Edwards, Nigel \(Nigel Edwards\)
2006-Jan-06 11:18 UTC
[Xen-users] Guidelines for Dom0 memory
Is anybody aware of any work on guidelines for Dom0 memory settings - the dom0_mem parameter for the Dom0 boot? Is there an easy way to determine a minimum value? Does virtual I/O and sharing of memory pages with Dom0 have an effect that needs to be accounted for? There doesn''t seem to be a lot about this in the Xen documentation. I''d really rather not allocate memory to Dom0 that isn''t needed. Cheers, Nigel. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> Is anybody aware of any work on guidelines for Dom0 memory settings - > the dom0_mem parameter for the Dom0 boot? Is there an easy way to > determine a minimum value?I run with 128 MB for dom0. Don''t think it is worth adjusting it more down. I have 5 guest domains that run via LVM and dom0 uses about 60 MB itself. You will need something for the python stuff etc. (using xen 2.0.6).> Does virtual I/O and sharing of memory pages with Dom0 have an effect > that needs to be accounted for?Definitely. If you use loopback devices for hosting guest file systems, dom0 caches all that I/O and that loads dom0 considerably mem-wise. I started using loopback devices and found that whenever I wanted to login to dom0 there would be a noticeable delay (about one second) before getting a login prompt (ssh access). After having switched to LVM I see no more delay and memory load is much less in dom0.> There doesn''t seem to be a lot about this in the Xen > documentation. I''d > really rather not allocate memory to Dom0 that isn''t needed.Me too. Haven''t looked for much more docs since I brought this up on the mailing list some time ago though. Cheers -- Jan Holst Jensen, Novo Nordisk, Denmark _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
My box runs Debian Sarge with xen 2.0.7, LVM and 6 guest domains and seems to be happy with just 64M. Running top reveals that it is using zero swap and still has 30MB of free ram. However, my host domain is purely used for hosting xen and nothing else. I started off with 32MB, but found it started to struggle a little then up''ed it to 64. W ----- Original Message ----- From: "JHJE (Jan Holst Jensen)" <jhje@novonordisk.com> To: "Edwards, Nigel (Nigel Edwards)" <nigel.edwards@hp.com>; <xen-users@lists.xensource.com> Sent: Friday, January 06, 2006 11:47 AM Subject: RE: [Xen-users] Guidelines for Dom0 memory> Is anybody aware of any work on guidelines for Dom0 memory settings - > the dom0_mem parameter for the Dom0 boot? Is there an easy way to > determine a minimum value?I run with 128 MB for dom0. Don''t think it is worth adjusting it more down. I have 5 guest domains that run via LVM and dom0 uses about 60 MB itself. You will need something for the python stuff etc. (using xen 2.0.6).> Does virtual I/O and sharing of memory pages with Dom0 have an effect > that needs to be accounted for?Definitely. If you use loopback devices for hosting guest file systems, dom0 caches all that I/O and that loads dom0 considerably mem-wise. I started using loopback devices and found that whenever I wanted to login to dom0 there would be a noticeable delay (about one second) before getting a login prompt (ssh access). After having switched to LVM I see no more delay and memory load is much less in dom0.> There doesn''t seem to be a lot about this in the Xen > documentation. I''d > really rather not allocate memory to Dom0 that isn''t needed.Me too. Haven''t looked for much more docs since I brought this up on the mailing list some time ago though. Cheers -- Jan Holst Jensen, Novo Nordisk, Denmark _______________________________________________ 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
William Man schrieb:>My box runs Debian Sarge with xen 2.0.7, LVM and 6 guest domains and seems >to be happy with just 64M. Running top reveals that it is using zero swap >and still has 30MB of free ram. >However, my host domain is purely used for hosting xen and nothing else. > >I used to run my dom0s with 128MB (also Debian Sarge and Xen 2.0.7), but I am still using snapshots with LVM and lvm told me that memory is too low until I reserved 256 MB for dom0. Dirk _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Sun, Jan 08, 2006 at 11:51:21AM +0100, Dirk H. Schulz wrote:> William Man schrieb: > > >My box runs Debian Sarge with xen 2.0.7, LVM and 6 guest domains and seems > >to be happy with just 64M. Running top reveals that it is using zero swap > >and still has 30MB of free ram. > >However, my host domain is purely used for hosting xen and nothing else. > > > > > > I used to run my dom0s with 128MB (also Debian Sarge and Xen 2.0.7), but > I am still using snapshots with LVM and lvm told me that memory is too > low until I reserved 256 MB for dom0. >Hmm.. so you have lvm snapshots working OK ? Which kernel? Any additional patches (for lvm) ? Many people have problems (crashes etc) with linux lvm snapshots..> Dirk >-- Pasi Kärkkäinen ^ . . Linux / - \ Choice.of.the .Next.Generation. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users