> From: Washburn, Brian J [IT] [mailto:brian.j.washb...@sprint.com] > Subject: RE: Effect of Heap Size on Performance? > > Also remember to statically size heap regions manually if you > can as that will always improve GC performance
Don't bet on that; doing so may force excessive minor GCs if you guessed wrong. It is a good idea to set -Xms the same as -Xmx, but unless you have thoroughly analyzed your specific heap usage, don't set the individual generation sizes. Even a minor application change could upset any balance you've achieved. > -XX:+UseConcMarkSweepGC Be aware that although the above will virtually eliminate application pause time for a major GC, it will also *reduce* throughput slightly, since it's not as efficient a collection mechanism. Note that if you have any code that calls System.gc() directly (generally a bad idea), you will also want this: -XX:+ExplicitGCInvokesConcurrent Also note that using the concurrent collector disables adaptive size policy, making it impossible for the JVM to appropriately respond to changing conditions. > -XX:+UseParNewGC Not necessary with the concurrent collector in 1.6 JVMs, since the CMS collector now defaults to parallel on for the young generation. > -XX:+UseCMSInitiatingOccupancyOnly > -XX:CMSInitiatingOccupancyFraction=85 These have the risk of not collecting frequently enough, with the possible end result of having to do a full-pause collection. Use these with caution, only after thorough testing. - Chuck THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY MATERIAL and is thus for use only by the intended recipient. If you received this in error, please contact the sender and delete the e-mail and its attachments from all computers. --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
