linux-kernel - Re: [PATCH v2 1/2] mm: Move page struct poisoning to CONFIG_DEBUG_VM_PAGE_INIT

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Date:   Thu, 6 Sep 2018 09:09:46 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Alexander Duyck <alexander.duyck@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, alexander.h.duyck@...el.com,
        pavel.tatashin@...rosoft.com, akpm@...ux-foundation.org,
        mingo@...nel.org, kirill.shutemov@...ux.intel.com
Subject: Re: [PATCH v2 1/2] mm: Move page struct poisoning to
 CONFIG_DEBUG_VM_PAGE_INIT_POISON

On 09/06/2018 08:13 AM, Michal Hocko wrote:
>> 	CONFIG_DEBUG_VM_SLOW_AS_HECK
>>
>> under which we can put this an other really slow VM debugging.  Or, we
>> need some kind of boot-time parameter to trigger the extra checking
>> instead of a new CONFIG option.
> I strongly suspect nobody will ever enable such a scary looking config
> TBH. Besides I am not sure what should go under that config option.

OK, so call it CONFIG_DEBUG_VM2, or CONFIG_DEBUG_VM_MORE. :)

What do we put under it?  The things that folks complain about that get
turned on with DEBUG_VM, like this.

> Is this worth a separate config option almost nobody is going to
> enable?
Yes.  We get basically *zero* debug checking from this option.  We want
it available to developers mucking with boot and hotplug, but it's
honestly not worth it for normal users.

Has anyone ever seen a single in-the-wild report from this mechanism?