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Date:   Wed, 26 Sep 2018 15:36:15 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     Michal Hocko <mhocko@kernel.org>,
        Alexander Duyck <alexander.h.duyck@linux.intel.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
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        dan.j.williams@intel.com, logang@deltatee.com, mingo@kernel.org,
        kirill.shutemov@linux.intel.com
Subject: Re: [PATCH v5 2/4] mm: Provide kernel parameter to allow disabling
 page init poisoning
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On Wed, 26 Sep 2018 08:36:47 -0700 Dave Hansen <dave.hansen@intel.com> wrote:

> On 09/26/2018 12:38 AM, Michal Hocko wrote:
> > Why cannot you simply go with [no]vm_page_poison[=on/off]?
> 
> I was trying to look to the future a bit, if we end up with five or six
> more other options we want to allow folks to enable/disable.  I don't
> want to end up in a situation where we have a bunch of different knobs
> to turn all this stuff off at runtime.
> 
> I'd really like to have one stop shopping so that folks who have a
> system that's behaving well and don't need any debugging can get some of
> their performance back.
> 
> But, the *primary* thing we want here is a nice, quick way to turn as
> much debugging off as we can.  A nice-to-have is a future-proof,
> slub-style option that will centralize things.

Yup.  DEBUG_VM just covers too much stuff nowadays.  A general way to
make these thing more fine-grained and without requiring a rebuild
would be great.

And I expect that quite a few of the debug features could be
enabled/disabled after bootup as well, so a /proc knob is probably in
our future.  Any infrastructure which is added to support a new
kernel-command-line option should be designed with that in mind.