Is there any reason why I would not want to set dom0-min-mem to 0 or to what I set dom0_mem on my kernel line? Setting to 0 or setting to the same value as dom0_mem disables memory balloon correct? I cant seem to think of a reason why I would want memory ballooning. Also setting dom0-min-mem should that be done in xend-config.sxp or on the kernel command line? -- Nick Anderson <nick@anders0n.net> http://www.cmdln.org http://www.anders0n.net _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Tue, May 6, 2008 at 5:05 PM, Nick Anderson <nick@anders0n.net> wrote:> Is there any reason why I would not want to set dom0-min-mem to 0 or to what > I set dom0_mem on my kernel line? Setting to 0 or setting to the same value > as dom0_mem disables memory balloon correct? I cant seem to think of a > reason why I would want memory ballooning.As an alternate, just pass dom0_mem=<some number> to the hypervisor via grub. That''s what I always do. No ballooning issues and I can make sure domain 0 is as big or as small as I need it to be (though I never set it below 512M and usually its set to somewhere between 1GB and 4GB depending on the amount of RAM the system has).> Also setting dom0-min-mem should that be done in xend-config.sxp or on the > kernel command line?I''m not positive on this, but I''d say xend-config.sxp. -- ------------------> Jeffrey Lane - W4KDH <------------------- www.jefflane.org Another cog in the great Corporate Wheel The internet has no government, no constitution, no laws, no rights, no police, no courts. Don''t talk about fairness or innocence, and don''t talk about what should be done. Instead, talk about what is being done and what will be done by the amorphous unreachable undefinable blob called "the internet user base." -Paul Vixie _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> Is there any reason why I would not want to set dom0-min-mem to 0You definitely do not want to set it to 0. If you create a new domU you might run out of memory on dom0 and bad things will happen. Setting dom0-min-mem to about 128M (depends how much things you run on dom0) is good safety net.> Also setting dom0-min-mem should that be done in xend-config.sxp or on > the kernel command line?Using xend-config.sxp is enough. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Siim Vahtre wrote:> You definitely do not want to set it to 0. If you create a new domU you > might run out of memory on dom0 and bad things will happen. Setting > dom0-min-mem to about 128M (depends how much things you run on dom0) is > good safety net.# Dom0 will balloon out when needed to free memory for domU. # dom0-min-mem is the lowest memory level (in MB) dom0 will get down to. # If dom0-min-mem=0, dom0 will never balloon out. (dom0-min-mem 196) Perhaps I am just mis-understanding. I take this to mean that domU can steal memory from dom0 up until dom0 gets to the min-mem threshold. And according to the config comments setting to 0 makes dom0 not balloon. So I read that as domU can not ever steal memory from dom0. -- Nick Anderson <nick@anders0n.net> http://www.cmdln.org http://www.anders0n.net _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Nick Anderson wrote on Tue, 06 May 2008 16:21:41 -0500:> I take this to mean that domU can > steal memory from dom0 up until dom0 gets to the min-mem threshold.But if you set it to 0 what *is* the threshold? 0? Kai -- Kai Schätzl, Berlin, Germany Get your web at Conactive Internet Services: http://www.conactive.com _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Kai Schaetzl wrote:> But if you set it to 0 what *is* the threshold? 0?According to the comments in the config # Dom0 will balloon out when needed to free memory for domU. # dom0-min-mem is the lowest memory level (in MB) dom0 will get down to. # If dom0-min-mem=0, dom0 will never balloon out. So I take that to mean setting dom0-min-mem to 0 disables memory ballooning(for dom0). I just want to clarify if that is the way to disable memory ballooning from dom0. I had been told in ##xen that booting with dom0_mem=X effectively disables ballooning. Or is all of this mute if I never allocate more memory that what I have in the physical machine total? -- Nick Anderson <nick@anders0n.net> http://www.cmdln.org http://www.anders0n.net _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Tue, 2008-05-06 at 17:09 -0400, Jeff Lane wrote:> On Tue, May 6, 2008 at 5:05 PM, Nick Anderson <nick@anders0n.net> wrote: > > Is there any reason why I would not want to set dom0-min-mem to 0 or to what > > I set dom0_mem on my kernel line? Setting to 0 or setting to the same value > > as dom0_mem disables memory balloon correct? I cant seem to think of a > > reason why I would want memory ballooning. > > As an alternate, just pass dom0_mem=<some number> to the hypervisor > via grub. That''s what I always do. No ballooning issues and I can > make sure domain 0 is as big or as small as I need it to be (though I > never set it below 512M and usually its set to somewhere between 1GB > and 4GB depending on the amount of RAM the system has).This only sets the initial dom0 memory usage - it does not prevent ballooning. We''ve had problems with ballooning causing networking to stop, so we''ve disabled it, though we did this by setting dom0_mem on boot and dom0-min-mem to the same value in xend-config.sxp John. -- http://www.brightbox.co.uk - UK Ruby on Rails hosting _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> So I take that to mean setting dom0-min-mem to 0 disables memory > ballooning(for dom0). I just want to clarify if that is the way to > disable memory ballooning from dom0. I had been told in ##xen that > booting with dom0_mem=X effectively disables ballooning.I''m not sure that dom0_mem=X will disable ballooning completely on it''s own; I''d expect that Xend will still autoballoon dom0 in order to make space for new domUs, if the dom0-min-mem setting allows it to. So you should disable autoballooning even when using dom0_mem=X if you want it not to happen.> Or is all of this mute if I never allocate more memory that what I have > in the physical machine total?If your domU''s memory allocations can be satisfied without ballooning dom0 then I believe it won''t get ballooned. I''d still advise explicitly disabling it if you really want it not to happen (and I''ve been in the habit of recommending this as a good practice for a server, since you don''t need autoballooning there, typically). This ensures a "safety catch" that prevents dom0 accidentally getting shrunk if you start more domUs than expected without thinking about the available memory. Cheers, Mark _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users