On Sat December 12 2009, Avi Kivity wrote: > On 12/11/2009 11:43 PM, rek2 wrote: > > Hi everyone, I'm new to the list and I have a couple questions that we > > are wondering about here at work... > > we have notice that the KVM processes on the host take much more > > memory than the memory we have told the VM to use.. a ruff example.. > > if we tell KVM to use 2 gigs for one VM it will end up showing on the > > host process list for that VM like 3 gigs or more... > > Why do I ask this? well we need to figure out how much memory to add > > to our host server so we can calculate the number of VM's we can run > > there etc etc.. > > Can you give an example? A snapshot from 'top' would do. > I have the opposite happen, when a VM is started, RES is usually lower than -m, which I find slightly odd. But makes sense if qemu/kvm don't actually allocate memory from the host till its requested the first time (if only it would return some of it afterwards, it would be even better). I just fully shut down and restarted on of my vms, which is set to use 128-256 MB ram max. RES is like 72MB on start, and VIRT is 454M. RES generally gets up around 120MB ram when its doing something. One thing I do find a little odd is one of my VMs which is allocated 512MB ram, has a VIRT of 826MB ram. I didn't realize that qemu had so many lib dependencies. Due to kvm not supporting giving memory back, besides by swapping large portions of unused guest ram, my host currently has over 1G used swap. Not particularly happy with that, but it doesn't seem to effect performance too much (except that it generally likes to swap host processes first, guest performance is decent, but host, not so much). -- Thomas Fjellstrom tfjellstrom@xxxxxxx -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
