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Sender: Tejun Heo <htejun@gmail.com>
Date:   Wed, 21 Sep 2022 06:48:43 -1000
From:   Tejun Heo <tj@kernel.org>
To:     Qais Yousef <qais.yousef@arm.com>
Cc:     Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>, mingo@redhat.com,
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Subject: Re: [PATCH v4 6/8] sched/fair: Add sched group latency support
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Hello,

On Wed, Sep 21, 2022 at 05:07:38PM +0100, Qais Yousef wrote:
> Wouldn't cpu.latency.nice be enough? I think the latency_offset is
> implementation detail that userspace shouldn't be concerned about.

One option could be just using the same mapping as cpu.weight so that 100
maps to neutral, 10000 maps close to -20, 1 maps close to 19. It isn't great
that the value can't be interpreted in any intuitive way (e.g. a time
duration based interface would be a lot easier to grok even if it still is
best effort) but if that's what the per-task interface is gonna be, it'd be
best to keep cgroup interface in line.

As for whether a single value would fit the bill, it's again something which
should be answered for both task and cgroup based interface at the same
time. That said, my not-too-throught-through opinion is that a single value
for per-task / per-cgroup interface + system level knobs to fine tune how
that actually applies is likely enough and probably better than exposing
exposing a host of internal details to applications directly.

Thanks.

-- 
tejun