Date:   Wed, 25 Jan 2023 01:34:23 +0900
From:   Hyeonggon Yoo <42.hyeyoo@gmail.com>
To:     Christoph Lameter <cl@gentwo.de>
Cc:     Vlastimil Babka <vbabka@suse.cz>,
        Andrew Morton <akpm@linux-foundation.org>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Ingo Molnar <mingo@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Shakeel Butt <shakeelb@google.com>,
        Muchun Song <muchun.song@linux.dev>,
        Matthew Wilcox <willy@infradead.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Valentin Schneider <vschneid@redhat.com>,
        Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH mm-unstable] lib/Kconfig.debug: do not enable
 DEBUG_PREEMPT by default
Message-ID: <Y9AIj5OLmPAH8cXF@hyeyoo>
References: <20230121033942.350387-1-42.hyeyoo@gmail.com>
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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 :)