- From: Jonas Sicking <jonas@sicking.cc>
- Date: Wed, 27 Jan 2010 17:57:52 -0800
- To: Zhiheng Wang <zhihengw@google.com>
- Cc: public-webapps@w3.org
On Wed, Jan 27, 2010 at 5:30 PM, Zhiheng Wang <zhihengw@google.com> wrote: > Hi, Jonas, > Thanks for the comments. pls find comments inline. > On Wed, Jan 27, 2010 at 12:12 AM, Jonas Sicking <jonas@sicking.cc> wrote: >> >> On Tue, Jan 26, 2010 at 11:39 PM, Zhiheng Wang <zhihengw@google.com> >> wrote: >> > Folks, >> > Thanks to the much feedback from various developers, the WebTiming >> > specs has undergone some >> > major revision. Timing info has now been extended to page elements and a >> > couple more interesting timing >> > data points are added. The draft is up >> > on http://dev.w3.org/2006/webapi/WebTiming/ >> > Feedback and comments are highly appreciated. >> >> I take it the idea is that you can get when we for an <img> element >> start fetching the image, when image data starts arriving etc. I'd >> prefer if the spec had a comprehensive list of elements that this is >> expected to be implemented on. > > Right now only embedded content elements require these info. An explicit > list > might be better though, e.g., <script> is not classified as embedded > content. What do these properties measure on a <figure>? And why would you care to measure downloading performance on <link rel=icon>? And why wouldn't you care about <script>? That one seems more performance critical than any other external resource. >> Extending this to elements introduces *significantly* more >> implementation cost. Is it really worth it? My concern is that this >> spec already had fairly high cost/benefit ratio since it doesn't add >> any "new" functionality to the web platform, it "just" lets devs do >> more accurate performance measurements. And it's far from easy to >> implement since much of the information isn't available outside of the >> networking code (and many times there only available on a different >> thread). > > Certainly the overhead of implementing the specs should be evaluated. It > should be > done while we are looking into more browser-specific implementations. Right > now I want > to be as specific as possible in the specs. But much implementation overhead > can be > avoided if we can tune the specs to accept some slight "inaccuracy", say, > taking the time > of the first callback from the data socket instead of the actual first > byte time as responseStart. I'm not sure what you mean by "more browser-specific implementations"? Implementation complexity vs. value should be looked at all the time IMHO. >> Also, what is the use case for the "Ticks" interface? > > The Ticks interface is a convenient way to store time measurements and > retrieve it later on a page. > I will have some example there. Why not just do: myTimings = {}; myTimings.fooStart = new Date(); etc? Javascript has perfectly good ways to store values already. >> I would really encourage that this spec be reduced to the most >> important parts first and wait for browsers to catch up before adding >> "nice to have" features. > > Agree and we do keep that in mind. Most of the the properties specified > right now are > on the critical path of user perceived latency though. That surprises me. See my first answer above. >> If implementations implement progress events on the various elements >> it would seem like you would get most of the advantages from this >> spec. > > The progress events are great, except that they mostly focus on > downloading the content but > not much about everything else, say, parseStart. Specs can be changed, nothing is set in stone :) / Jonas
Received on Thursday, 28 January 2010 01:58:46 UTC