Solarflare Solarflare XtremeScale series, User Manual, Page: 172 / 400

Solarflare Server Adapter User Guide
Solarflare Adapters on Windows
Issue 20 © Solarflare Communications 2017 165
Further Reading
For more information on Windows RSS profiles and options refer to http://
msdn.microsoft.com/en ‐ us/library/windows/hardware/
ff570864%28v=vs.85%29.aspx
4.12 Segmentation Offload
Solarflare adapters offload the tasks of packet segmentation and reassembly to the
adapter hardware, reducing the CPU processing burden and improving
performance.
• Large Send Offload (LSO), when enabled, offloads to the adapter the splitting
of outgoing TCP data into packets. This reduces CPU use and improves peak
throughput. Since LSO has no effect on latency, it can be enabled at all times.
The driver has LSO enabled by default.
• Receive Segment Coalescing (RSC) is a Microsoft feature introduced in
Windows Server 2012. When enabled the adapter will coalesce multiple
received TCP packets on a TCP connection into a single call to the TCP/IP stack.
This reduces CPU use and improves peak performance. RSC has a low impact on
latency. If a host is forwarding received packets from one interface to another
then Windows will automatically disable RSC. RSC is enabled by default.
• Large Receive Offload (LRO) is a Solarflare proprietary mechanism similar to
RSC. It is used when RSC is unavailable (i.e. on Windows Server 2008 R2). When
enabled the adapter will coalesce multiple received TCP packets on a TCP
connection into a single call to the TCP/IP stack. This reduces CPU use and
Max. RSS processor The maximum processor available to RSS. The value is
specified as a group (range 0 ‐ 9) and CPU number (range
0 ‐ 63).
Max. RSS processors The maximum number of processors to be used by RSS.
The value is in the range 0 ‐ 256.
Max. RSS queues The maximum number of receive queues created per
interface. The value is in the range 0 ‐ 64.
NUMA node id The NUMA node id drop down list box is displayed on
Windows platforms that support NUMA architectures.
This constrains the set of CPU cores used for RSS to the
specified NUMA node. Solarflare recommend you leave
this at the default setting of All. The adapter will
attempt to use only processors from the specified
NUMA node for RSS. If this is set to ALL or it is greater
than or equal to the number of NUMA nodes in the
system, all NUMA nodes are used.
Table 36: RSS and Interrupts Options