linux-kernel - Re: [PATCH] affine kernel threads to specified cpumask

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Message-ID: <87imiuq0cg.fsf@nanos.tec.linutronix.de>
Date:   Mon, 23 Mar 2020 21:31:59 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Chris Friesen <chris.friesen@...driver.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        linux-kernel@...r.kernel.org
Cc:     Christoph Lameter <cl@...ux.com>, Vu Tran <vu.tran@...driver.com>,
        Jim Somerville <Jim.Somerville@...driver.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] affine kernel threads to specified cpumask

Chris,

Chris Friesen <chris.friesen@...driver.com> writes:
> On 3/23/2020 10:22 AM, Thomas Gleixner wrote:
>> Marcelo Tosatti <mtosatti@...hat.com> writes:
>>> This allows CPU isolation (that is not allowing certain threads
>>> to execute on certain CPUs) without using the isolcpus= parameter,
>>> making it possible to enable load balancing on such CPUs
>>> during runtime.
>> 
>> I'm surely missing some background information, but that sentence does
>> not make any sense to me.
>
> The idea is to affine general kernel threads to specific "housekeeping" 
> CPUs, while still allowing load balancing of tasks.
>
> The isolcpus= boot parameter would prevent kernel threads from running 
> on the isolated CPUs, but it disables load balancing on the isolated CPUs.

So why can't we just have a isolcpus mode which allows that instead of
adding more command line options which are slightly different?

We just added some magic for managed interrupts to isolcpus, which is
surely interesting for your scenario as well...

Thanks,

        tglx