<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">just reading about vmware, it says it need
<p class="line862"> 'needs proprietary kernel modules'</p><br><br>I don't like the sound of that ;-).<br><br>Thing that gets me about virtual machines is memory usage, it all well and good on<br>a single machine (non vm) you can have say 1GB of ram and setup 2GB of swap space,<br>but linux seems rather lazy about claiming and reclaiming memory, if I look at my own<br>machine I have 1GB of ram, and currently using 787MB of swap! This would cause<br>havoc in a virtual environment.... okay I need a memory upgrade.<br><br>Until linux applications constrain their memory use , or they can be given hints on<br>maximum or minimum memory use then using any virtual machine technology that<br>support paging to disk, is a no no.<br><br>paging to disk is not usually a bit problem, as only one machine is effected, and that<br>machine has already exhausted it's memory , so a slow down is expected. Misbehaving<br>VM's that are paging will
effect performance of all vm's on that system.<br><br>Take Apache for example, this always seems to grow in size, it will fork() more depending<br>on it's load, using more memory in the process, I've never seen it release memory ,<br>unless you restart the entire process. :-(. Obviously you can tune it, but be great<br>if this, and other app were aware they we're being virtualised, and tuned their memory<br>allocation accordingly..<br>.<br>So, perhaps applications should become more vm aware? Programmers should stop thinking that memory is infiite resources, and stop assuming that if they allocate more memory than is available then, the kernel/libc will just 'sort it out for them'. Memory leaks on<br>one vm's app's could potential effect others.. <br><br>Linux still suffers from memory leaks , they get fixed, I was told once that the unix<br>mount command leaks lots of memory, sure you only ever run it, it does it job<br>and it quits (linux then
reclaims memory) but that's not excuse for sloppy code.<br><br>Java VM seems a bit more promising, at least you can force garbage collection in<br>low memory situations.<br><br>But what is the solution to this, large disk administrators setup up temp area's, where<br>users can create very large working files but for a limited amount of time? Perhaps<br>this needs to be implemented in memory management too? Okay, mr apache you can<br>double your memory size for but only for x amount of time.<br><br>Openvz seems to stay away from virtual memory, and allows you you to allocate<br>min and max pages, but it's rather a black magic do with your wetting your<br>finger and putting it the air.<br><br>For my installed I've just pack as much ram as possible in , to avoid unnecessary swapping.<br><br>I'd be interested about commercial vm solutions, do they have a magic bullet for<br>memory
management?<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br> <br><br><br><br><br><br><br><br><br>--- On <b>Wed, 1/10/08, gordon dunlop <i><astrozubenel@googlemail.com></i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;">From: gordon dunlop <astrozubenel@googlemail.com><br>Subject: Re: [dundee] VMWare Server 2.0<br>To: toxicnaan@yahoo.co.uk, "Tayside Linux User Group" <dundee@lists.lug.org.uk><br>Date: Wednesday, 1 October, 2008, 8:31 AM<br><br><pre>2008/9/30 Lee Hughes <toxicnaan@yahoo.co.uk>:<br>> well, Gordon, you can't sell me on vmware,<br><br>Lee I am not trying to sell anybody anything, when it comes to which<br>virtualisation technology to use it is horses for courses i.e. user<br>requirements. I am just noticing the rapid improvement in the free<br>offerings that VMWare are giving out
(due to virtualisation<br>competition hotting up). Red Hat have recently bought Qumranet, the<br>company behind KVM which is in the Linux kernel. Whilst Xen is the<br>virtualisation technology of choice for Red Hat, the rationale behind<br>this acquisition is to maintain the open source nature of KVM and to<br>develop it within the Linux kernel. So as KVM development improves its<br>functionality, there will be a time when there is a total Linux kernel<br>virtualisation solution and no-one will really need Virtual Box,<br>VMWare or Xen. A couple of years ago there was talk of having Xen and<br>OpenVZ fully implemented within the Linux kernel, whilst there are<br>large chunks of code from Xen and OpenVZ within the Linux kernel, this<br>has never happened.<br><br>Gordon<br><br><br><br><br><br>> Cheers,<br>> Lee<br>> 'your reality is my virtual
machine'<br>><br>><br>><br>><br><br>_______________________________________________<br>dundee GNU/Linux Users Group mailing list<br>dundee@lists.lug.org.uk http://dundee.lug.org.uk<br>https://mailman.lug.org.uk/mailman/listinfo/dundee<br>Chat on IRC, #tlug on dundee.lug.org.uk<br></pre></blockquote></td></tr></table><br>