yulei zhang writes:

quoted

Having a speed throttle is a very primitive knob: it's hard to know what the
correct values are for a user. That's one of the reasons why we've moved away
from that kind of tunable for blkio.

Ultimately, if you want work-conserving behaviour, why not use memory.low?

Thanks. But currently low and high are for cgroup v2 setting, do you
think we'd better
extend the same mechanism to cgroup v1?

The cgroup v1 interface is frozen and in pure maintenance mode -- we're not 
adding new features there and haven't done so for some time.