I have two java applications (openhab2 and eq3 occu) on an ubuntu 18.04 machine that are doing some background activity. I would expect this to happen in memory. But for both applications iotop is showing a disk write operation approx. every second.
- I'm running laptop mode tools which set the filesystem parameters and hdparm to spin down the disk even if there are changes to files and write them later.
- I moved all log files to a folder in tmpfs.
- I turned off swap, as there is plenty of RAM in the machine.
- With /proc/#pid#/fs I can't see any open files which would be written.
- find -mmin 1 is not showing any updated files.
As it happens for both applications the same way, I suspect that the java jvm is doing something on the disc directly.
Behavior is the same whether I use openjdk1.8 or oracle java 10. I tried to use G1GC. That reduces garbage collection efforts but doesn't let the disc sleep, either.
Could anyone give me a hint, what I could do to find out what is happening here?
Thanks a lot!
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