Current time: 11-21-2019, 11:55 PM Hello There, Guest! (LoginRegister)

Post Reply 
 
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Incorrect display of "Time to First Byte" in waterfall ?!
12-06-2012, 06:34 PM
Post: #4
RE: Incorrect display of "Time to First Byte" in waterfall ?!
I had a second look at the problem and noticed, that the "Start Offset" seems to affect the confusing display of the waterfall.

Have a look at the attached picture...

I tried to compare the HAR Files from the webpagetest.org measurement vs. the HAR File from our server.
Afterwards I tried to understand how the "Start Offset" is calculated.
I think it works like this:

{"log":{"version":"1.1",
"creator":{"name":"WebPagetest",
"version":"1.8"},
"pages":[{"startedDateTime":"2012-12-04T09:50:40.000+00:00",(A)
"title":"Run 1, First View for ",
"id":"page_1_0",
"pageTimings":{"onLoad":6098,
"onContentLoad":-1,
"_startRender":2118}},

{"startedDateTime":"2012-12-04T09:50:56.000+00:00",
"title":"Run 1, Repeat View for ",
"id":"page_1_1",
"pageTimings":{"onLoad":1570,
"onContentLoad":-1,
"_startRender":1563}}],
"browser":{"name":"Google Chrome",
"version":"23.0.1271.95"},

"entries":[

{"pageref":"page_1_0",
"startedDateTime":"2012-12-04T09:50:41.308+00:00",(B)
...
(B) –(A) =1.308 sec



If you look at the picture, the TTFB bar at wpt.org startes exactly at the "Start Offset", which is 1,308 sec.
In our case the "Start Offset" is 0,220 sec and I think the TTFB also is painted from 0,220 sec to 2,371 sec. It looks like the problem is, that because the "Start Offset" is smaller then the value of "connect", the TTFB bar is partly covered by the bars for "Initial Connection" and "SSL Negotiation".
If that is the case, the total time calculated (3394 ms) would be wrong and should be Start-Offset + TTFB = 2371 sec.

What do you think about this?

Thanks in advance.

Regards,

Kai


Attached File(s) Image(s)
   
Find all posts by this user
Quote this message in a reply
Post Reply 


Messages In This Thread
RE: Incorrect display of "Time to First Byte" in waterfall ?! - KaiBra - 12-06-2012 06:34 PM

Forum Jump:


User(s) browsing this thread: 1 Guest(s)