I have some dm-crypt’ed partitions. And when I copy files between those partiions, I get major blocking going on especially if it involves the system’s encrypted root partition - the terminal becomes unresponsive, things like that. But it affects any partition involved in the i/o operation in a blocking fashion. From top it’s clear that kcryptd goes crazy on the CPU, which is expected. What is not expected is it blocking the system when anything has to do with UNIMPORTANT disk operations on the involved disks.
Setting nice -n N before rsync only lowers the nicety level of the rsync, not the kcryptd (kcryptd continues at high priority, hogging up CPU).
Question 1) Is there a way to lower kcryptd’s priority?
Question 2) Is there a way to lower kcryptd’s priority only for specific file copy/move tasks? (because it IS nice when you can use your encrypted drives with high priority for everything that has to do with running the system)