I'm encountering an issue with the Mapreduce HistoryServer processing the history files for large jobs. This has come up several times with for jobs with around 60000 total tasks. When the HistoryServer loads the .jhist file from HDFS for a job of that size (which is usually around 500 Mb), the HistoryServer's CPU usage spiked and the UI became unresponsive. After about 10 minutes I restarted the HistoryServer and it was behaving normally again.
The cluster is running CDH 5.3 (2.5.0-cdh5.3.0). I've attached the output of jstack from a time this was occurring.