Re: [libvirt] [RFC] Memory controller exploitation in libvirt

On Tue, Aug 24, 2010 at 11:53:27AM +0530, Nikunj A. Dadhania wrote: > > Subject: [RFC] Memory controller exploitation in libvirt > > Memory CGroup is a kernel feature that can be exploited effectively in the > current libvirt/qemu driver. Here is a shot at that. > > At present, QEmu uses memory ballooning feature, where the memory can be > inflated/deflated as and when needed, co-operatively between the host and > the guest. There should be some mechanism where the host can have more > control over the guests memory usage. Memory CGroup provides features such > as hard-limit and soft-limit for memory, and hard-limit for swap area. Exposing the tunables is nice, but there is another related problem. We don't provide apps enough information to effectively use them. eg, they configure a guest with 500 MB of RAM. How much RAM does QEMU actually use. 500 MB + X MB more. We need to give apps an indication of what the 'X' overhead is. Some of it comes from the video RAM. Some is pure QEMU emulation overhead.

> * Might need to redefine(changing the scope) of existing memory > API. Currently, domainSetMemory is used to set limit_in_bytes in LXC and > memory ballooning in QEmu. While the domainSetMaxMemory is not defined in > QEmu and in case of LXC it is setting the internal object's maxmem > variable. Yep, might need to clarify LXC a little bit.