linux-kernel - Re: [PATCH mm-unstable] lib/Kconfig.debug: do not enable DEBUG

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Message-ID: <Y9AIj5OLmPAH8cXF@hyeyoo>
Date:   Wed, 25 Jan 2023 01:34:23 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     Christoph Lameter <cl@...two.de>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Ingo Molnar <mingo@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH mm-unstable] lib/Kconfig.debug: do not enable
 DEBUG_PREEMPT by default

On Mon, Jan 23, 2023 at 12:05:00PM +0100, Christoph Lameter wrote:
> On Sat, 21 Jan 2023, Hyeonggon Yoo wrote:
> 
> > Whew, I still get confused about who to Cc, thanks for adding them.
> > and I also didn't include the percpu memory allocator maintainers, who may
> > have opinion. let's add them too.
> 
> Well looks ok to me.

Thanks for looking at!

> However, I thought most distro kernels disable PREEMPT anyways for
> performance reasons? So DEBUG_PREEMPT should be off as well. I guess that
> is why this has not been an issue so far.

It depends on PREEMPTION, and PREEMPT_DYNAMIC ("Preemption behaviour defined on boot")
selects PREEMPTION even if I end up using PREEMPT_VOLUNTARY.

Not so many distros use DEBUG_PREEMPT, but I am occationally hit by this
because debian and fedora enabled it :)