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From:   Josh Don <joshdon@google.com>
Date:   Tue, 28 Mar 2023 16:57:49 -0700
Message-ID: <CABk29Nt-9MufWcyxr8=ghHDj_kUj21vkEw=4X10NpXncxN32uQ@mail.gmail.com>
Subject: Re: [PATCH 04/17] sched/fair: Add avg_vruntime
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     mingo@kernel.org, vincent.guittot@linaro.org,
        linux-kernel@vger.kernel.org, juri.lelli@redhat.com,
        dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com,
        mgorman@suse.de, bristot@redhat.com, corbet@lwn.net,
        qyousef@layalina.io, chris.hyser@oracle.com,
        patrick.bellasi@matbug.net, pjt@google.com, pavel@ucw.cz,
        qperret@google.com, tim.c.chen@linux.intel.com, timj@gnu.org,
        kprateek.nayak@amd.com, yu.c.chen@intel.com,
        youssefesmat@chromium.org, joel@joelfernandes.org, efault@gmx.de
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On Tue, Mar 28, 2023 at 4:06=E2=80=AFAM Peter Zijlstra <peterz@infradead.or=
g> wrote:
[...]
> +/*
> + * Compute virtual time from the per-task service numbers:
> + *
> + * Fair schedulers conserve lag: \Sum lag_i =3D 0
> + *
> + * lag_i =3D S - s_i =3D w_i * (V - v_i)
> + *
> + * \Sum lag_i =3D 0 -> \Sum w_i * (V - v_i) =3D V * \Sum w_i - \Sum w_i =
* v_i =3D 0

Small note: I think it would be helpful to label these symbols
somewhere :) Weight  and vruntime are fairly obvious, but I don't
think 'S' and 'V' are as clear. Are these non-virtual ideal service
time, and average vruntime, respectively?