instead of looking at local optimizations only.

As always, the problem with JITs, especially on the Web, that it's hard to beat the interpreter when you take compilation time into account, and most selectors you see in the wild only apply to a small number of nodes.

For context, [here's an IRC discussion about implementing style matching as a single global DFA, and what it's tradeoffs would be](http://logs.glob.uno/?c=mozilla%23servo#c550146).

Just curious, has anyone seen if there are performance improvements in Javascript DOM manipulation (eg adding elements or attributes in JS)?

How does it compare to Microsoft Edge?

Currently no major browser has significant components implemented in a safe language like Rust. And while there are some efforts towards granular parallelism in existing major browsers, none really took a "start from scratch and get it right" approach like the Servo components that Quantum intends to adopt (and that's very noticeable in Servo perf).

So on both of those aspects, the plan here is to go significantly further than any existing major browser.

Here my experience with the current Firefox compared to Chrome :

- Firefox consumes way less ressources than Chrome. I can open 20 tabs it will consume a reasonable amount of memory.

- Firefox crashes way more often than Chrome. I get a crash everyday mostly because of a aggressive Javascript found in pages riddled with ads that abuse tricks in order to force the viewser to see ads ( Adblock can help )

- Firefox is way slower when it comes to Javascript execution than Chrome, no question and it looks like it supports less HTML5 features than the competition.

If Servo can effectively limit Firefox crashes then the investment is worth it. Because that's tne most annoying thing with Firefox. But the amount of memory used by Chrome is just unacceptable, along with spawning 20 processes just because they can ... Chrome is a memory and resource hog.

I've never had my Firefox crash on me in at least a year (both on Linux and Mac OS). But I have multiple levels of adblock, so maybe it's really helping. :)

You could also try to wipe your profile and see how a frugal Firefox without any addons behaves. (Remember to backup your bookmarks to a file before wiping!)

> Firefox is way slower when it comes to Javascript execution than Chrome

If you have specific pages where you're seeing this, please file bugs on Firefox and add "bzbarsky" to the cc list for the bug!

Thanks for reaching out; will do if I encounter a case. I don't run Chrome daily, and my personal experience with Firefox is good, including with "big webapps" like Atlassian products (JIRA, Confluence), but I often read the comment that "big pages/webapps" are faster on Chrome than Firefox.

See https://news.ycombinator.com/item?id=12794971 for examples of such talk, but it's rarely precise enough to file a bug :/

Right, that's my issue. People keep claiming something is slow, but when I ask for an actual example they almost never come up with one, so I can't profile and fix it... ;)