Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 24 Jul 2023 22:11:50 +0100
From:   Qais Yousef <qyousef@layalina.io>
To:     Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc:     Vincent Guittot <vincent.guittot@linaro.org>,
        Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] sched/fair: Fix impossible migrate_util scenario in
 load balance
Message-ID: <20230724211150.lc5dlxlbewxwr5rb@airbuntu>
References: <20230718161829.ws3vn3ufnod6kpxh@airbuntu>
 <CAKfTPtA55NemHq0tZPuiEN=c3DRZWD-7jf7ZrKdHE9y9b_szZg@mail.gmail.com>
 <20230718172522.s4gcfx3ppljwbks7@airbuntu>
 <CAKfTPtA6s82qXWOSdd6eNu__z_HZe9U_F0+RcBJj=PVKT7go7A@mail.gmail.com>
 <20230721105711.nzunqdtdaevmrgyg@airbuntu>
 <ZLqNmpQdiTC2fio5@vingu-book>
 <20230721220430.qv6eqo4dosfrsilo@airbuntu>
 <c31e5667-19b1-33a4-d1f1-a88907e239d3@arm.com>
 <20230724161038.nreywdwayiq2ypty@airbuntu>
 <1e675286-b4b8-5abd-dd4c-3f2ffdaf12c1@arm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <1e675286-b4b8-5abd-dd4c-3f2ffdaf12c1@arm.com>
Precedence: bulk

On 07/24/23 19:54, Dietmar Eggemann wrote:
> On 24/07/2023 18:10, Qais Yousef wrote:
> > On 07/24/23 14:58, Dietmar Eggemann wrote:
> >> On 22/07/2023 00:04, Qais Yousef wrote:
> >>> On 07/21/23 15:52, Vincent Guittot wrote:
> >>>> Le vendredi 21 juil. 2023 à 11:57:11 (+0100), Qais Yousef a écrit :
> >>>>> On 07/20/23 14:31, Vincent Guittot wrote:
> 
> [...]
> 
> > So I actually moved everything to a single cluster and this indeed solves the
> > lb() issue. But then when I tried to look at DT mainline I saw that the DTs
> > still define separate cluster for each uArch, and this got me confused whether
> > I did the right thing or not. And made me wonder whether the fix is to change
> > DT or port Sudeep's/Ionela's patch?
> 
> IMHO, you have to change DT.
> 
> > I did some digging and I think the DT, like the ones in mainline by the look of
> > it, stayed the way it was historically defined.
> 
> This would be a "mistake" for Arm DynamIQ based systems. We use QC RB5
> in our testing and this board schedules only within a MC sched domain (I
> guess it's: arch/arm64/boot/dts/qcom/qrb5165-rb5.dts -> sm8250.dtsi)

I did find some qcom platforms that define a single cluster after I sent my
email. Not sure if the ones I've looked at were having wrong definitions or
not.

Anyway, hope this discussion will enlighten others too ;-)


Cheers

--
Qais Yousef