[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] [PATCH] PoD: Handle operations properly when domain is dying
Hi George -- A possibly related issue came up in a team discussion yesterday. It is not uncommon for management tools to check available memory to decide if there is sufficient space to provision a new domain, for example when choosing a machine on which to start a new domain. But there is no "lock" so if the answer is yes and the machine is chosen, but moments later some memory becomes used (by PoD or ballooning or ???), domain creation might fail due to insufficient memory. Tmem has a "freeze" feature to avoid this problem, but tmem has the advantage that all domains will continue to function even if tmem is frozen... I'm not sure that's true for PoD. Clearly management tools can be very conservative and assume every domain on a machine is using its maxmem, but that defeats the purpose of much of the overcommitment work we are doing. I know Citrix is working on hypervisor swap, but that has a pretty horrible performance penalty, as well as some interesting functionality limitations/challenges. Any clever ideas on how to deal with this problem in the future? For example, assume someone wants to launch a sequence of PoD domains that will be idle when launched but eventually will utilize all (or even most) of maxmem. Thanks, Dan > -----Original Message----- > From: George Dunlap [mailto:George.Dunlap@xxxxxxxxxxxxx] > Sent: Wednesday, November 11, 2009 8:08 AM > To: xen-devel@xxxxxxxxxxxxxxxxxxx > Subject: [Xen-devel] [PATCH] PoD: Handle operations properly > when domain > is dying > > > Handle PoD operations properly when a domain is dying. > > No populate-on-demand activities should happen when a domain is dying. > Especially, it is a bug for memory to be added to the PoD cache when > d->is_dying is non-zero, since if this happens after the cache has > been emptied, these pages will never be freed. This may cause "zombie > domains" to linger. > > Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx> > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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