linux-kernel - Re: [PATCH] sched/nohz: Fix NOHZ imbalance by adding options for ILB CPU

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Message-ID: <218b07e0-1cf7-fa8d-4533-d0e8572b3356@gentwo.org>
Date: Fri, 5 Sep 2025 09:45:42 -0700 (PDT)
From: "Christoph Lameter (Ampere)" <cl@...two.org>
To: Frederic Weisbecker <frederic@...nel.org>
cc: Valentin Schneider <vschneid@...hat.com>, 
    Adam Li <adamli@...amperecomputing.com>, mingo@...hat.com, 
    peterz@...radead.org, juri.lelli@...hat.com, vincent.guittot@...aro.org, 
    dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com, 
    mgorman@...e.de, linux-kernel@...r.kernel.org, patches@...erecomputing.com
Subject: Re: [PATCH] sched/nohz: Fix NOHZ imbalance by adding options for
 ILB CPU

On Fri, 5 Sep 2025, Frederic Weisbecker wrote:

> > My wish for the future would be that nohz_full would be the default and
> > that the scheduler does correct load balancing regardless of the cpu being
> > in tick mode or not.
>
> Provided we ever manage to run nohz_full without tradeoffs (offloaded 1Hz tick,
> RCU user/kernel overhead, cputime accounting overhead, use hrtick when
> preemption must be maintained) then yes it would make sense but we are very
> far from that. I'm not even sure this will ever be possible.

We need a genius to have a bright idea on how to handle these tradeoffs to
avoid manual configurations.