关于DNN的性能增强，转自http://www.dotnetnuke.com/Community/Blogs/tabid/825/EntryID/486/Default.aspx
作者：Charles Nurse (DNN核心团队成员)
Many people have commented that the dotnetnuke.com site is a little slower with the recent upgrade to 4.3.1 (especially for Login).
If your site has a lot of users, you are probably getting the same "poor" performance. (Note - the problem is not confined to 4.3.1 - it will also be a problem with 3.3.1, as it is due to one of the new User features).
However, there is a simple solution, and here it is.
1. Log in as admin or host
2. Go to the "User Accounts" module (on the Admin menu).
3. Select the "User Settings" module action
4. Click Update to save the Settings.
Savvy users will have by now figured out the problem - The User Settings, which are implemented as Module Settings in the Database do not exist (are null). Loading the User Settings page loads the default values and clicking "Update" persists them to the database.
Normally, when custom Module Settings are not "set" this does not affect performance but in this case there is a very expensive query that is run when retrieving the default settings. This query will run every time a setting is needed, because, the GetSetting uses a fallback approach:
a) - try fetching the settings from the Cache
b) - try fetching the settings from the Database
c) - load the default settings (which calls the expensive query GetUserCountByPortal)
d) - get the setting from the collection of settings
On this site, when logging in, 3 different settings are needed, so the query is made 3 times - at a cost of about 800ms each (due to 300,000 users), hence the performance issues.
Now that I have carried out the procedure above (1-4) on this site, the default settings have been persisted to the Database, and the caching mechanism can work - Login is much faster.
A fix will be added to the next version, so that default values are automaticaly saved to the database on upgrade (or first access).