Kvm Networking Performance - Red Hat ENTERPRISE LINUX 5 - VIRTUALIZATION GUIDE Manual

The virtualization extensions are sometimes disabled in BIOS, usually by laptop manufacturers.
Section 34.12, "Enabling Intel VT and AMD-V virtualization hardware extensions in BIOS"
Refer to
instructions on enabling disabled virtualization extensions.
Verify the virtualization extensions are enabled in BIOS. The BIOS settings for Intel® VT or AMD-
V are usually in the Chipset or Processor menus. The menu names may vary from this guide, the
virtualization extension settings may be found in Security Settings or other non standard menu
names.
Procedure 34.1. Enabling virtualization extensions in BIOS
1. Reboot the computer and open the system's BIOS menu. This can usually be done by pressing
the delete key, the F1 key or Alt and F4 keys depending on the system.
Select Restore Defaults or Restore Optimized Defaults, and then select Save & Exit.
2.
3. Power off the machine and disconnect the power supply.
Enabling the virtualization extensions in BIOS
4.
Note: BIOS steps
Many of the steps below may vary depending on your motherboard, processor type,
chipset and OEM. Refer to your system's accompanying documentation for the
correct information on configuring your system.
a. Power on the machine and open the BIOS (as per Step 1).
Open the Processor submenu The processor settings menu may be hidden in the Chipset,
b.
Advanced CPU Configuration or Northbridge.
Enable Intel Virtualization Technology (also known as Intel VT) or AMD-V depending
c.
on the brand of the processor. The virtualization extensions may be labeled Virtualization
Extensions, Vanderpool or various other names depending on the OEM and system BIOS.
d. Enable Intel VTd or AMD IOMMU, if the options are available. Intel VTd and AMD IOMMU
PCI
are used for
Select Save & Exit.
e.
5. Power off the machine and disconnect the power supply.
6. Run cat /proc/cpuinfo | grep vmx svm. If the command outputs, the virtualization
extensions are now enabled. If there is no output your system may not have the virtualization
extensions or the correct BIOS setting enabled.

34.13. KVM networking performance

By default, KVM virtual machines are assigned a virtual Realtek 8139 (rtl8139) NIC (network interface
controller).
The rtl8139 virtualized NIC works fine in most environments. However, this device can suffer from
performance degradation problems on some networks, for example, a 10 Gigabit Ethernet network.
passthrough.
KVM networking performance
for
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