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

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Message-ID: <557113CF.6000905@huawei.com>
Date:	Fri, 5 Jun 2015 11:13:19 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Dave Hansen <dave.hansen@...el.com>
CC:	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>, 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 2015/6/5 2:41, Dave Hansen wrote:

> 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. :)
> 

Hi Dave,

Thanks for your comment. I'm not sure whether we should add this interface
for user processes. However some important userspace(e.g. /bin/init, key
business like datebase) may be want mirrored memory to improve reliability.

If we want this interface, I think the code need more change.

Thanks,
Xishi Qiu

> 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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