Start Render Time

[jarrod1937]

(06-15-2010 07:17 AM)jklein Wrote:  I could be wrong, but my understanding is that the start render time is a fixed point in time that is measuring from the initial request - this means that if your server latency goes up by 1 second your start render time will go up by one second.

In other words, the request is made at T = 0, maybe the server finishes crunching at T = 0.6, the JS/CSS downloads finish at T = 1.5, and thus the start render time is listed at T = 1.5, or 1.5 seconds. I would imagine that the start render time you are seeing (1.485s) includes the TTFB.

Your question is valid though, if you are seeing a 500ms delay between the end of the HTML download and the start of the render that wasn't there before then that is a problem. Unfortunately without access to the site or to a waterfall chart from the original site it is difficult to do further troubleshooting. Usually this kind of delay shows up because of JavaScript, but you say you don't have any inline JS and the only external request is much farther down the page. I think the bottom line is that we need access to the code in order to troubleshoot further.

Yeah, we may have to wait for pmeenan's word on this one, but when i read the "content download" figures and their associated times, i interpret that as this file took this much time to download. So, if you read the waterfall that way it means that both the html and css have been requested (which includes the time to first byte) and downloaded fully by around 900 ms. Aka:
HTML: dns lookup is 54 ms, the initial connection is 89 ms, the time to first byte (mostly server processing) is 466 ms, and the content download for it is 144 ms
CSS: the intial connection is 137 ms, the time to first byte is 211 ms and the time to download it is 2ms.
Which means that at 900 ms to 1453 ms i don't know what its doing, as at that point in time server latency should have no affect for the basic rendering of the html structure and its css styles. But who knows.

Quote:Usually this kind of delay shows up because of JavaScript, but you say you don't have any inline JS and the only external request is much farther down the page.

Yes quite true. And just to make sure i did a test without any external javascript and it still had pretty much the same start render time