From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx128.postini.com [74.125.245.128]) by kanga.kvack.org (Postfix) with SMTP id 995FC6B0044 for ; Thu, 8 Nov 2012 08:29:41 -0500 (EST) Received: from mail164-ch1 (localhost [127.0.0.1]) by mail164-ch1-R.bigfish.com (Postfix) with ESMTP id 742B92010C for ; Thu, 8 Nov 2012 13:28:39 +0000 (UTC) From: KY Srinivasan Subject: RE: [PATCH 1/2] mm: Export vm_committed_as Date: Thu, 8 Nov 2012 13:28:32 +0000 Message-ID: <426367E2313C2449837CD2DE46E7EAF930DFC381@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> <426367E2313C2449837CD2DE46E7EAF930DFA7B8@SN2PRD0310MB382.namprd03.prod.outlook.com> <20121106090539.GB21167@dhcp22.suse.cz> 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: Michal Hocko 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 , Johannes Weiner , Ying Han > -----Original Message----- > From: KY Srinivasan > Sent: Tuesday, November 06, 2012 7:53 AM > To: 'Michal Hocko' > Cc: Andrew Morton; Greg KH; olaf@aepfle.de; linux-kernel@vger.kernel.org; > andi@firstfloor.org; apw@canonical.com; devel@linuxdriverproject.org; lin= ux- > mm@kvack.org; Hiroyuki Kamezawa; Johannes Weiner; Ying Han > Subject: RE: [PATCH 1/2] mm: Export vm_committed_as >=20 >=20 >=20 > > -----Original Message----- > > From: Michal Hocko [mailto:mstsxfx@gmail.com] On Behalf Of Michal Hocko > > Sent: Tuesday, November 06, 2012 4:06 AM > > To: KY Srinivasan > > Cc: Andrew Morton; Greg KH; olaf@aepfle.de; linux-kernel@vger.kernel.or= g; > > andi@firstfloor.org; apw@canonical.com; devel@linuxdriverproject.org; l= inux- > > mm@kvack.org; Hiroyuki Kamezawa; Johannes Weiner; Ying Han > > Subject: Re: [PATCH 1/2] mm: Export vm_committed_as > > > > On Mon 05-11-12 22:12:25, KY Srinivasan wrote: > > > > > > > > > > -----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@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 Sat, 3 Nov 2012 14:09:38 +0000 > > > > KY Srinivasan wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > Ok, but you're going to have to get the -mm developers to agr= ee that > > > > > > > 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. > > > > > > > > > > > > > Well, I do have some qualms about exporting vm_committed_as to > modules. > > > > > > > > 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. > > > > > > > > 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. > > > > > > > > > > > > I don't think these qualms are serious enough to stand in the way o= f > > > > this patch, but I'd be interested in hearing the memcg developers' > > > > thoughts on the matter? > > > > > > > > > > > > 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 alternati= ve > > > > 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 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. > > > > So IIUC it will be guest who reports the value and the guest runs in th= e > > ring-0 so it is not in any user process context, right? > > If this is correct then memcg doesn't play any role here. >=20 > Thanks Michal. Yes, the kernel driver reports this metric to the host. > Andrew, let me know how I should proceed here. Ping. Regards, K. Y >=20 > Thanks, >=20 > K. Y -- 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