linux-kernel - Re: [patch 0/4] affine kernel threads to nohz

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Date:   Mon, 20 Apr 2020 18:02:46 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Marcelo Tosatti <mtosatti@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Frederic Weisbecker <fweisbec@...il.com>,
        Chris Friesen <chris.friesen@...driver.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jim Somerville <Jim.Somerville@...driver.com>,
        Christoph Lameter <cl@...ux.com>
Subject: Re: [patch 0/4] affine kernel threads to nohz_full= cpumask (v4)

On Wed, Apr 01, 2020 at 09:10:18AM -0300, Marcelo Tosatti wrote:
> This is a kernel enhancement that configures the cpu affinity of kernel
> threads via kernel boot option nohz_full=.
> 
> When this option is specified, the cpumask is immediately applied upon
> thread launch. This does not affect kernel threads that specify cpu
> and node.
> 
> This allows CPU isolation (that is not allowing certain threads
> to execute on certain CPUs) without using the isolcpus=domain parameter,
> making it possible to enable load balancing on such CPUs
> during runtime (see kernel-parameters.txt).
> 
> Note-1: this is based off on Wind River's patch at
> https://github.com/starlingx-staging/stx-integ/blob/master/kernel/kernel-std/centos/patches/affine-compute-kernel-threads.patch
> 
> Difference being that this patch is limited to modifying
> kernel thread cpumask: Behaviour of other threads can
> be controlled via cgroups or sched_setaffinity.
> 
> Note-2: Wind River's patch was based off Christoph Lameter's patch at
> https://lwn.net/Articles/565932/ with the only difference being
> the kernel parameter changed from kthread to kthread_cpus.
> 
> v2: use isolcpus= subcommand (Thomas Gleixner)
> 
> v3: s/MontaVista/Wind River/ on changelog (Chris Friesen)
>     documentation updates                 (Chris Friesen)
>     undeprecate isolcpus                  (Chris Friesen)
>     general cleanups                      (Frederic Weisbecker)
>     separate cpu_possible_mask kthread
>     mask change                           (Frederic Weisbecker)
> 
> v4: disable idle load balancing for nohz_full=
>     use nohz_full= option for kthread isolation (Frederic Weisbecker)
> 


Thanks for the patches. I'm applying them, I may add a few details
to the changelogs and stuff.