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

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Message-ID: <f5648747-642f-763e-80b9-24fb203c85e9@intel.com>
Date:   Wed, 26 Sep 2018 08:36:47 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Michal Hocko <mhocko@...nel.org>,
        Alexander Duyck <alexander.h.duyck@...ux.intel.com>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.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 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.

Alex's patch fails at the primary goal, IMNHO because "vm_debug=-" is so
weird.  I'd much rather have "vm_debug=off" (the primary goal) and throw
away the nice-to-have (future-proof fine-grained on/off).

I think we can have both, but I guess the onus is on me to go and add a
strcmp(..., "off"). :)