The process will run fine all day, then, bam, without warning, it will throw this error. Sometimes seemingly in the middle of doing nothing. It will happen at seemingly random times during the day. I checked to see if anything else was running on the machine, like scheduled backups or something, but found nothing. The machine has enough physical memory (2GB, with about 1GB free for a 3-500MB load), and has sufficient -Xmx specified.

According to our sysadmin, the problem is that the RAM that the kernel uses as a disk cache (apparently all but 8MB) is not freed when the JVM needs to allocate memory, so the JVM process throws an OutOfMemoryError. This could be because Java asks the kernel if enough memory is available before allocating and finds that it is insufficient, resulting in a crash.

I would like to think, however, that Java simply tries to allocate the memory via the kernel, and when the kernel gets such a request, it makes room for the application by throwing our some of the disk cache.

Has anyone else run in to the issue, and if so, what was the error, and how did you solve it? We are currently using jdk1.6.0_20 on SLES 10 SP2 Linux 2.6.16.60-0.42.9-smp in VMWare ESX.