Date:   Mon, 27 Feb 2023 15:42:36 +0100
From:   Michal =?utf-8?Q?Koutn=C3=BD?= <mkoutny@suse.com>
To:     Vincent Guittot <vincent.guittot@linaro.org>
Cc:     mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
        dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com,
        mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com,
        linux-kernel@vger.kernel.org, parth@linux.ibm.com, tj@kernel.org,
        lizefan.x@bytedance.com, hannes@cmpxchg.org,
        cgroups@vger.kernel.org, corbet@lwn.net, linux-doc@vger.kernel.org,
        qyousef@layalina.io, chris.hyser@oracle.com,
        patrick.bellasi@matbug.net, David.Laight@aculab.com,
        pjt@google.com, pavel@ucw.cz, qperret@google.com,
        tim.c.chen@linux.intel.com, joshdon@google.com, timj@gnu.org,
        kprateek.nayak@amd.com, yu.c.chen@intel.com,
        youssefesmat@chromium.org, joel@joelfernandes.org
Subject: Re: [PATCH v12 6/8] sched/fair: Add sched group latency support
Message-ID: <20230227144236.z6zbgsaohlz6sl7o@blackpad>
References: <20230224093454.956298-1-vincent.guittot@linaro.org>
 <20230224093454.956298-7-vincent.guittot@linaro.org>
 <20230224192919.d4fcde3dwh7betvm@blackpad>
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On Mon, Feb 27, 2023 at 02:44:22PM +0100, Vincent Guittot <vincent.guittot@linaro.org> wrote:
> Regarding the current use of latency nice to set a latency offset, the
> problem doesn't appear because latency offset applies between entities
> at the same level as you mentioned above

Splendid, it turned out that way (latency nice analogous to bandwidth
nice).

> Does  my explanation above make sense to you ?

Yes, thank you.

Thus, I'd like to propose avoiding the use of "limit" in this context and
stress the horizontal scope. For example:

> +     This interface file allows reading and setting latency using the
> +     same values used by sched_setattr(2). The latency_nice of a group is
> +     used to limit the impact of the latency_nice of a task outside the
> +     group.

+     This interface file allows reading and setting latency using the
+     same values used by sched_setattr(2). The latency_nice of a group is
+     used to modify group members' latency with respect to sibling groups.

Regards,
Michal

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