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

From: Alexander Duyck
Date: Wed Sep 26 2018 - 12:19:10 EST

On 9/26/2018 8:41 AM, Dave Hansen wrote:
On 09/26/2018 08:24 AM, Alexander Duyck wrote:
With no options it works just like slub_debug and enables all
available options. So in our case it is a NOP since we wanted the
debugging enabled by default.

Yeah, but slub_debug is different.

First, nobody uses the slub_debug=- option because *that* is only used
when you have SLUB_DEBUG=y *and* CONFIG_SLUB_DEBUG_ON=y, which not even
Fedora does.

slub_debug is *primarily* for *adding* debug features. For this, we
need to turn them off.

It sounds like following slub_debug was a bad idea, especially following
its semantics too closely when it doesn't make sense.

I actually like the idea of using slub_debug style semantics. It makes sense when you start thinking about future features being added. Then we might actually have scenarios where vm_debug=P will make sense, but for right now it is probably not going to be used. Basically this all makes room for future expansion. It is just ugly to read right now while we only have one feature controlled by this bit.