New oleg firmware version

[wpte]

My guess that is is due to our old bdi(backing device interface) kernel subsystem. Modern kernels has per-device bdi, our still use single kthread. Hope, I able to backport per-device bdi in futer, but it requires a lot of time & efforts.

I really think it was the debugging version that gave me the extra load.
yesterday I upgraded the modules, including the firmware and it seems to be pretty much the same load as it used to be again:

The graph displays an entire week again.
So EXT4 means (almost) no extra load