Re: [RFC 6/6] sched/fair: Add sched group latency support

[Tejun Heo]

Hello,

On Tue, Mar 22, 2022 at 05:10:36PM +0100, Vincent Guittot wrote:
> latency_nice is quite similar to nice. The nice latency is used as an
> index to get a latency weight in the range [-1024:1024].  latency_nice
> is in the range [-20:19] and latency_prio shifts it in the range
> [0:40] . This index is then used to get the latency weight similar to
> how the nice prio is used to get a weight. That being said, the
> latency should probably reflect the latency_weight instead of the
> latency_prio in order to be aligned with the weight and weight.nice
> fields of cgroups.
> 
> As described in patch 5 commit message, the weight is then used to
> compute a relative offset to check whether the waking task can preempt
> the current running task.

So, what I'm trying to say is if it is actually a weight, just use weight
values instead of arbitrary mapped nice values. Nobody can tell how the
latency nice value of -2 compares against, say, 3. If you can define it
clearly in terms of weights (or something else clearly describable), it'd be
a lot better.

Thanks.

-- 
tejun