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Solarflare Server Adapter User Guide
Solarflare Adapters on Windows
Issue 20 © Solarflare Communications 2017 167
Ethernet Frame Length
The maximum Ethernet frame length used by the adapter to transmit data is (or
should be) closely related to the MTU (maximum transmission unit) of your
network. The network MTU determines the maximum frame size that your network
is able to transmit across all devices in the network.
NOTE: For optimum performance set the Ethernet frame length to your network
MTU.
If the network uses Jumbo frames, SAM supports frames up to a maximum of 9216
bytes.
Virtual Machine Queue
Solarflare adapters support VMQ to offload the classification and delivery of
network traffic destined for Hyper ‐ V virtual machines to the network adapter
thereby reducing the CPU load on Hyper ‐ V hosts.
Windows Server 2008 R2 allows the administrator user to statically configure the
number of CPUs available to process interrupts for VMQ. Interrupts are spread
across the specified cores, however the static configuration does not provide best
performance when the network load varies over time.
Dynamic VMQ, supported in Windows Server 2012 and later, will dynamically
distribute received network traffic across available CPUs while adjusting for network
load by, if necessary, bringing in more processors or releasing processors under light
load conditions.
VMQ supports the following features:
• Classification of received network traffic in hardware by using the destination
MAC address (and optionally also the VLAN identifier) to route packets to
different receive queues dedicated to each virtual machine.
• Can use the network adapter to directly transfer received network traffic to a
virtual machine’s shared memory avoiding a potential software ‐ based copy
from the Hyper ‐ V host to the virtual machine.
• Scaling to multiple processors by processing network traffic destined for
different virtual machines on different processors.
Table 38: VMQ Mode Options
Enabled VMQ uses the destination MAC address and
also the VLAN identifier for filtering traffic to
the intended Hyper ‐ V virtual machine.
This is the default.