hello, currently there is one problem with balloon: if we specify too little memory for a domain, that domain might crash with OOM error. even in that case, balloon still happily do what we request. i just accidentally balloon dom0 to 0M, and must reboot the machine ;-) so i guess it is better to enforce a certain limit, so balloon will not bring the amount of memory for a domain to be lower than that level. there are few choices to do this: - each domain has a configurable option for this (for example: balloon-level in domain config file) - xen automatically determine this level for each domain (but how?) any idea? regards, aq _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
It''s probably a job for higher-level management tools. Maybe a safety catch should be placed on ''xm balloon'', but the intra-VM /proc/xen/balloon interface is definitely not intended for the casual user. -- Keir On 18 Jul 2005, at 11:57, aq wrote:> urrently there is one problem with balloon: if we specify too little > memory for a domain, that domain might crash with OOM error. even in > that case, balloon still happily do what we request. i just > accidentally balloon dom0 to 0M, and must reboot the machine ;-) > > so i guess it is better to enforce a certain limit, so balloon will > not bring the amount of memory for a domain to be lower than that > level. > > there are few choices to do this: > - each domain has a configurable option for this (for example: > balloon-level in domain config file)_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On 7/18/05, Keir Fraser <Keir.Fraser@cl.cam.ac.uk> wrote:> It''s probably a job for higher-level management tools. Maybe a safety > catch should be placed on ''xm balloon'', but the intra-VM > /proc/xen/balloon interface is definitely not intended for the casual > user. >fine, but how about the balloon level to set the limit? i prefer to calculate it based on the domain configuration, instead of specifying it in the domain config file. but that is probably a tough job. do you have any idea on how to determine the limit ? regards, aq> -- Keir > > > On 18 Jul 2005, at 11:57, aq wrote: > > > urrently there is one problem with balloon: if we specify too little > > memory for a domain, that domain might crash with OOM error. even in > > that case, balloon still happily do what we request. i just > > accidentally balloon dom0 to 0M, and must reboot the machine ;-) > > > > so i guess it is better to enforce a certain limit, so balloon will > > not bring the amount of memory for a domain to be lower than that > > level. > > > > there are few choices to do this: > > - each domain has a configurable option for this (for example: > > balloon-level in domain config file) > >-- regards, aq _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Mon, 2005-07-18 at 13:38 +0100, Keir Fraser wrote:> It''s probably a job for higher-level management tools. Maybe a safety > catch should be placed on ''xm balloon'', but the intra-VM > /proc/xen/balloon interface is definitely not intended for the casual > user.I still think /proc/xen/balloon makes it far too easy to shoot yourself in the foot, even for the non-casual user. Simply forgetting to leave the units off the end of an echo can bring your domain (even dom0) to a screeching halt. Such as doing: echo 200000 > /proc/xen/balloon instead of: echo 200000K > /proc/xen/balloon. I know that it''s really difficult to determine how low is too low. Could I recommend a small interface change though, that would force the user to always specify units {B,K,M,...}? That might help a little at least. -- Thanks, Paul Larson plars@linuxtestproject.org http://www.linuxtestproject.org _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
> I know that it''s really difficult to determine how low is too low. > Could I recommend a small interface change though, that would force the > user to always specify units {B,K,M,...}? That might help a little at > least.That sounds like it should rule out most accidental errors. Whilst it''s not quite so raw, /proc interfaces tend to be a bit high level anyhow... As an alternative, I guess we could introduce a guest-internal ballooning tool - this could incorporate all the safety checks and user-friendliness (the same or similar checks should be used in the xm tool for the node admin). Cheers, Mark _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On 18 Jul 2005, at 17:12, Mark Williamson wrote:>> I know that it''s really difficult to determine how low is too low. >> Could I recommend a small interface change though, that would force >> the >> user to always specify units {B,K,M,...}? That might help a little at >> least. > > That sounds like it should rule out most accidental errors. Whilst > it''s not > quite so raw, /proc interfaces tend to be a bit high level anyhow... > > As an alternative, I guess we could introduce a guest-internal > ballooning tool > - this could incorporate all the safety checks and user-friendliness > (the > same or similar checks should be used in the xm tool for the node > admin).Really, if you want to safely balloon inside a guest VM, is it so hard to write a tiny script to ensure a ''sane'' value is passed to the /proc interface? The /proc interface is only really text read/write so that accesses are scriptable. If you go straight at it and mess it up, I think that is tough luck. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel