linux-kernel - RE: [PATCH 1/2] mm: Export vm_committed

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Message-ID: <426367E2313C2449837CD2DE46E7EAF930E0D0CC@CH1PRD0310MB381.namprd03.prod.outlook.com>
Date:	Thu, 8 Nov 2012 22:01:33 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	David Rientjes <rientjes@...gle.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"andi@...stfloor.org" <andi@...stfloor.org>,
	"apw@...onical.com" <apw@...onical.com>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Hiroyuki Kamezawa <kamezawa.hiroyuki@...il.com>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Ying Han <yinghan@...gle.com>
Subject: RE: [PATCH 1/2] mm: Export vm_committed_as



> -----Original Message-----
> From: David Rientjes [mailto:rientjes@...gle.com]
> Sent: Monday, November 05, 2012 5:33 PM
> To: KY Srinivasan
> Cc: Andrew Morton; Greg KH; olaf@...fle.de; linux-kernel@...r.kernel.org;
> andi@...stfloor.org; apw@...onical.com; devel@...uxdriverproject.org; linux-
> mm@...ck.org; Hiroyuki Kamezawa; Michal Hocko; Johannes Weiner; Ying Han
> Subject: RE: [PATCH 1/2] mm: Export vm_committed_as
> 
> On Mon, 5 Nov 2012, KY Srinivasan wrote:
> 
> > The Hyper-V host has a policy engine for managing available physical memory
> across
> > competing virtual machines. This policy decision is based on a number of
> parameters
> > including the memory pressure reported by the guest. Currently, the pressure
> calculation is
> > based on the memory commitment made by the guest. From what I can tell,
> the ratio of
> > currently allocated physical memory to the current memory commitment made
> by the guest
> > (vm_committed_as) is used as one of the parameters in making the memory
> balancing decision on
> > the host. This is what Windows guests report to the host. So, I need some
> measure of memory
> > commitments made by the Linux guest. This is the reason I want export
> vm_committed_as.
> >
> 
> I don't think you should export the symbol itself to modules but rather a
> helper function that returns s64 that just wraps
> percpu_counter_read_positive() which your driver could use instead.
> 
> (And why percpu_counter_read_positive() returns a signed type is a
> mystery.)

Yes, this makes sense. I just want to access (read) this metric. Andrew, if you are willing to
take this patch, I could send one.

Regards,

K. Y
 

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