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Inline JavaScript Experiment
07-13-2010, 07:32 PM
Post: #26
RE: Inline JavaScript Experiment
(07-13-2010 12:19 AM)jklein Wrote:  Couple of things:
2. Sharding static content across 10 sub-domains is probably overkill. Depending on what browsers people are typically using on your site this could cause way too much thrashing. A browser like Firefox that makes 8 connections per domain doesn't need that level of sharding (in fact it will likely make your site load SLOWER). The recommendation from Yahoo is to shard across two domains and no more. That post is also old, written when many more people were using IE 6 and 7 and we needed to be sharding more aggressively.

The Yahoo blog post stated 2 things which were limiting parallel download/sharding: CPU utilisation and DNS lookup.

The CNAME hack should hopefully mitigate the DNS Lookup penalty, though the data that has been coming back in this thread has been very interesting about its limitations. I am assuming here that this is the cause of slow down for websites with aggressive amounts of sharding?

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?

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.

Potentially the CNAME hack is only a suggestable technique for sharding up to 4-5 domains (similar to the old sharding limitation but without the added DNS penalty) and only if you are sharding on the same IP that is serving the main page. Maybe there is trick that can be done to force the browser to prefetch the DNS results for a CNAME hacked, sharded CDN when it grabs the main page? 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>
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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 - calumfodder - 07-13-2010 07:32 PM
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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