From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx119.postini.com [74.125.245.119]) by kanga.kvack.org (Postfix) with SMTP id 829D26B0002 for ; Mon, 4 Mar 2013 12:18:06 -0500 (EST) Received: from /spool/local by e33.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 4 Mar 2013 10:18:00 -0700 Received: from d03relay04.boulder.ibm.com (d03relay04.boulder.ibm.com [9.17.195.106]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id 80A7D19D80A8 for ; Mon, 4 Mar 2013 10:06:13 -0700 (MST) Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d03relay04.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r24H697m270360 for ; Mon, 4 Mar 2013 10:06:10 -0700 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r24H68cb013124 for ; Mon, 4 Mar 2013 10:06:08 -0700 Message-ID: <5134D476.3040302@linux.vnet.ibm.com> Date: Mon, 04 Mar 2013 09:05:58 -0800 From: Dave Hansen MIME-Version: 1.0 Subject: Re: [PATCH 1/1] mm: Export split_page(). References: <1362364075-14564-1-git-send-email-kys@microsoft.com> <20130304020747.GA8265@kroah.com> <3a362e994ab64efda79ae3c80342db95@SN2PR03MB061.namprd03.prod.outlook.com> <20130304022508.GA8638@kroah.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: KY Srinivasan Cc: Greg KH , "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" On 03/03/2013 06:36 PM, KY Srinivasan wrote: >> I guess the most obvious question about exporting this symbol is, "Why >> doesn't any of the other hypervisor balloon drivers need this? What is >> so special about hyper-v?" > > The balloon protocol that Hyper-V has specified is designed around the ability to > move 2M pages. While the protocol can handle 4k allocations, it is going to be very chatty > with 4K allocations. What does "very chatty" mean? Do you think that there will be a noticeable performance difference ballooning 2M pages vs 4k? > Furthermore, the Memory Balancer on the host is also designed to work > best with memory moving around in 2M chunks. While I have not seen the code on the Windows > host that does this memory balancing, looking at how Windows guests behave in this environment, > (relative to Linux) I have to assume that the 2M allocations that Windows guests do are a big part of > the difference we see. You've been talking about differences. Could you elaborate on what the differences in behavior are that you are trying to rectify here? >> Or can those other drivers also need/use it as well, and they were just >> too chicken to be asking for the export? :) > > The 2M balloon allocations would make sense if the host is designed accordingly. How does the guest decide which size pages to allocate? It seems like a relatively bad idea to be inflating the balloon with 2M pages from the guest in the case where the guest is under memory pressure _and_ fragmented. -- 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