[libvirt] Virtio Balloon Dynamic behaviour ??

Hi all, I want to be clear in details regarding Virtio balloon Driver in RHEL 6.1 KVM hypervisor In documentations it is written that Virtio balloon driver allow the guest to expand its memory dynamically . Now I want to know the meaning of dynamically ... Whether it means 1) We can change the memory of guest using libvirt API only i.e by using virsh setmem command at runtime (VERIFIED) 2) Or the guest itself can check that it is running out of memory so it request host for some memory and when the host respond by giving back memory it expands its memory size. Which is automation The 1st option is working fine Now can anyone tell me that memory expantion can be done dynamically(point 2) also DISCLAIMER: ----------------------------------------------------------------------------------------------------------------------- The contents of this e-mail and any attachment(s) are confidential and intended for the named recipient(s) only. It shall not attach any liability on the originator or NECHCL or its affiliates. Any views or opinions presented in this email are solely those of the author and may not necessarily reflect the opinions of NECHCL or its affiliates. Any form of reproduction, dissemination, copying, disclosure, modification, distribution and / or publication of this message without the prior written consent of the author of this e-mail is strictly prohibited. If you have received this email in error please delete it and notify the sender immediately. . -----------------------------------------------------------------------------------------------------------------------