linux-kernel - Re: [PATCH RESEND 0/3] Represent cluster topology and enable load balance between clusters

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Message-ID: <20211005075001.GJ4323@worktop.programming.kicks-ass.net>
Date:   Tue, 5 Oct 2021 09:50:01 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Barry Song <21cnbao@...il.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Ben Segall <bsegall@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guodong Xu <guodong.xu@...aro.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Jonathan Cameron <jonathan.cameron@...wei.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        "Cc: Len Brown" <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        LAK <linux-arm-kernel@...ts.infradead.org>,
        Linuxarm <linuxarm@...wei.com>,
        Mark Rutland <mark.rutland@....com>,
        Mel Gorman <mgorman@...e.de>, msys.mizuma@...il.com,
        "Zengtao (B)" <prime.zeng@...ilicon.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Steven Rostedt <rostedt@...dmis.org>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Sudeep Holla <sudeep.holla@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Will Deacon <will@...nel.org>, x86 <x86@...nel.org>,
        yangyicong <yangyicong@...wei.com>
Subject: Re: [PATCH RESEND 0/3] Represent cluster topology and enable load
 balance between clusters

On Fri, Oct 01, 2021 at 04:22:46PM -0700, Tim Chen wrote:
> On Fri, 2021-10-01 at 16:57 +0200, Peter Zijlstra wrote:

> > The one questino I have is, do we want default y?
> 
> I also agree that default y is preferable.

I'll change at least the x86 one to:

	default y
	depends on SMP

> > The one nit I have is the Kconfig text, I'm not really sure that's
> > clarifying what a cluster is.
> 
> Do you have a preference of a different name other than cluster?
> Or simply better documentation on what a cluster is for ARM64
> and x86 in Kconfig?

Yes, better wording as to what a cluster is. Currently the x86 and arm64
ones actually differ:

x86:
	help
	 Cluster scheduler support improves the CPU scheduler's decision
	 making when dealing with machines that have clusters of CPUs
	 sharing L2 cache. If unsure say N here.

arm64:
	help
	  Cluster scheduler support improves the CPU scheduler's decision
	  making when dealing with machines that have clusters(sharing internal
	  bus or sharing LLC cache tag). If unsure say N here.


(also, all this stuff being replicated across arch/*/Kconfig seems
unfortunate)