When I use setTimeouts, often the event has already occurred. So rather than clamping, I'd suggest increasing the timeout up to 10ms rather than clamping it at the start. Thus, if I specify 0, an immediate check would occur, then move it up each time, maybe 1, 5, 10 would be optimum.
On Monday, September 29, 2008, at 10:58PM, "David Hyatt" <[EMAIL PROTECTED]> wrote: >We encountered 100% CPU spins on amazon.com, orbitz.com, mapquest.com, >among others (looking through Radar histories). This was pre-clamp. >Web sites make this mistake because they don't know any better, and it >works fine in IE. It is a mistake these sites will continue to make, >and Chrome is the only browser that will be susceptible. Being >different from IE here is not a good thing. You will end up having to >evangelize sites over and over to fix 100% CPU spins that occur only >in your browser. Do you really want that kind of headache? > >A new API will let Web apps get the performance they need while >avoiding compatibility problems. > >dave > >On Sep 29, 2008, at 10:06 PM, Maciej Stachowiak wrote: > >> >> On Sep 29, 2008, at 7:26 PM, Mike Belshe wrote: >> >>> Hi, >>> >>> One of the differences between Chrome and Safari is that Chrome >>> sets the setTimeout clamp to 1ms as opposed to 10ms. This means >>> that if the application writer requests a timer of less than 10ms, >>> Chrome will allow it, whereas Safari will clamp the minimum timeout >>> to 10ms. The reason we did this was to minimize browser delays >>> when running graphical javascript applications. >>> >>> This has been a concern for some, so I wanted to bring it up here >>> and get an open discussion going. My hope is to lower or remove >>> the clamp over time. >>> >>> To demonstrate the benefit, here is one test case which benefits >>> from removing the setTimeout clamp. Chrome gets about a ~4x >>> performance boost by reducing the setTimeout clamp. This >>> programming pattern in javascript is very common. >>> >>> http://www.belshe.com/test/sort/sort.html >>> >>> One counter argument brought up is a claim that all other browsers >>> use a 10ms clamp, and this might cause incompatibilities. However, >>> it turns out that browsers already use widely varying values. >> >> I believe all major browsers (besides Chrome) have a minimum of >> either 10ms or 15.6ms. I don't think this is "widely varying". >> >>> We also really haven't seen any incompatibilities due to this >>> change. It is true that having a lower clamp can provide an easy >>> way for web developers to accidentally spin the CPU, and we have >>> seen one high-profile instance of this. But of course spinning the >>> CPU can be done in javascript all by itself :-) >> >> The kinds of problems we are concerned about are of three forms: >> >> 1) Animations that run faster than intended by the author (it's true >> that 10ms vs 16ms floors will give slight differences in speed, but >> not nearly as much so as 10ms vs no delay). >> >> 2) Burning CPU and battery on pages where the author did not expect >> this to happen, and had not seen it on the browsers he or she has >> tested with. >> >> 3) Possibly slowing things dow if a page is using a 0-delay timer to >> poll for completion of network activity. The popular JavaScript >> library jQuery does this to detect when all stylesheets have loaded. >> Lack of clamping could actually slow down the loading it is intended >> to wait for. >> >> 4) Future content that is authored in one of Safari or Chrome that >> depends on timing of 0-delay timers will have different behavior in >> the other. Thus, we get less compatibility benefit for WebKit-based >> browsers through cross-testing. >> >> The fact that you say you have seen one high-profile instance >> doesn't sound to me like there are no incompatibilities. It sounds >> like there are some, and you have encountered at least one of them. >> Points 1 and 2 are what made us add the timer minimum in the first >> place, as documented in WebKit's SVN history and ChangeLogs. We >> originally did not have one, and added it for compatibility with >> other browsers. >> >> Currently Chrome gets an advantage on some benchmarks by accepting >> this compatibility risk. This leads to misleading performance >> comparisons, in much the same way as firing the "load" event before >> images are loaded would. >> >>> Here is a summary of the minimum timeout for existing browsers (you >>> can test your browser with this page: >>> http://www.belshe.com/test/timers.html >>> ) >>> Safari for the mac: 10ms >>> Safari for windows: 15.6ms >>> Firefox: 10ms or 15.6ms, depending on whether or >>> not Flash is running on the system >>> IE : 15.6ms >>> Chrome: 1ms (future - remove the clamp?) >>> >>> So here are a couple of options: >>> 1) Remove or lower the clamp so that javascript apps can run >>> substantially faster. >>> 2) Keep the clamp and let them run slowly :-) >>> >>> Thoughts? It would be great to see Safari and Chrome use the same >>> clamping values. >> >> Or there is option 3: >> >> 3) Restore the clamp for setTimeout and setInterval to 10ms for >> compatibility, and add a new setHighResTimer API that does not have >> any lower bound. >> >> This would let aware Web applications get the same benefit, but >> without any of the compatibility risk to legacy Web content. The >> main argument against doing things this way is that it would add API >> surface area. But that seems like a small price to pay for removing >> the compatibility risk, and turning the change into something other >> browsers would be willing to adopt. >> >> I would like to propose an API along these lines for HTML5 but I >> would prefer if we can achieve consensus in the WebKit community >> first. >> >> Regards, >> Maciej >> >> _______________________________________________ >> webkit-dev mailing list >> webkit-dev@lists.webkit.org >> http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev > > _______________________________________________ webkit-dev mailing list webkit-dev@lists.webkit.org http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
