From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.12] helo=sc8-sf-mx2.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1Csd5n-0001Ng-B2 for user-mode-linux-devel@lists.sourceforge.net; Sun, 23 Jan 2005 00:27:31 -0800 Received: from fed1rmmtao01.cox.net ([68.230.241.38]) by sc8-sf-mx2.sourceforge.net with esmtp (Exim 4.41) id 1Csd5k-0000GE-VP for user-mode-linux-devel@lists.sourceforge.net; Sun, 23 Jan 2005 00:27:31 -0800 Message-ID: <41F36014.7050905@easyco.com> From: Doug Dumitru MIME-Version: 1.0 Subject: Re: [uml-devel] memory References: <267988DEACEC5A4D86D5FCD780313FBB03B12C4B@exch-03.noida.hcltech.com> In-Reply-To: <267988DEACEC5A4D86D5FCD780313FBB03B12C4B@exch-03.noida.hcltech.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Sun, 23 Jan 2005 00:28:04 -0800 To: "Vaibhav Sharma, Noida" , user-mode-linux-devel@lists.sourceforge.net Vaibhav Sharma, Noida wrote: > Hi, > I have to build a simulator, to check the scalability limits in memory > management of linux. For this, the simulator will provide a large > amount of RAM (in GBs), even if the amout of physical memory is only 512MB. > > Can UML be used for this purpose? I had seen the "mem" option in the > kernel switches option of UML. Can UML simulate such a case? If it does, > how UML handles this? Specifically, can the UML kernel allocate all this > amount of memory (leaving aside the page faults which will be generated > in case of read/write requests to the allocated pages, for it has to use > the actual RAM)? Say, for example if I allocate 4 GB, will the UML > kernel allocate all the amount in the simulated RAM. (maybe it does it > in the some swap, or the /tmp, as the documentation says for the "mem" > usage <_http://user-mode-linux.sourceforge.net/switches.html_> . > > If I have wrong interpretation of the "mem" option in UML, please do > correct me. > > TIA, > Vaibhav Mr. Sharma, What you are trying to do will work, but not for large amounts of memory. UML runs the client using a single user mode memory block as the entire client's core. Thus the clients core size is limited to what a single task can allocate as plain memory. With x86 architechure cpus, this is 2G or 3G depending on how you build a kernel (but usually 2G). There are no paging mechanism here so there is no way to make it "gigabytes" Others can correct me if I have the exact numbers wrong. -- -------------------------------------------------------------------- Doug Dumitru 800-470-2756 (610-237-2000) EasyCo LLC doug@easyco.com http://easyco.com -------------------------------------------------------------------- ------------------------------------------------------- This SF.Net email is sponsored by: IntelliVIEW -- Interactive Reporting Tool for open source databases. Create drag-&-drop reports. Save time by over 75%! Publish reports on the web. Export to DOC, XLS, RTF, etc. Download a FREE copy at http://www.intelliview.com/go/osdn_nl _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel