Re: Re: [PATCH 01/15] sched/fair: Add avg_vruntime

[Abel Wu]

On 10/11/23 3:30 PM, Peter Zijlstra Wrote:
> On Wed, Oct 11, 2023 at 12:15:28PM +0800, Abel Wu wrote:
> > On 5/31/23 7:58 PM, Peter Zijlstra wrote:
> > > +/*
> > > + * Compute virtual time from the per-task service numbers:
> > > + *
> > > + * Fair schedulers conserve lag:
> > > + *
> > > + *   \Sum lag_i = 0
> > > + *
> > > + * Where lag_i is given by:
> > > + *
> > > + *   lag_i = S - s_i = w_i * (V - v_i)
> >
> > Since the ideal service time S is task-specific, should this be:
> >
> > 	lag_i = S_i - s_i = w_i * (V - v_i)
>
> It is not, S is the same for all tasks. Remember, the base form is a
> differential equation and all tasks progress at the same time at dt/w_i
> while S progresses at dt/W.

IIUC it's V progresses at dt/W and is same for all tasks, not S which is
measured in real time (V*w_i).