[webkit-dev] Question regarding priorities of subresource content retrieval

[Adam Barth]

On Mon, Feb 7, 2011 at 12:18 PM, Silvio Ventres
<silvio.ventres at gmail.com> wrote:
> The function doesn't seem to get any information regarding domain the
> resource is hosted at.
>
> Calling some kind of setResourceDomainType() to set DOMAIN_TYPE to
> enum(0=main domain, 1=subdomain within same domain, 2=CDN, 3=external
> domain) and then providing that as an additional parameter to
> defaultPriorityForResourceType() seems logical. Trying to see where
> this domain-sensing function can be called at earliest.
>
> Regarding the performance test, since it depends on multiple resources
> with highly differing latency, it would depend on an external
> resource. Does the PerformanceTest framework have some kind of latency
> simulator?

There is no PerformanceTest framework that deals with network latency.
 Please feel encouraged to build one.  :)

Adam


> On 2/7/11, Nate Chapin <japhet at google.com> wrote:
>> The default prioritization is found here:
>> http://trac.webkit.org/browser/trunk/Source/WebCore/loader/cache/CachedResource.cpp#L51.
>> There are cases where we override this (e.g., I'm pretty sure we load
>> favicons at a lower priority than other images)
>>
>> On Mon, Feb 7, 2011 at 11:44 AM, Adam Barth <abarth at webkit.org> wrote:
>>
>>> There is already some amount of code that's involved with prioritizing
>>> subresource loads.  See
>>>
>>> http://trac.webkit.org/browser/trunk/Source/WebCore/loader/ResourceLoadScheduler.h
>>> and
>>> http://trac.webkit.org/browser/trunk/Source/WebCore/loader/cache/CachedResourceLoader.h
>>> .
>>>
>>> I suspect the prioritization algorithm could be improved.  A good
>>> first step is to create a benchmark illustrating the performance
>>> issues and then write patches that optimize the benchmark.  Please
>>> consider putting your performance test in
>>> http://trac.webkit.org/browser/trunk/PerformanceTests/ so that it's
>>> easy for others to work on as well.
>>>
>>> Adam
>>>
>>>
>>> On Mon, Feb 7, 2011 at 11:23 AM, Silvio Ventres
>>> <silvio.ventres at gmail.com> wrote:
>>> > Hello.
>>> >
>>> > Can someone point where in the source code is the implementation of
>>> > the subresources loading and some documentation regarding its
>>> > implementation - as a queue or just child-threads or async functions?
>>> >
>>> > The reason is that the current subresource loading seems to lack any
>>> > prioritization and it often occurs that some external "1x1 pixel
>>> > tracker" or other similarly unimportant page resources block the
>>> > rendering of the page completely, and the user is left starting at
>>> > "contacting ads.doubleclick.com" with a blank page. This is very
>>> > frustrating as the page render as a whole then depends on the slowest
>>> > part and cannot be possibly done faster by any optimizations in
>>> > hardware or software on the part of the page owner.
>>> >
>>> > Thus, the proposition is this:
>>> > 1. Render should only wait for the main HTML/CSS to load from the main
>>> > page domain (a page in tumblr.com domain should wait for html/css
>>> > files from *.tumblr.com, but not from *.doubleclick.com).
>>> > 2. Other content load except HTML/CSS should be prioritized as
>>> > follows, with placeholders shown until the load is complete - possibly
>>> > adding one or more extra render passes, but increasing interactivity.
>>> >
>>> > So, basic priorities:
>>> >
>>> > 10 = Highest:   HTML/CSS from main domain (
>>> sites.tumblr.com/some_site.html)
>>> > 9: JS/XHR from main domain
>>> > 8: HTML/CSS/JS from subdomains in the same domain (
>>> ads.tumblr.com/ad_serve.js)
>>> >
>>> > 7. <Reserved for future use>
>>> >
>>> > 6. IMG/media from main domain (sites.tubmlr.com/header.png)
>>> > 5. IMG/media from subdomains in the same domain (
>>> ads.tubmlr.com/banner1.png)
>>> >
>>> > 4. <Optional*> HTML/CSS/JS (text) from CDNs
>>> > 3. <Optional*> IMG/media from CDNs
>>> >
>>> > 2. HTML/CSS/JS from other domains
>>> > (*.doubleclick.com/link_210986cv3.php?refer=2323424)
>>> > 1=Lowest. IMG from other domains (*.doublclick.com/images/track_1x1.gif)
>>> >
>>> > *4 and 3 are optional and would need some kind of a whitelist of
>>> > well-known CDN domains.
>>> >
>>> > This prioritization will reduce the latency between the page load
>>> > start and a usable render, so even if some external-domain subresource
>>> > is nonresponsive, interactivity will not suffer.
>>> > Maybe the priorities should be moved to a user-controllable setting,
>>> > where more fine-grained rules can be defined. Otherwise, maybe HTML
>>> > standard can be extended to provide hints to the browser regarding the
>>> > preferred subresource loading order, which should of course be
>>> > user-overridable.
>>> >
>>> > Thank you for reading.
>>> > This might be a big undertaking but the benefit for the user will be
>>> > seen instantly.
>>> >
>>> > --
>>> >  silvio
>>> > _______________________________________________
>>> > webkit-dev mailing list
>>> > webkit-dev at lists.webkit.org
>>> > http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
>>> >
>>> _______________________________________________
>>> webkit-dev mailing list
>>> webkit-dev at lists.webkit.org
>>> http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
>>>
>>
>