From: KY Srinivasan <kys@microsoft.com>
To: David Rientjes <rientjes@google.com>
CC: Andrew Morton <akpm@linux-foundation.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        "olaf@aepfle.de" <olaf@aepfle.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "andi@firstfloor.org" <andi@firstfloor.org>,
        "apw@canonical.com" <apw@canonical.com>,
        "devel@linuxdriverproject.org" <devel@linuxdriverproject.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>,
        Michal Hocko <mhocko@suse.cz>, Johannes Weiner <hannes@cmpxchg.org>,
        Ying Han <yinghan@google.com>
Subject: RE: [PATCH 1/2] mm: Export vm_committed_as
Thread-Topic: [PATCH 1/2] mm: Export vm_committed_as
Thread-Index: AQHNpOUVxeGuP2ksmkqoWwiw1ukrt5eukjYAgAAumACAAKkDgIAB+liAgCbqv6CAA6TlAIAAA/OAgAAJiQCABK2ZcA==
Date: Thu, 8 Nov 2012 22:01:33 +0000
Message-ID: <426367E2313C2449837CD2DE46E7EAF930E0D0CC@CH1PRD0310MB381.namprd03.prod.outlook.com>
References: <1349654347-18337-1-git-send-email-kys@microsoft.com>
 <1349654386-18378-1-git-send-email-kys@microsoft.com>
 <20121008004358.GA12342@kroah.com>
 <426367E2313C2449837CD2DE46E7EAF930A1FB31@SN2PRD0310MB382.namprd03.prod.outlook.com>
 <20121008133539.GA15490@kroah.com>
 <20121009124755.ce1087b4.akpm@linux-foundation.org>
 <426367E2313C2449837CD2DE46E7EAF930DF7FBB@SN2PRD0310MB382.namprd03.prod.outlook.com>
 <20121105134456.f655b85a.akpm@linux-foundation.org>
 <426367E2313C2449837CD2DE46E7EAF930DFA7B8@SN2PRD0310MB382.namprd03.prod.outlook.com>
 <alpine.DEB.2.00.1211051418560.5296@chino.kir.corp.google.com>
In-Reply-To: <alpine.DEB.2.00.1211051418560.5296@chino.kir.corp.google.com>
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> -----Original Message-----
> From: David Rientjes [mailto:rientjes@google.com]
> Sent: Monday, November 05, 2012 5:33 PM
> To: KY Srinivasan
> Cc: Andrew Morton; Greg KH; olaf@aepfle.de; linux-kernel@vger.kernel.org;
> andi@firstfloor.org; apw@canonical.com; devel@linuxdriverproject.org; linux-
> mm@kvack.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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