linux-kernel - Re: [PATCH v5 2/4] mm: Provide kernel parameter to allow disabling page init poisoning

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Message-Id: <20180926153615.90661e27d0713a02651b2282@linux-foundation.org>
Date:   Wed, 26 Sep 2018 15:36:15 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-nvdimm@...ts.01.org, pavel.tatashin@...rosoft.com,
        dave.jiang@...el.com, jglisse@...hat.com, rppt@...ux.vnet.ibm.com,
        dan.j.williams@...el.com, logang@...tatee.com, mingo@...nel.org,
        kirill.shutemov@...ux.intel.com
Subject: Re: [PATCH v5 2/4] mm: Provide kernel parameter to allow disabling
 page init poisoning

On Wed, 26 Sep 2018 08:36:47 -0700 Dave Hansen <dave.hansen@...el.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.