ionice -c2 -n7 <PID> on an I/O-intensive process (VirtualBox VM) and checking the result with
ionice -p <PID> it shows
best-effort: prio 7 which is expected.
But when monitoring the overall disk I/O of all processes via
iotop it shows in
PRIO column a value of
be/4 for that process, which I assume means best-effort and level (priority) 4, which is average priority and not expected.
Can somebody comment why there's a difference between what ionice and what iotop displays? And is there another way to verify the actual I/O priority of a given process other then with
ionice -p ?
From what I understood, there's
/proc/<pid>/io but it only displays bytes/characters read and written, but not the priority, cf. Know which process does I/O without iotop
Also How do I view the IO priority of a process? only lists
For completeness sake, this is on RHEL 6.7 with iotop 0.3.2, and the scheduler is the default CFQ.