From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: Re: [PATCH] kvm tools: Add option to specify backing storage for RAM Date: Thu, 21 Apr 2011 16:00:03 +0300 Message-ID: <1303390803.3127.4.camel@stimpy> References: <1303389930-30303-1-git-send-email-levinsasha928@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: mingo@elte.hu, asias.hejun@gmail.com, gorcunov@gmail.com, prasadjoshi124@gmail.com, kvm@vger.kernel.org To: Pekka Enberg Return-path: Received: from mail-ww0-f44.google.com ([74.125.82.44]:50205 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750945Ab1DUNAV (ORCPT ); Thu, 21 Apr 2011 09:00:21 -0400 Received: by wwa36 with SMTP id 36so2066807wwa.1 for ; Thu, 21 Apr 2011 06:00:20 -0700 (PDT) In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Thu, 2011-04-21 at 15:48 +0300, Pekka Enberg wrote: > On Thu, Apr 21, 2011 at 3:45 PM, Sasha Levin wrote: > > Add --use-backing to allow for the usage of a temporary backing file for guest RAM. > > A temporary file is created and aollocated under /tmp and is used to back the RAM memory which is mmaped for the guest. > > There should be enough storage space under /tmp to use this option (at least the size of the guest RAM). > > > > Signed-off-by: Sasha Levin > > OK, but what is this useful for? Why would someone want to do this? It's an alternative to creating more swap. When using large RAM sizes for guests on hosts with limited physical RAM/swap this option gives the user a way to use files instead of swap. This can also be extended to use hugetlbfs. -- Sasha.