Symptoms
Long load time for "My Tasks" standard K2 web part. Task list takes 15-30 seconds or even more at peak system usage periods (up to 3 minutes).
Diagnoses
This behavior can be observed when you have very large number of tasks in management work list (i.e. overall number of tasks for all users, let's say around 15 000 tasks)/user worklist.
Extremely large number of tasks can be cause of slow load time for worklist as in current K2 versions K2 pulls entire unfiltered worklist from the server and perform all filtering on the client side after full worklist XML blob is downloaded from the server.
With high number of tasks in your list XML blob can reach quite significant size and consequently it will take a while to be downloaded from server to client and only after download is completed filter is then applied and worklist is being displayed to the user. Hence huge amount of tasks leads to user perceivable delay in displaying worklist even with configured filter (as filter is being applied only after unfiltered worklist XML blob is download finished).
There is an existing feature request to solve this problem and perform filtering server side. According to currently available information this behavior is fixed in upcoming 4.7 release.
Apart from large number of tasks Identity cache issues may also have influence in such scenario. Based on other support cases we have seen slow performance for worklist retrieval can be caused by issues with identity cache. For example, if a user is a member of large number of AD/K2 groups this can cause very slow load time for his worklist.
In such cases it could be helpful to ensure that you have "Resolve Nested Groups" setting disabled and "Ignore Foreign Principals" setting enabled as those settings have performance impact on ADUM performance/resolving speed.
These settings can be found in K2 Workspace > Management > User Managers > K2 > Settings section.
As usual, it is also makes sense to verify your process design to make sure that best practices are taken into account in your process design. For guidelines on that please refer to: K2 blackpearl Best Practices (KB 000352).
Resolution
The only supported way of optimizing K2 worklist performance for the clients is applying filters, but as you can see from the information above it does not work well for huge worklists in current versions of K2 (entire list has to be downloaded to the client before filter can be applied).
Upcoming 4.7 release according to current information does not have filtering issue described above.
You can think about reducing number of tasks, adjusting your ADUM settings and process design or consider upgrading to 4.7 when it will be available to improve load time of task list.
