linux-kernel - Re: [PATCH 4/9] sched: Move SCHED

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Date:   Wed, 07 Apr 2021 13:57:22 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...nel.org, mgorman@...e.de, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, bristot@...hat.com,
        joshdon@...gle.com, linux-kernel@...r.kernel.org, greg@...ah.com
Subject: Re: [PATCH 4/9] sched: Move SCHED_DEBUG to debugfs

On 07/04/21 14:26, Peter Zijlstra wrote:
> On Wed, Apr 07, 2021 at 11:46:43AM +0100, Valentin Schneider wrote:
>> I can't find the threads in a hurry, but ISTR justifications for keeping
>> this around were:
>> - Most distros have CONFIG_SCHED_DEBUG=y because knobs and ponies
>> - Topology debug prints are "too verbose"
>
> ^^ that mostly.
>
>> - NUMA distance matrix processing gets slower
>>
>> If we make it so distros stop / don't need to select CONFIG_SCHED_DEBUG,
>
> We're not there yet, I think :-(
>

Yeah, I know, a man can dream... At least now I can make use of
CMDLINE_EXTEND on arm64.

>> then I don't think the above really stands anymore (also, sched_init_numa()
>> now has the same complexity regardless of sched_debug), and we could keep
>> everything under CONFIG_SCHED_DEBUG.
>
> But yes, the reason this knob exists is ebcause I too frequently forget
> to add the boot time knob, so I added this one to enable it at runtime
> and then I get topology prints when I hotplug cycle a cpu.