Load Time on asp.net page cannot be accounted for

Question

I am trying to find where my load time is being consumed. I have added tracing to almost everything I can think of and there is a missing 200ms ( which is more than 50% of the total load)

How can I account for this missing time

 Description                        Duration(ms) with Children(ms)  from start(ms)
  http://localhost:80/default.aspx   320.8        357.3              +0.0
  CreateControlCollection            0.0          0.0                +27.2
  OnPreInit                          0.1          0.1                +27.2
  GetVaryByCustomString              0.0          0.0                +227.0
  Control OnInit                     0.0          0.0                +232.4
  Control OnInit                     0.0          0.0                +232.4
  Control OnInit                     0.0          0.0                +234.2
  Control OnInit                     0.0          0.0                +234.2
  Control OnInit                     0.0          0.0                +234.2
  GetVaryByCustomString              0.0          0.0                +234.6
  Control OnInit                     0.0          0.0                +234.9
  Control OnInit                     0.0          0.0                +234.9
  GetVaryByCustomString              0.0          0.0                +235.0
  GetVaryByCustomString              0.0          0.0                +235.3

Answer 1

It looks like the unaccounted-for time is being consumed between PreInit (a page-only event) and Init for a control. A few ideas:

1. Control initialization is a possible culprit. The control Init event is fired after control initialization is complete, not before.
2. Are you using ASP.NET themes or skins? If so, they are applied between PreInit and Init.
3. Keep in mind that Init events are fired bottom-up; children before parents.
4. Threading issues are a possible cause of time gaps. Are your measurements from an otherwise idle system? Are there any I/O operations happening early in the page life cycle?
5. Are you using master pages? If so, keep in mind that they are implemented as a child control of the page.