From: KY Srinivasan <kys@microsoft.com>
To: Andrew Morton <akpm@linux-foundation.org>
CC: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "devel@linuxdriverproject.org" <devel@linuxdriverproject.org>,
        "olaf@aepfle.de" <olaf@aepfle.de>,
        "apw@canonical.com" <apw@canonical.com>,
        "andi@firstfloor.org" <andi@firstfloor.org>
Subject: RE: [PATCH 2/2] Drivers: hv: Add Hyper-V balloon driver
Thread-Topic: [PATCH 2/2] Drivers: hv: Add Hyper-V balloon driver
Thread-Index: AQHNpOUXgnwlsoeYd0afghaYt4KseJexY0uAgAACC0CAAFozAIAAE4mQ
Date: Wed, 10 Oct 2012 02:26:46 +0000
Message-ID: <426367E2313C2449837CD2DE46E7EAF930A33D08@SN2PRD0310MB382.namprd03.prod.outlook.com>
References: <1349654347-18337-1-git-send-email-kys@microsoft.com>
	<1349654386-18378-1-git-send-email-kys@microsoft.com>
	<1349654386-18378-2-git-send-email-kys@microsoft.com>
	<20121009124449.f54bf8cb.akpm@linux-foundation.org>
	<426367E2313C2449837CD2DE46E7EAF930A33CC4@SN2PRD0310MB382.namprd03.prod.outlook.com>
 <20121009181458.e59e7094.akpm@linux-foundation.org>
In-Reply-To: <20121009181458.e59e7094.akpm@linux-foundation.org>
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> -----Original Message-----
> From: Andrew Morton [mailto:akpm@linux-foundation.org]
> Sent: Tuesday, October 09, 2012 9:15 PM
> To: KY Srinivasan
> Cc: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> andi@firstfloor.org
> Subject: Re: [PATCH 2/2] Drivers: hv: Add Hyper-V balloon driver
> 
> On Wed, 10 Oct 2012 00:09:12 +0000 KY Srinivasan <kys@microsoft.com> wrote:
> 
> > > > +		if (!pg) {
> > > > +			*alloc_error = true;
> > > > +			return i * alloc_unit;
> > > > +		}
> > > > +
> > > > +		totalram_pages -= alloc_unit;
> > >
> > > Well, I'd consider totalram_pages to be an mm-private thing which drivers
> > > shouldn't muck with.  Why is this done?
> >
> > By modifying the totalram_pages, the information presented in /proc/meminfo
> > correctly reflects what is currently assigned to the guest (MemTotal).
> 
> eh?  /proc/meminfo:MemTotal tells you the total memory in the machine.
> The only thing which should change it after boot is memory hotplug.
> 
> Modifying it in this manner puts the statistic into a state know as
> "wrong".  And temporarily modifying it in this fashion will cause the
> tremendous amount of initialisation code which relies upon
> totalram_pages for sizing to also enter the "wrong" state.
> 
> Why on earth do balloon drivers do this?  If the amount of memory which
> is consumed by balloons is interesting then it should be exported via a
> standalone metric, not by mucking with totalram_pages.

I see your point. I will get rid of the code that manipulates the totalram_pages.

Regards,

K. Y
 

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