From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx157.postini.com [74.125.245.157]) by kanga.kvack.org (Postfix) with SMTP id DA0E46B0044 for ; Mon, 5 Nov 2012 17:16:36 -0500 (EST) Received: from mail152-ch1 (localhost [127.0.0.1]) by mail152-ch1-R.bigfish.com (Postfix) with ESMTP id 3FB4F60193 for ; Mon, 5 Nov 2012 22:12:29 +0000 (UTC) From: KY Srinivasan Subject: RE: [PATCH 1/2] mm: Export vm_committed_as Date: Mon, 5 Nov 2012 22:12:25 +0000 Message-ID: <426367E2313C2449837CD2DE46E7EAF930DFA7B8@SN2PRD0310MB382.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> In-Reply-To: <20121105134456.f655b85a.akpm@linux-foundation.org> Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: 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 > -----Original Message----- > From: Andrew Morton [mailto:akpm@linux-foundation.org] > Sent: Monday, November 05, 2012 4:45 PM > To: KY Srinivasan > Cc: Greg KH; olaf@aepfle.de; linux-kernel@vger.kernel.org; andi@firstfloo= r.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 >=20 > On Sat, 3 Nov 2012 14:09:38 +0000 > KY Srinivasan wrote: >=20 > > > > > > > > > > > > Ok, but you're going to have to get the -mm developers to agree tha= t > > > > this is ok before I can accept it. > > > > > > Well I guess it won't kill us. > > > > Andrew, > > > > I presumed this was an Ack from you with regards to exporting the > > symbol. Looks like Greg is waiting to hear from you before he can check > > these patches in. Could you provide an explicit Ack. > > >=20 > Well, I do have some qualms about exporting vm_committed_as to modules. >=20 > vm_committed_as is a global thing and only really makes sense in a > non-containerised system. If the application is running within a > memory cgroup then vm_enough_memory() and the global overcommit policy > are at best irrelevant and misleading. >=20 > If use of vm_committed_as is indeed a bad thing, then exporting it to > modules might increase the amount of badness in the kernel. >=20 >=20 > I don't think these qualms are serious enough to stand in the way of > this patch, but I'd be interested in hearing the memcg developers' > thoughts on the matter? >=20 >=20 > Perhaps you could provide a detailed description of why your module > actually needs this? Precisely what information is it looking for > and why? If we know that then perhaps a more comfortable alternative > can be found. 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 pa= rameters including the memory pressure reported by the guest. Currently, the pressur= e 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 b= y the guest (vm_committed_as) is used as one of the parameters in making the memory bal= ancing decision on the host. This is what Windows guests report to the host. So, I need some m= easure of memory commitments made by the Linux guest. This is the reason I want export vm_co= mmitted_as.=20 Regards, K. Y =20 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org