We just had a low memory alert on our dAppMon server. We currently run it with -Xms16G and -Xmx16G (and use about 13-14G or so, based on the monitoring dashboard). Our MaxPermSize was 256M.
The alert said "Memory Pool 'Code Cache' low memory detected: 95% of 48Mb used". Description: Low PermGen memory will lead to server crashes even if enough heap memory is available.
Could someone help explain what the 48Mb number comes from, and what issues we will run into increasing the MaxPermGen size up to 384M? I am now getting a server alert that says that this number isn't in the recommended AppMon guidelines, but we run JVMs in house with MaxPermGen up to 500M and above.
the default maximum CodeCache size for a server VM (-server) is 48 MB. You could prevent running in a problem with the code cache by increasing the maximum CodeCache size:
Just for explanation - the Permanent Generation and the CodeCache are both non-heap spaces. The PermSize does not include the CodeCache but is a separate non-heap pool.