Application Servers Maximum Memory Limit

Question

How much memory can a server (Jboss, Tomcat etc...) use? For example if the server has 128gb memory, can it use at least 100gb of it? I'm using these parameters for my local:

-Xms512m -Xmx1024m -XX:PermSize=256m -XX:MaxPermSize=512

Can these parameters configured for usage of 100gb?

Answer 1

We use this to run a 24GB 64-bit JVM with sub-second GC pauses while serving 100+ page requests per second:

-Xms24g -Xmx24g -XX:MaxPermSize=256m -XX:NewRatio=4 -XX:SurvivorRatio=8    
-XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:+DisableExplicitGC  
-XX:+UseCMSInitiatingOccupancyOnly -XX:+CMSClassUnloadingEnabled  
-XX:+CMSScavengeBeforeRemark -XX:CMSInitiatingOccupancyFraction=68

There shouldn't be any reason you can't specify 100GB if you server has the memory. Since we're using under 32GB we also use -XX:+UseCompressedOops to reduce the overhead of 64-bit addressing. Additionally we use -XX:+UseLargePages for better performance, however you have to enable large page support for your OS first.