linux-kernel - Re: [PATCH v2] mm/hotplug, x86: Disable ARCH_MEMORY

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Date:	Thu, 25 Jul 2013 16:36:03 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, x86@...nel.org, dave@...1.net,
	kosaki.motohiro@...il.com, isimatu.yasuaki@...fujitsu.com,
	tangchen@...fujitsu.com, vasilis.liaskovitis@...fitbricks.com
Subject: Re: [PATCH v2] mm/hotplug, x86: Disable ARCH_MEMORY_PROBE by default

On Thu, 2013-07-25 at 23:38 +0200, Ingo Molnar wrote:
> * Toshi Kani <toshi.kani@...com> wrote:
> 
> > > You claimed that the only purpose of this on x86 was 
> > > that testing was done on non-hotplug systems, using 
> > > this interface. Non-hotplug systems have e820 maps.
> > 
> > Right.  Sorry, I first thought that the interface needed 
> > to work as defined, i.e. detect a new memory.  But for 
> > the test purpose on non-hotplug systems, that is not 
> > necessary.  So, I agree that we can check e820.
> > 
> > I summarized two options in the email below.
> > https://lkml.org/lkml/2013/7/23/602
> > 
> > Option 1) adds a check with e820.  Option 2) deprecates 
> > the interface by removing the config option from x86 
> > Kconfig.  I was thinking that we could evaluate two 
> > options after this patch gets in.  Does it make sense?
> 
> Yeah.
> 
> That having said, if the e820 check is too difficult to 
> pull off straight away, I also don't mind keeping it as-is 
> if it's useful for testing. Just make sure you document it 
> as "you need to be careful with this" (beyond it being a 
> root-only interface to begin with).

Sounds good.  I will keep it as-is for now, and add more clarification
to the document.  I will send an updated patch shortly.

I will make sure to come back after this patch gets in and we get more
info about users.

Thanks,
-Toshi

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