From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751710AbaCFG0m (ORCPT ); Thu, 6 Mar 2014 01:26:42 -0500 Received: from nm6.bullet.mail.bf1.yahoo.com ([98.139.212.165]:42303 "EHLO nm6.bullet.mail.bf1.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751639AbaCFG0k (ORCPT ); Thu, 6 Mar 2014 01:26:40 -0500 X-Yahoo-Newman-Id: 778857.40576.bm@smtp215.mail.bf1.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: jdW2N.QVM1nX9i8YV2xngY4IgeVSfJrejcasDBYbk6ao5iv TvOphYELAR.Ln8FFm1BKj17._YKYJoxSIFDL0jfmnPj6r6dPQd2nRE0S6mUZ vhlFVBnh6Mev79EME8DqAQr7fhpCLe1bSjroYJv0qt.ufxBliZqeB5rfuJfs 6No9FbI49fDTR6bmcOPqiL7RFAPCgBdkzeTAxQDaLSabu3IIDhpEEtwViTWm ipEyCpWGZeqL2X3ytxu05YCcIy933YhlYPDy3shx3zghDQkYIvs6Pfat56yL Th5SMGkWtgAhHMbBw7YbcoLWh4mojDAgXmoa4NIy9RofIQN8NNQzYEVcZwVM zC4okL1G7VnNL9Mq.RWzdZpXGOKvqQq6vnkywMeeBpI41RxCxSR3mqzokpVd syRVi2rpBUvsr2TVULVf.hQdAytB.LeyaunzM.8sQGjo5tMqgPoySHjFZ24H EARsp6gEdjXwqdNaU6.CnO7FaL6vVvkesS7BJD8D4W1xUTWf7uXjK8hjD_tI W7.xA5Z6sGe9TGNyUJQu_Bt7rf6ikF2iGCL3A5ussBH0Ed_QW4D0_WCPskPQ thSZFhKVsISFQlhhV2h6DH17Nm0XAMVZ.9OqdKtmjo3tLVj7bfJZNIHDcLYO YfzsQpQ-- X-Yahoo-SMTP: u9r3j8eswBBsV5z1r5v0bR9cjPS77vatbJK.6sw- X-Rocket-Received: from [192.168.1.24] (draconicpenguin1@173.68.253.136 with plain [98.139.211.125]) by smtp215.mail.bf1.yahoo.com with SMTP; 05 Mar 2014 22:20:45 -0800 PST Message-ID: <531813B4.7060205@yahoo.com> Date: Thu, 06 Mar 2014 01:20:36 -0500 From: Brian Wong User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: linux-kernel@vger.kernel.org Subject: Linux does not use more than the startup RAM under Hyper-V with dynamic memory enabled Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I'm new to LKML, so please don't be too hard on me :) I'm running Gentoo Linux under Microsoft Client Hyper-V on Windows 8.1 Pro, and I've noticed some odd behavior with respect to dynamic memory (aka memory ballooning). The system will never use more than the startup memory defined in the vitual machine's settings. For example, if I set the startup memory to 512 MB, and enable dynamic memory with a minimum of 512 MB and a maximum of 8192 MB, the system will never allocate than 512 MB of physical memory, despite Hyper-V assigning more memory to the VM and the added memory being visible in the output of "free" and "htop". Attempting to use more memory causes the system to start paging to swap, rather than actually allocating the memory above the startup memory assigned to the VM. The kernel is built with the full set of Hyper-V drivers, including the key "Microsoft Hyper-V Balloon Driver" as well as memory hot-add and hot-remove functionality. This is happening with both the Gentoo-patched 3.10.32 kernel and the vanilla 3.12.5 kernel. The host machine has a total of 24 GB of memory. For now, I am working around the issue by starting the VM with the startup memory set to the maximum and letting Hyper-V take the usused memory back when it is not in use. The VM will then get the extra memory when it needs it. Have I encountered a bug in the Hyper-V balloon driver? -- Brian Wong http://www.fierydragonlord.com