Java : Get heap dump without jmap or without hanging the application

Question

In few circumstance, our application is using around 12 GB of memory. We tried to get the heap dump using jmap utility. Since the application is using some GB of memory it c

Answer 1

You can use GDB to get the heap dump without running jmap on the target VM however this will still hang the application for the amount of time required to write the heap dump to disk. Assuming a disk speed of 100MB/s (a basic mirrored array or single disk) this is still 2 minutes of downtime. http://blogs.atlassian.com/2013/03/so-you-want-your-jvms-heap/

The only true way to avoid stopping the JVM is transactional memory and a kernel that takes advantage of it to provide a process snapshot facility. This is one of the dreams of the proponents of STM but it's not available yet. VMWare's hot-migration comes close but depends on your allocation rate not exceeding network bandwidth and it doesn't save snapshots. Petition them to add it for you, it'd be a neat feature.