Issue 11
© Solarflare Communications 2014
288
Solarflare Server Adapter
User Guide
Other Considerations
PCI Express Lane Configurations
The PCI Express (PCIe) interface used to connect the adapter to the server can function at different
widths. This is independent of the physical slot size used to connect the adapter. The possible widths
are multiples x1, x2, x4, x8 and x16 lanes of (2.5Gbps for PCIe Gen 1, 5.0 Gbps for PCIe Gen 2) in each
direction. Solarflare Adapters are designed for x8 lane operation.
On some server motherboards, choice of PCIe slot is important. This is because some slots (including
ones that are physically x8 or x16 lanes) may only electrically support x4 lanes. In x4 lane slots,
Solarflare PCIe adapters will continue to operate, but not at full speed. The Solarflare driver will warn
you if it detects the adapter is plugged into a PCIe slot which electrically has fewer than x8 lanes.
For SFN5xxxx adapters, which require a PCIe Gen 2 slot for optimal operation, a warning will be given
if they are installed in a PCIe Gen 1 slot.
CPU Power Management
This feature monitors CPU utilization and lowers the CPU frequency when utilization is low. This
reduces the power consumption of the CPU. For latency sensitive applications, where the
application switches between having packets to process and having periods of idle time waiting to
receive a packet, dynamic clock speed control may increase packet latencies. There therefore can be
a benefit to disabling the service.
The service can be disabled temporarily with the configuration in
/etc/power.conf
file and
restarting the service. For example:
cpupm disable
system-threshold always-on
cpu-threshold always-on
cpu_deep_idle disable
The service can be disabled across reboots with:
svcadm disable svc:/system/power:default
See
http://docs.oracle.com/cd/E19253-01/817-0547/gfgmu/index.html
Memory bandwidth
Many chipsets use multiple channels to access main system memory. Maximum memory
performance is only achieved when the chipset can make use of all channels simultaneously. This
should be taken into account when selecting the number of DIMMs to populate in the server.
Consult the motherboard documentation for details.
Server Motherboard, Server BIOS, Chipset Drivers
Tuning or enabling other system capabilities may further enhance adapter performance. Readers
should consult their server user guide. Possible opportunities include tuning PCIe memory controller
(PCIe Latency Timer setting available in some BIOS versions).