Hey chaps, having a minor dispute with a friend. According the README in the Xen sources.... " The Xen command line takes a number of optional arguments described in the manual. The most common is ''dom0_mem=xxxM'' which sets the amount of memory to allocate for use by your initial virtual machine (known as domain 0). Note that Xen itself reserves about 32MB memory for internal use, which is not available for allocation to virtual machines. .." I''ve taken this to mean that one allocates say, half of one''s RAM to dom0 with the command `dom0_mem=xxxM`. The domUs will then use up to the other half of the box''s RAM. Is this correct? My buddy says that this is unnecessary as the dom0 only needs 32M of ram. It will give the RAM away to the domU chaps until it has no more RAM to spare. -- John Maclean - 07739 171 531 MSc (DIC) _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> Hey chaps, having a minor dispute with a friend. According the README > in the Xen sources....I''m getting an amusing mental image of people all over the world, in the pub, ignoring the football scores and arguing about Xen with their mates :-)> " > The Xen command line takes a number of optional arguments described > in the manual. The most common is ''dom0_mem=xxxM'' which sets the > amount of memory to allocate for use by your initial virtual > machine (known as domain 0). Note that Xen itself reserves about > 32MB memory for internal use, which is not available for allocation > to virtual machines. > .." > > I''ve taken this to mean that one allocates say, half of one''s RAM to > dom0 with the command `dom0_mem=xxxM`. The domUs will then use up to > the other half of the box''s RAM. Is this correct? > > My buddy says that this is unnecessary as the dom0 only needs 32M of > ram. It will give the RAM away to the domU chaps until it has no more > RAM to spare.Both correct. You can either set the dom0 memory on the commandline leaving the rest available to domUs (this was the standard mode of operation for a long time), or you can have dom0 take all the memory, then balloon itself down to make room for other guests. The auto-ballooning code also allows you to specify a minimum size dom0 will balloon down to (auto-ballooning might be default on now, I think, but you don''t have to use it). HTH, Mark -- Dave: Just a question. What use is a unicyle with no seat? And no pedals! Mark: To answer a question with a question: What use is a skateboard? Dave: Skateboards have wheels. Mark: My wheel has a wheel! _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On 19 Oct 2006 at 22:43, john maclean wrote:> Hey chaps, having a minor dispute with a friend. According the README > in the Xen sources.... > " > The Xen command line takes a number of optional arguments described > in the manual. The most common is ''dom0_mem=xxxM'' which sets the > amount of memory to allocate for use by your initial virtual > machine (known as domain 0). Note that Xen itself reserves about > 32MB memory for internal use, which is not available for allocation > to virtual machines. > .." > > I''ve taken this to mean that one allocates say, half of one''s RAM to > dom0 with the command `dom0_mem=xxxM`. The domUs will then use up to > the other half of the box''s RAM. Is this correct? > > My buddy says that this is unnecessary as the dom0 only needs 32M of > ram. It will give the RAM away to the domU chaps until it has no more > RAM to spare. >Hi, let me add: I got the idea that all DomUs take their RAM from the Dom0 RAM, so if I limit the RAM of Dom0, will I waste RAM? Maybe some documentation about memory management should be added to the user manual... Regards, Ulrich> -- > John Maclean - 07739 171 531 > MSc (DIC) > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Fri, Oct 20, 2006 at 12:37:01AM +0100, Mark Williamson wrote:> > Hey chaps, having a minor dispute with a friend. According the README > > in the Xen sources.... > > I''m getting an amusing mental image of people all over the world, in the pub, > ignoring the football scores and arguing about Xen with their mates :-)I can attest that this has happened more than once ... Steve -- http://www.steve.org.uk/ _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> -----Original Message----- > From: xen-users-bounces@lists.xensource.com > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of > john maclean > Sent: 19 October 2006 22:44 > To: xen-users@lists.xensource.com > Subject: [Xen-users] allocating memory to dom0 > > Hey chaps, having a minor dispute with a friend. According the README > in the Xen sources.... > " > The Xen command line takes a number of optional arguments described > in the manual. The most common is ''dom0_mem=xxxM'' which sets the > amount of memory to allocate for use by your initial virtual > machine (known as domain 0). Note that Xen itself reserves about > 32MB memory for internal use, which is not available for allocation > to virtual machines. > .." > > I''ve taken this to mean that one allocates say, half of one''s RAM to > dom0 with the command `dom0_mem=xxxM`. The domUs will then use up to > the other half of the box''s RAM. Is this correct? > > My buddy says that this is unnecessary as the dom0 only needs 32M of > ram. It will give the RAM away to the domU chaps until it has no more > RAM to spare.Neither of you are directly wrong... You can let Dom0 sacrifice it''s own memory for the DomU - I personally prefer to know where I stand - if I lock Dom0 to (say) 256MB, then I know how much memory is available to DomU''s. You may