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Inline JavaScript Experiment
08-05-2010, 05:10 AM
Post: #27
RE: Inline JavaScript Experiment
(07-13-2010 07:32 PM)calumfodder Wrote:  With respects to the CPU utilisation aspect the blog poster was seeing 25% cpu utilisation downloading 2 resources and 40% for 4 parallel resources. The modern browsers have agressively upped the amount of parallel connections to 8 or more. So if CPU utilisation through parallel downloads was going to be an issue I would suggest it would be a hotter topic that it is, this is to say I don't think it is a hot topic atm but am happy to be proved wrong though. I am assuming this is the thrashing that you are referring to in your post?

Yes, that was my concern with sharding across ~10 domains. I think the reason why we don't hear about it is because very few people are sharding, and those that are usually only shard across 2-4 domains where CPU utilization is probably not an issue. Not to mention the fact that you basically have no visibility into the CPU of your clients' machines unless you are using something like WebPagetest.

(07-13-2010 07:32 PM)calumfodder Wrote:  Since modern browsers are very capable, and growing more so, my feeling is a technique like this maybe more applicable to improve matters for the army of the living dead (ie 6 users), ie7 users and other old browser users, who are limited to a small number of parallel connections, when accessing pages with a large number of resources. But while modern browsers may not experience as optimal performance as they could in a perfect world, due to potentially incurring more DNS lookups, they will still be performing faster that the old browsers, when accessing pages (using the CNAME hack) with a large number of resources....and overall your users should be getting a better experience. A lot of ecommerce sites have around 80-100 resources on a page so there is plenty of scope there for parallel downloads.

I think one important thing to know is what percentage of your users are the "living dead" as you say. If you have 80%+ using IE8/FF3+/Chrome/Safari like most sites then you really don't need to shard that much. Even if you run a complex ecommerce site 80-100 resources per page is on the high side - I work at a large online retailer and our most complex pages are in the 50-70 range. By doing too much sharding you are probably hurting the newer browsers as you help the older ones, which could be a pretty bad plan if most of your users have upgraded. Like you stated the CNAME hack has some limitations - you can run into a race condition where the nested CNAME lookup from your first DNS lookup is racing to finish while the page is racing to download the next resource on the page and making it's own DNS lookup. This would be more of a problem for newer browsers that download 6+ resources at once. In this case you really might not see the benefit from the CNAME hack.

(07-13-2010 07:32 PM)calumfodder Wrote:  Is this a case for a blocking resouce on a page just to perform DNS resolution to give benefit for non blocking resources on the rest of the page? <chuckle>

I don't have any data on this, but I'm guessing that intentionally adding a blocking resource just to allow a DNS lookup to be performed isn't a great idea. If you already have a blocking file at the top of the page though then it probably wouldn't hurt to use the CNAME hack and make that first DNS lookup fetch back the rest of the static domains on your page.
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Messages In This Thread
RE: Inline JavaScript Experiment - pmeenan - 07-10-2010, 02:50 AM
RE: Inline JavaScript Experiment - pmeenan - 07-10-2010, 05:33 AM
RE: Inline JavaScript Experiment - pmeenan - 07-11-2010, 01:42 AM
RE: Inline JavaScript Experiment - sajal - 07-12-2010, 08:04 AM
RE: Inline JavaScript Experiment - pmeenan - 07-12-2010, 02:19 AM
RE: Inline JavaScript Experiment - jklein - 07-13-2010, 12:19 AM
RE: Inline JavaScript Experiment - jklein - 08-05-2010 05:10 AM
RE: Inline JavaScript Experiment - pmeenan - 08-11-2010, 05:05 AM
RE: Inline JavaScript Experiment - jklein - 07-13-2010, 12:49 AM
RE: Inline JavaScript Experiment - pmeenan - 07-13-2010, 05:42 AM
RE: Inline JavaScript Experiment - pmeenan - 07-13-2010, 09:09 AM

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