linux-kernel - Re: [PATCH] mm: add a new command-line kmemcheck value

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Message-ID: <CAOMGZ=HhWoRYMQtqQu73X21eZJAO7fETxOnW=9ZWMkwr9dCPFA@mail.gmail.com>
Date:	Fri, 10 Jan 2014 17:02:42 +0100
From:	Vegard Nossum <vegard.nossum@...il.com>
To:	Xishi Qiu <qiuxishi@...wei.com>
Cc:	Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	Vegard Nossum <vegardno@....uio.no>,
	Pekka Enberg <penberg@...nel.org>,
	Mel Gorman <mgorman@...e.de>, wangnan0@...wei.com,
	"the arch/x86 maintainers" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: add a new command-line kmemcheck value

On 2 January 2014 02:34, Xishi Qiu <qiuxishi@...wei.com> wrote:
> On 2013/12/31 18:12, Vegard Nossum wrote:
>> On 31 December 2013 09:32, Xishi Qiu <qiuxishi@...wei.com> wrote:
>>> Add a new command-line kmemcheck value: kmemcheck=3 (disable the feature),
>>> this is the same effect as CONFIG_KMEMCHECK disabled.
>>> After doing this, we can enable/disable kmemcheck feature in one vmlinux.
>>
>> Could you please explain what exactly the difference is between the
>> existing kmemcheck=0 parameter and the new kmemcheck=3?
>
> kmemcheck=0: enable kmemcheck feature, but don't check the memory.
>         and the OS use only one cpu.(setup_max_cpus = 1)
> kmemcheck=3: disable kmemcheck feature.
>         this is the same effect as CONFIG_KMEMCHECK disabled.
>         OS will use cpus as many as possible.
>

I see. In that case, I think it's better to allow all the CPUs to keep
running while kmemcheck is disabled with kmemcheck=0 boot parameter,
and offline them when/if kmemcheck is reenabled via
/proc/sys/kernel/kmemcheck.


Vegard
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