be able to run a Dom0 on 32MB, but I''d say that you need a bit more than that if you''re using a standard installation, 100MB+ would be more realistic. One reason to use a fixed Dom0 memory amount is that some Kernel allocations are based on percentages of the memory, and once they have been made, the can''t be trivially changed, which means that there may be (say) 5% of the 16GB of RAM used for some buffer-space or such (5% of 16GB is 820 MB). If you set the dom0_mem to 256MB, the kernel will use 5% of 256MB for that buffer, and you''ll have those 800MB available later on. There is a setting in the file /etc/xend-config.sxp that sets how much minimum Dom0 memory is. Not sure what the default is - it can be changed up or down. -- Mats> > -- > John Maclean - 07739 171 531 > MSc (DIC) > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users > > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> > I''m getting an amusing mental image of people all over the world, in the > > pub, ignoring the football scores and arguing about Xen with their mates > > :-) > > I can attest that this has happened more than once ...Actually, I tends to happen when we go down the pub :-) In a parallel dimension, everybody goes to the pub to watch Xen domains boot on a big screen, while a few geeks sit in the corner and talk about ball games :-D Cheers, Mark -- Dave: Just a question. What use is a unicyle with no seat? And no pedals! Mark: To answer a question with a question: What use is a skateboard? Dave: Skateboards have wheels. Mark: My wheel has a wheel! _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
I''m currently living abroad in Manila (Philippines) and Xen is beginning to make its impact in net cafe''s. The advantages are obvious because customers can come back to their ''own'' computer another day. HVM support has also really skyrocketed interest in Xen for that purpose, I get a few calls a week from friends who need help setting it up. Electricity here is rather expensive, but hardware is cheap. One good newer dual core Athalon, a few cheap video cards, a few cheap audio cards and a few cheap usb cards can give you a ''pod'' of 5 or so workstations from a single server. Xen + VLC is also being used quite a bit here in vide-oke joints that offer "private" booths where you can more comfortably make a fool of yourself. Anyway, the alternate dimension is Asia. There''s a "root" cafe where the virtualization geeks hang out complaining about the bastardization of open source and get drunk while the rest watch their dom-u''s boot up (and get drunk) .. Best, -Tim On Sat, 2006-10-21 at 03:41 +0100, Mark Williamson wrote:> > > I''m getting an amusing mental image of people all over the world, in the > > > pub, ignoring the football scores and arguing about Xen with their mates > > > :-) > > > > I can attest that this has happened more than once ... > > Actually, I tends to happen when we go down the pub :-) > > In a parallel dimension, everybody goes to the pub to watch Xen domains boot > on a big screen, while a few geeks sit in the corner and talk about ball > games :-D > > Cheers, > Mark >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> -----Original Message----- > From: xen-users-bounces@lists.xensource.com > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of > Ulrich Windl > Sent: 20 October 2006 07:52 > To: xen-users@lists.xensource.com > Subject: Re: [Xen-users] allocating memory to dom0 > > On 19 Oct 2006 at 22:43, john maclean wrote: > > > Hey chaps, having a minor dispute with a friend. According > the README > > in the Xen sources.... > > " > > The Xen command line takes a number of optional > arguments described > > in the manual. The most common is ''dom0_mem=xxxM'' which sets the > > amount of memory to allocate for use by your initial virtual > > machine (known as domain 0). Note that Xen itself reserves about > > 32MB memory for internal use, which is not available for > allocation > > to virtual machines. > > .." > > > > I''ve taken this to mean that one allocates say, half of one''s RAM to > > dom0 with the command `dom0_mem=xxxM`. The domUs will then use up to > > the other half of the box''s RAM. Is this correct? > > > > My buddy says that this is unnecessary as the dom0 only needs 32M of > > ram. It will give the RAM away to the domU chaps until it > has no more > > RAM to spare. > > > > Hi, > > let me add: I got the idea that all DomUs take their RAM from > the Dom0 RAM, so if > I limit the RAM of Dom0, will I waste RAM? Maybe some > documentation about memory > management should be added to the user manual...Xen keeps track of ALL the memory in the system, and it''s got two different methods of allocating memory: From the "free memory" or "from Dom0". That''s listed in the order of priority, so if there''s "free memory", Xen will use that, and when that''s exhausted, it will attempt to use Dom0 memory until it reaches the minimum size for Dom0 (or something goes wrong and the system crashes). If you know what size your Dom0 will be able to operate under, you should set dom0_mem=<size> in your boot configuration file (grub.conf/menu.lst or whatever it''s called in your system). -- Mats> > Regards, > Ulrich > > > > -- > > John Maclean - 07739 171 531 > > MSc (DIC) > > > > _______________________________________________ > > Xen-users mailing list > > Xen-users@lists.xensource.com > > http://lists.xensource.com/xen-users > > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users > > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users