SSRS Extreme Slow Performance on Grouping / DrillDown Action with Internet Explorer

Question

Hi 
I have an Infrastructure with SQL Server 2012 / SSRS 2012 / VS 2012 and IE 11 and custom authentication.
Reports can be opened in reasonable time, despite when they are grouped, they are silly slow (2-10 min for 1000 records).
I've already checked the other well known topics causing the same issue with stored procedure parameters and "keep together". 
I think this could be a Internet Explorer Bug, because in SQL Server Profiler the queries are running fast (< 3sec.) and also the SSRS executionLog 2 shows fast performance. Unfortunately I can not try to compare it with another browser, because we need
the Custom Authentication Module.
Surprisingly when I group the rows, but do not use the +/- symbols for drilldown, the report is processed in zero time, as well as when I have no grouping, just plain rows... 
Any Idea? Could it be a security setting blocking something?
Cheers Lu_F

Answer 1

Hi Lu_F,
As per my understanding, there are grouping and drilldown report in the report, the report can run in reasonable time even through there is grouping, if you expand drilldown reports, the report runs very slowly.
Report server performance is affected by a combination of factors that include hardware, number of concurrent users accessing reports, the amount of data in a report, and output format. In this case, in would recommend you open the report in the Report Manager
from the Report Server machine, and check if the Drill-Down works as expected. If it works, please contact your network team to fix the network issue. By design, the Drill-Down uses JavaScript to do a postback to the report server to expand or collapse the
toggled items. If there has a network issue, the action will be a little slow.
In addition, in order to improve the performance of the report, we can split drilldown reports into parameterized drillthrough reports, because Drillthrough reports do not run until a user clicks the drillthrough link in the main report. Drilldown reports
process all data even when the data is first hidden. You can also add cache and snapshot for the report if you don’t need up-to-date results, this means that you will not see newest data until it is refreshed.
For more information, please refer to the following document:
http://technet.microsoft.com/en-us/library/dd255244(v=sql.105).aspx
http://msdn.microsoft.com/en-us/library/bb522786.aspx?
If you have any more questions, please feel free to ask.
Thanks,
Wendy Fu