linux-kernel - Re: [PATCH] smp: Add bootcpus parameter to boot subset of CPUs

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Message-ID: <8736204xmu.fsf@nanos.tec.linutronix.de>
Date:   Mon, 26 Oct 2020 20:04:25 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     psodagud@...eaurora.org
Cc:     Elliot Berman <eberman@...eaurora.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Trilok Soni <tsoni@...eaurora.org>,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH] smp: Add bootcpus parameter to boot subset of CPUs

On Mon, Oct 26 2020 at 10:08, psodagud wrote:
> Based on my understanding with maxcpus option provides, maximum no of 
> CPUs are brough up during the device boot up. There is a different case, 
> in which we want to restrict which CPUs to be brough up.

Again: What for? Why?

> On a system with 8 cpus, if we set maxcpus as 3, cpu0, cpu1, and cpu2 
> are brough up during the bootup.  For example, if we want to bring 
> core0, core3 and core4 current maxcpu(as 3) setting would not help us.
> On some platform we want the flexibility on which CPUs to bring up 
> during the device bootup. bootcpus command line is helping to bring 
> specific CPUs and these patches are working downstream.

A lot of patches work downstream by some definition of work. But that
does not make an argument to bring them upstream.

Thanks,

        tglx