linux-kernel - Re: [RFC PATCH 08/12] mm: use mirrorable to switch allocate mirrored memory

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Message-ID: <55709BEA.8030903@intel.com>
Date:	Thu, 04 Jun 2015 11:41:46 -0700
From:	Dave Hansen <dave.hansen@...el.com>
To:	Xishi Qiu <qiuxishi@...wei.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	nao.horiguchi@...il.com, Yinghai Lu <yinghai@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>, mingo@...e.hu,
	Xiexiuqi <xiexiuqi@...wei.com>,
	Hanjun Guo <guohanjun@...wei.com>,
	"Luck, Tony" <tony.luck@...el.com>
CC:	Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 08/12] mm: use mirrorable to switch allocate mirrored
 memory

On 06/04/2015 06:02 AM, Xishi Qiu wrote:
> Add a new interface in path /proc/sys/vm/mirrorable. When set to 1, it means
> we should allocate mirrored memory for both user and kernel processes.

That's a pretty dangerously short name. :)

How would this end up getting used?  It seems like it would be dangerous
to use once userspace was very far along.  So would the kernel set it to
1 and then let (early??) userspace set it back to 0?  That would let
important userspace like /bin/init get mirrored memory without having to
actually change much in userspace.

This definitely needs some good documentation.

Also, if it's insane to turn it back *on*, maybe it should be a one-way
trip to turn off.
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