I have created one report in which there is bar chart in the detail, group header and group footer section. sometimes the report runs in 7 seconds for 15 rows of data. but some times for same amount of data , chart is taking more than one minute. We conducted load test and found that if there are concurrent request then report performance is very slow.
If i remove the chart from detail section and just keep text data, report runs fine in load test also. We are using HTML 5 charts with Jasper 5.5 professional version. reports are deployed in Jasper server 5.5 commercial edition and are called from Web UI using rest API.