Hello, Our router simulation project is moving forward. Right now I''m thinking about how to get the smallest possible kernel for domU. I really need it to consume almost no memory at all... The only thing that will be used inside domU is quagga/zebra routing daemon and sometimes dhttp. Maybe I should go for a 2.4 kernel? Would it be possible to run a 2.4 kernel inside domU? I suppose a 2.6 won''t at least use _less_ memory than a 2.4? Best regards Rickard Borgmäster _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Yes, you can run a 2.4 kernel inside a domU and play with the kernel options to have the minimal configuration to save memory. On Fri, 27 Jan 2006 15:30:06 +0100 Rickard Borgmäster <doktorn@sub.nu> wrote:> Hello, > > Our router simulation project is moving forward. Right now I''m >thinking about how to get the smallest possible kernel for domU. I >really need it to consume almost no memory at all... > > The only thing that will be used inside domU is quagga/zebra routing >daemon and sometimes dhttp. > > Maybe I should go for a 2.4 kernel? Would it be possible to run a >2.4 kernel inside domU? I suppose a 2.6 won''t at least use _less_ >memory than a 2.4? > > Best regards > Rickard Borgmäster > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users----------------------------------------------------------------- Jorge Isaac Davila Lopez - sitio web: http://www.nicaraguaopensource.com/ correo-e: davila@nicaraguaopensource.com - clave pgp: http://www.nicaraguaopensource.com/claves/nos.asc huella digital: F8F4 8563 28D2 29E1 E2EA 9EAB CA0F A96F A3EE 6F56 ----------------------------------------------------------------- _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Jorge Davila wrote:> Yes, you can run a 2.4 kernel inside a domU and play with the kernel > options to have the minimal configuration to save memory.Are kernels compatible between different xen versions? I copied debian 2.4 kernel from xen-2.0 democd and tried to boot is. But I just get Error creating domain: (0, Error) Are there any specific intructions for compiling a xen-compatible 2.4 kernel? Best regards, Rickard _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Rickard Borgmäster wrote:> Are kernels compatible between different xen versions? I copied debian > 2.4 kernel from xen-2.0 democd and tried to boot is. But I just get > Error creating domain: (0, Error) > > Are there any specific intructions for compiling a xen-compatible 2.4 > kernel?Probably should have mentioned that I''m interested in running a 2.4 domU kernel with Xen 3.0. Maybe this isn''t possible? Best regards Rickard _______________________________________________ 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 > Rickard Borgmäster > Sent: 27 January 2006 15:01 > To: xen-users@lists.xensource.com > Subject: [Xen-users] Re: Minimal kernel for domU > > Jorge Davila wrote: > > Yes, you can run a 2.4 kernel inside a domU and play with > the kernel > > options to have the minimal configuration to save memory. > > Are kernels compatible between different xen versions? I copied debian > 2.4 kernel from xen-2.0 democd and tried to boot is. But I > just get Error creating domain: (0, Error) > > Are there any specific intructions for compiling a > xen-compatible 2.4 kernel?I believe that current Xen (3.0, testing, unstable, etc) do not support Kernel 2.4. It''s probably not A LOT of work to make it work, but it''s still some work. However, I have a feeling that the difference in Kernel size wouldn''t be THAT great - if you minimize the 2.6 kernel, how much bigger is it compared to a 2.4 kernel? I don''t know the answer, but I would think that the KERNEL itself isn''t that much difference - 2.6 has MORE FEATURES that you can turn on (or off), but once you''ve got the same feature-set, I would think [I''m guessing!] that the size difference isn''t very much. Are you planning on running VERY many domains with small memory footprint? Consider that the page-tables for just mapping the memory once in a 1GB system takes up one megabyte [or two megabytes if you use PAE]. Obviously, if you''re running multiple tasks, each task would have some amount of page-table entries, possibly including duplicate ones for user-mode mappings of shared memory regions and in some cases also duplicates for the kernel space memory. -- Mats> > Best regards, > Rickard > > > _______________________________________________ > 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
Petersson, Mats wrote:> I believe that current Xen (3.0, testing, unstable, etc) do not > support Kernel 2.4. It''s probably not A LOT of work to make it work,> but it''s still some work. The Xen 3 documentation doesn''t mention 2.4 kernels either, so maybe you''re right.> However, I have a feeling that the difference in Kernel size wouldn''t > be THAT great - if you minimize the 2.6 kernel, how much bigger is it > compared to a 2.4 kernel? I don''t know the answer, but I would think > that the KERNEL itself isn''t that much difference - 2.6 has MORE > FEATURES that you can turn on (or off), but once you''ve got the same > feature-set, I would think [I''m guessing!] that the size difference > isn''t very much.That''s why I''m asking :-) The reason for me coming up with the idea is that the kernel vmlinuz-2.6.12.6-xenU is about 1,1MB while the vmlinuz-2.4.29-xenU (from demoCD) is just 816KB. So I thought it would be worth asking about.> Are you planning on running VERY many domains with small memory> footprint? I don''t know what VERY many domains means to you, but yes, sort of, since everything is relative. What we are trying to accomplish is to build a bootable LiveCD with Xen (this is sort of done already). In the booted knoppix environment, a number of virtual machines should be started up, to run nothing but a routing daemon (quagga / zebra). The goal is to have a Cisco router simulator on a bootable CD-Rom, for students to practice routing scenarions without any physical Cisco routers. Furthermore, the goal is to run 10 virtual routers on a computer with only 256MB ram. This could be done. I know that. Tests with Xen 2.0.7 before Christmas showed that domU''s could boot with only 12MB Ram. Now we''re going for Xen 3, and today the minimum domU memory that will still boot domU, is 17MB. But that is too big. The host can only run 8 domU''s before crashing.> Consider that the page-tables for just mapping the memory once in a > 1GB system takes up one megabyte [or two megabytes if you use PAE]. > Obviously, if you''re running multiple tasks, each task would have some > amount of page-table entries, possibly including duplicate ones for > user-mode mappings of shared memory regions and in some cases also > duplicates for the kernel space memory.I do know some about computers, but the above was a bit too complicated for me I think... Maybe you can translate it to more understandable text now that you know the background. I suspect it might be useful information... Best regards Rickard Borgmäster _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users