linux-kernel - Re: [RFC v5 8/9] sched/deadline: base GRUB reclaiming on the inactive utilization

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Date:   Mon, 8 May 2017 10:06:13 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Luca Abeni <luca.abeni@...tannapisa.it>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@....com>,
        Claudio Scordino <claudio@...dence.eu.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tommaso Cucinotta <tommaso.cucinotta@...up.it>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>
Subject: Re: [RFC v5 8/9] sched/deadline: base GRUB reclaiming on the
 inactive utilization

On Mon, May 08, 2017 at 09:41:08AM +0200, Luca Abeni wrote:
> Hi Peter,
> 
> sorry for the delay; anyway, I am working on fixing the patchset
> according to the comments I received....
> 
> When working on one of your comments, I have a doubt:
> 
> On Mon, 27 Mar 2017 16:26:33 +0200
> Peter Zijlstra <peterz@...radead.org> wrote:
> [...]
> > 
> > 
> > #define BW_SHIFT	20
> > #define BW_UNIT		(1 << BW_SHIFT)
> > 
> > static inline
> > u64 grub_reclaim(u64 delta, struct rq *rq, struct sched_dl_entity
> > *dl_se) {
> > u64 u_inact = rq->dl.this_bw - rq->dl.running_bw; /* Utot -
> > Uact */ u64 u_act;
> [...]
> 
> I think introducing the BW_SHIFT and BW_UNIT defines can be more useful
> in a previous patch (patch 4, where I introduce the "grub_reclaim()"
> function, and use ">> 20" for the first time.

Sure..

> Moreover, the "20" magic number is already used in core.c... Should I
> introduce the defines in sched/sched.h, and change the existing core.c
> code too?

Yes please.

> Is it ok to embed this change in patch 4 (sched/deadline:
> implement GRUB accounting), or should it go in a separate patch?

Whatever you feel is nicest. Currently the thing is fully contained in
the one to_ratio() function (afaict), so the first patch where you make
it escape would be fine.