Re: [webkit-dev] EventListener Invocation Cost?
On Jan 9, 2011, at 11:56 AM, Alex Milowski wrote: I'm not sure there is a lot that can be done about it. I’m sure we can speed it up if we have a reason to. Step one is to find out exactly where the time is spent. Then we figure out ways to streamline the code path. The experts on this may not have the same priorities you do, so they may not have plans to spend time improving it. The only question I have right now is whether the event handler function from Javascript is JIT compiled. The answer is yes. There’s nothing special about the event handler function. In fact at the time it is compiled the engine doesn’t know it will be an event handler function. Unless you’re talking about a handler from a content attribute such as onclick. Those are also compiled, though. -- Darin ___ webkit-dev mailing list webkit-dev@lists.webkit.org http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
Re: [webkit-dev] EventListener Invocation Cost?
On Mon, Jan 10, 2011 at 10:19 AM, Darin Adler da...@apple.com wrote: On Jan 9, 2011, at 11:56 AM, Alex Milowski wrote: I'm not sure there is a lot that can be done about it. I’m sure we can speed it up if we have a reason to. Step one is to find out exactly where the time is spent. Then we figure out ways to streamline the code path. The experts on this may not have the same priorities you do, so they may not have plans to spend time improving it. I will certainly spend some time trying to narrow this down but I also think my current situation is rather extreme and so I may have spoke too soon. Digging deeper into the performance of the API I'm experimenting with shows, by no surprise, that it delivers an extreme number of small event objects. There is always going to be a penalty for that but the relative performance of the execution of the event listener is actually rather good if you take the number of events delivered into account. I'm certain that a listener within C++ would perform better, but that isn't a big surprise either. When you take the overall application speed into account, things look very different. That is, not just the speed of parsing and delivering the XML information but how long does it take the application to load or use the data it has received. -- --Alex Milowski The excellence of grammar as a guide is proportional to the paucity of the inflexions, i.e. to the degree of analysis effected by the language considered. Bertrand Russell in a footnote of Principles of Mathematics ___ webkit-dev mailing list webkit-dev@lists.webkit.org http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
[webkit-dev] EventListener Invocation Cost?
I'm working on an experiment that uses EventListener instances to handle a large number of events. I've noticed there is quite a bit of overhead when invoking a Javascript-based event listener. I'm not sure there is a lot that can be done about it. I've looked through the implementation of how the Javascript function gets evaluated. The only question I have right now is whether the event handler function from Javascript is JIT compiled. I'm not sure that really matters. It seems to be the invocation which causes the most cost. If I attach an empty function for the event, the processing slows down (i.e. the cost is incurred regardless of what is going on inside the function). It just seems like the cost of crossing the language boundary between C++ and Javascript is quite expensive. I've only tried this with JavascriptCore. I've not looked into bindings for v8 as of yet. Thoughts on this? -- --Alex Milowski The excellence of grammar as a guide is proportional to the paucity of the inflexions, i.e. to the degree of analysis effected by the language considered. Bertrand Russell in a footnote of Principles of Mathematics ___ webkit-dev mailing list webkit-dev@lists.webkit.org http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
