From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx118.postini.com [74.125.245.118]) by kanga.kvack.org (Postfix) with SMTP id D73E56B0005 for ; Mon, 18 Mar 2013 09:45:08 -0400 (EDT) Received: from mail115-co9 (localhost [127.0.0.1]) by mail115-co9-R.bigfish.com (Postfix) with ESMTP id E46AD14015C for ; Mon, 18 Mar 2013 13:44:12 +0000 (UTC) From: KY Srinivasan Subject: RE: [PATCH 2/2] Drivers: hv: balloon: Support 2M page allocations for ballooning Date: Mon, 18 Mar 2013 13:44:05 +0000 Message-ID: <1701384b10204014b53acecb006521b0@SN2PR03MB061.namprd03.prod.outlook.com> References: <1363470088-24565-1-git-send-email-kys@microsoft.com> <1363470125-24606-1-git-send-email-kys@microsoft.com> <1363470125-24606-2-git-send-email-kys@microsoft.com> <20130318105257.GG10192@dhcp22.suse.cz> In-Reply-To: <20130318105257.GG10192@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: "gregkh@linuxfoundation.org" , "linux-kernel@vger.kernel.org" , "devel@linuxdriverproject.org" , "olaf@aepfle.de" , "apw@canonical.com" , "andi@firstfloor.org" , "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "kamezawa.hiroyuki@gmail.com" , "hannes@cmpxchg.org" , "yinghan@google.com" > -----Original Message----- > From: Michal Hocko [mailto:mhocko@suse.cz] > Sent: Monday, March 18, 2013 6:53 AM > To: KY Srinivasan > Cc: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org; > devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com; > andi@firstfloor.org; akpm@linux-foundation.org; linux-mm@kvack.org; > kamezawa.hiroyuki@gmail.com; hannes@cmpxchg.org; yinghan@google.com > Subject: Re: [PATCH 2/2] Drivers: hv: balloon: Support 2M page allocation= s for > ballooning >=20 > On Sat 16-03-13 14:42:05, K. Y. Srinivasan wrote: > > While ballooning memory out of the guest, attempt 2M allocations first. > > If 2M allocations fail, then go for 4K allocations. In cases where we > > have performed 2M allocations, split this 2M page so that we can free t= his > > page at 4K granularity (when the host returns the memory). >=20 > Maybe I am missing something but what is the advantage of 2M allocation > when you split it up immediately so you are not using it as a huge page? The Hyper-V ballooning protocol specifies the pages being ballooned as page= ranges - start_pfn: number_of_pfns. So, when the guest balloon is inflating and I am= able to allocate 2M pages, I will be able to represent 512 contiguous pages in one = 64 bit entry and this makes the ballooning operation that much more efficient. The reason I split the p= age is that the host does not guarantee that when it returns the memory to the guest, it will return in a= ny particular granularity and so I have to be able to free this memory in 4K granularity. This is the corner= case that I will have to handle. Regards, K. Y >=20 > [...] > -- > Michal Hocko > SUSE Labs >=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