I understand the idea behind ballooning as " it effectively increases or decreases the amount of physical memory given to the guest, with the help of the guest's native memory management algorithms". The benefit is obvious in cases where the hypervisor does a hard partitioning of the memory between the guests. The guest vm (virtual memory manager) will indirectly say that these are my least used pages, or the safest candidates for eviction.
But in case of kvm, the guest memory is itself allocated and managed by the host linux vm. So, suppose if the guest evicts a lru page (which might even not actually reside in host physical memory at the time) and even the host chooses a lru page for eviction, the host decision is better in a sense that this page is definitely residing in the physical memory. So, are we gaining from using a balloon driver in the guest. The only difference I see is that the balloon driver will always be giving us a page used by the guest. On the other hand, the linux vm will select a page from the entire physical memory, so it might penalise a host application page. But I don't see any benefit because of this. In fact for smaller no. of pages, most likely the guest will choose the pages which have already been swapped out by the host linux vm (the more recently used pages are the one which actually stay in the physical memory). Am I missing something ? I hope I have made the reason for my confusion clear. Also, I have read about some 'balloon userspace component' in kvm, what does it do ? Does it talk to the virtio balloon driver in the linux and keeps giving us some statistics for monitoring purposes ? Is there any other use ? Where can I get the source for this balloon userspace component ? ( I read that Avi is going to merge it, but can I have a look at it now (any patch) ? -- Thanks and Regards, Sukanto Ghosh -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
