linux-kernel - Re: [PATCH v2 02/12] sched/deadline: Less agressive dl

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Message-ID: <CAMuHMdVPR7Q7pvn+QqGcq2pJ00apDgUcaCmAgq6nnM1uHySMcw@mail.gmail.com>
Date: Wed, 30 Jul 2025 12:05:05 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Juri Lelli <juri.lelli@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>, mingo@...hat.com, vincent.guittot@...aro.org, 
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com, 
	mgorman@...e.de, vschneid@...hat.com, clm@...a.com, 
	linux-kernel@...r.kernel.org, linux-m68k <linux-m68k@...ts.linux-m68k.org>
Subject: Re: [PATCH v2 02/12] sched/deadline: Less agressive dl_server handling

Hi Juri,

On Wed, 30 Jul 2025 at 11:46, Juri Lelli <juri.lelli@...hat.com> wrote:
> On 30/07/25 11:34, Geert Uytterhoeven wrote:
> Apologies for interjecting.

No apologies needed, much appreciated!

> > On Wed, 2 Jul 2025 at 14:19, Peter Zijlstra <peterz@...radead.org> wrote:
> > > Chris reported that commit 5f6bd380c7bd ("sched/rt: Remove default
> > > bandwidth control") caused a significant dip in his favourite
> > > benchmark of the day. Simply disabling dl_server cured things.
> > >
> > > His workload hammers the 0->1, 1->0 transitions, and the
> > > dl_server_{start,stop}() overhead kills it -- fairly obviously a bad
> > > idea in hind sight and all that.
> > >
> > > Change things around to only disable the dl_server when there has not
> > > been a fair task around for a whole period. Since the default period
> > > is 1 second, this ensures the benchmark never trips this, overhead
> > > gone.
> > >
> > > Fixes: 557a6bfc662c ("sched/fair: Add trivial fair server")
> > > Reported-by: Chris Mason <clm@...a.com>
> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > > Link: https://lkml.kernel.org/r/20250520101727.507378961@infradead.org
> >
> > Thanks for your patch, which is now commit cccb45d7c4295bbf
> > ("sched/deadline: Less agressive dl_server handling") upstream.
> >
> > This commit causes
> >
> >     sched: DL replenish lagged too much
> >
> > to be printed after full user-space (Debian) start-up on m68k
> > (atari_defconfig running on ARAnyM).  Reverting this commit and fixing
> > the small conflict gets rid of the message.
>
> Does
> https://lore.kernel.org/lkml/20250615131129.954975-1-kuyo.chang@mediatek.com/
> help already (w/o the revert)?

Thanks, it does!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds