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Date:   Wed, 26 Sep 2018 09:38:31 +0200
From:   Michal Hocko <mhocko@kernel.org>
To:     Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc:     linux-mm@kvack.org, akpm@linux-foundation.org,
        linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org,
        pavel.tatashin@microsoft.com, dave.jiang@intel.com,
        dave.hansen@intel.com, jglisse@redhat.com, rppt@linux.vnet.ibm.com,
        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
Message-ID: <20180926073831.GC6278@dhcp22.suse.cz>
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 <20180925201921.3576.84239.stgit@localhost.localdomain>
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On Tue 25-09-18 13:20:12, Alexander Duyck wrote:
[...]
> +	vm_debug[=options]	[KNL] Available with CONFIG_DEBUG_VM=y.
> +			May slow down system boot speed, especially when
> +			enabled on systems with a large amount of memory.
> +			All options are enabled by default, and this
> +			interface is meant to allow for selectively
> +			enabling or disabling specific virtual memory
> +			debugging features.
> +
> +			Available options are:
> +			  P	Enable page structure init time poisoning
> +			  -	Disable all of the above options

I agree with Dave that this is confusing as hell. So what does vm_debug
(without any options means). I assume it's NOP and all debugging is
enabled and that is the default. What if I want to disable _only_ the
page struct poisoning. The weird lookcing `-' will disable all other
options that we might gather in the future.

Why cannot you simply go with [no]vm_page_poison[=on/off]?
-- 
Michal Hocko
SUSE Labs