Re: [Resend PATCH] psi : calc cfs task memstall time more precisely

[Peter Zijlstra]

On Wed, Nov 10, 2021 at 09:37:00AM +0800, Zhaoyang Huang wrote:
> On Tue, Nov 9, 2021 at 10:56 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> >
> > On Tue, Nov 02, 2021 at 03:47:33PM -0400, Johannes Weiner wrote:
> > > CC peterz as well for rt and timekeeping magic
> > >
> > > On Fri, Oct 15, 2021 at 02:16:52PM +0800, Huangzhaoyang wrote:
> > > > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> > > >
> > > > In an EAS enabled system, there are two scenarios discordant to current design,
> > > >
> > > > 1. workload used to be heavy uneven among cores for sake of scheduler policy.
> > > > RT task usually preempts CFS task in little core.
> > > > 2. CFS task's memstall time is counted as simple as exit - entry so far, which
> > > > ignore the preempted time by RT, DL and Irqs.
> >
> > It ignores preemption full-stop. I don't see why RT/IRQ should be
> > special cased here.
> As Johannes comments, what we are trying to solve is mainly the
> preempted time of the CFS task by RT/IRQ, NOT the RT/IRQ themselves.
> Could you please catch up the recent reply of Dietmar, which maybe
> provide more information.

In that case NAK.