On Tue, Apr 5, 2011 at 8:06 AM, Alberto Treviño <[email protected]> wrote:
> On Monday, April 04, 2011 8:37:09 PM Robert LeBlanc wrote: > > Be careful, the host needs to know how the ballooning is working. When > > the guest driver balloons, it tells the host which memory pages are in > > the balloon. The host then trashes those pages and uses them for > > something else. When the guest is pressured for memory and the balloon > > deflates, the host will have to either swap those pages to disk to > > release them as in the case of being used as disk cache. You can't just > > use any balloon technique, KVM needs to understand and coordinate with > > it. Unfortunately I don't know enough about KVM, I only use it for a > > couple of Windows only apps that I tried really hard to get to work > > under WINE and couldn't on my netbook. I can tell you all about VMware's > > memory ballooning, page sharing and compression though. > > I haven't used ballooning in KVM either. I have used in VMware and after a > few months I turned it off. It managed to thrash one of my critical Linux > VMs when, in my opinion, it didn't need to. So now I just plan resources > well, and make sure not to give an VM more than it needs. > I always suggest that in order to prevent too much ballooning, that one sets a reservation for the active memory in a VM. This will prevent the balloon from swapping out too much memory, but you still get the benefit of it. In VMware, I look at the memory for the last month, find the active memory average and give it about 20% more for a reservation and I've over committed memory 3:1 without many problems. Robert
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