Jasper Report takes a long time to show its data

Question

I have a report which is built by Jasper Report. I use parameters for my requirement conditions. while i run my report for a small size of data (less than 100k records), it's very fast. But, the problem is while i run the data for more than 500k records. My jasper report takes so much time which cannot be predicted when exactly the finishing time is. I had increase java memory both in my local pc and my server, but it doesn't work for me. What kind of problem that occur in my report? Thanks in advance