Re: [PATCH 1/2] block/mq-deadline: disable I/O priority when prio_aging_expire is zero

On 8/20/26 7:06 PM, yebin wrote:
> On 2026/8/20 23:31, Bart Van Assche wrote:
>> On 8/19/26 7:12 PM, Ye Bin wrote:
>>> Since the mq-deadline scheduler introduced support for I/O priorities,
>>> if a process does not have an I/O priority configured, it becomes bound
>>> to the process's scheduling priority.
>>
>> How can this happen? The scheduling priority (sched_setparam()) and I/O
>> priority (ioprio_set()) are independent as far as I know.
>>
> Yes, I thought so at first. However, after checking the historical records,
> I found that the IO priority was set based on the task scheduling class 
> when
> the IO priority was not configured. This was introduced by the f7eda402878b
> ("block: Return effective IO priority from get_current_ioprio()") and
> a78418e6a04c ("block: Always initialize bio IO priority on submit") 
> commits.
Thank you for having looked this up. Despite this, it should be possible
to assign the same I/O priority to all I/O from all processes by
configuring the io.prio.class cgroup attribute for all cgroups, isn't
it? See also Documentation/admin-guide/cgroup-v2.rst.

Bart.