Unresponsiveness when having 4000 over records with grouping

[TeeJT]

I am facing this problem - when I have to show over 4000 records with grouping - the grid is so unresponsive that my Chrome browse will complain about the unresponsiveness and asks me whether to kill the page or wait for the task to end. My table has only 3 columns. This dialog appears a few times.
But as I need all the data to print the document, what can I do to make the table more responsive?

[paramvir]

if you have implemented custom summary, then you might need to look into it to make it fast and remove any inefficiency.

In our tests, it takes only a fraction of a second while grouping with around 10,000 records and 3 levels of grouping.