B.78.3. RHBA-2010:0855 — qemu-kvm bug fix update

Updated qemu-kvm packages that fix various bugs are now available for Red Hat Enterprise Linux 6.
KVM (Kernel-based Virtual Machine) is a full virtualization solution for Linux on AMD64 and Intel 64 systems. qemu-kvm is the user-space component for running virtual machines using KVM.
Bug Fixes
Prior to this update, virtio-net used a packet transmission algorithm that was using a timer to delay a transmission in an attempt to batch multiple packets together. However, this typically resulted in a higher latency. With this update, the default algorithm has been changed to use an asynchronous bottom half transmitter, improving the performance.
Due to error in the committed_memory() function, the ksmtuned service was unable to determine the correct amount of memory used by qemu-kvm processes when no such process existed. This has been fixed, the relevant part of the source code has been corrected to return 0 when no qemu-kvm process is found, and ksmtuned now works as expected.
Previously, attempting to commit a copy-on-write image to a raw backing disk image using the "quemu-img commit" command may have failed with the following error:
qemu-img: Error while committing image
With this update, this error no longer occurs, and such images can now be committed as expected.
All users are advised to upgrade to these updated packages, which fix these bugs.