I have a computer with 3 Intel Optane drives and iotop shows that sequential write to each one separately achieves ~2.2 GB/sec. I suppose that simultaneous writing on all three would result in ~6.6 GB/sec. But in reality I got only 3 GB/sec if I try to write to two disks simultaneoulsy and the same 3 GB/sec even if I use all three. What can be the root of the problem?
Kernel is 4.20.3, Ubuntu, Processor Core i7 7800X. Top shows high kernel load but only for quarter of the CPUs.
And here is what /proc/interrupts shows: http://paste.ubuntu.com/p/h4PC9WWVSv/