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Solarflare Server Adapter User Guide
Solarflare Adapters on Linux
Issue 20 © Solarflare Communications 2017 116
Warning messages can be viewed in
dmesg
from
/var/log/messages
.
The
lspci
command can be used to discover the currently negotiated PCIe lane
width and speed:
lspci ‐ d 1924: ‐ vv

02:00.1 Class 0200: Unknown device 1924:0710 (rev 01)

...

Link: Supported Speed 2.5Gb/s, Width x8, ASPM L0s, Port 1

Link: Speed 2.5Gb/s, Width x8
NOTE: The Supported speed may be returned as 'unknown', due to older
lspci
utilities not knowing how to determine that a slot supports PCIe Gen. 2.0/5.0 Gb/s
or PCIe Gen 3.0/8,0 Gb/s.
In addition, the latency of communications between the host CPUs, system memory
and the Solarflare PCIe adapter may be PCIe slot dependent. Some slots may be
“closer” to the CPU, and therefore have lower latency and higher throughput. If
possible, install the adapter in a slot which is local to the desired NUMA node
Please consult your server user guide for more information.
CPU Speed Service
Most Linux distributions will have the
cpuspeed
service running by default. This
service controls the CPU clock speed dynamically according to current processing
demand. 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 latency. Solarflare
recommend disabling the cpuspeed service if minimum latency is the main
consideration.
The service can be disabled temporarily:
/sbin/service cpuspeed stop
The service can be disabled across reboots:
/sbin/chkconfig –level 12345 cpuspeed off
CPU Power Service
On RHEL7 systems,
cpuspeed
is replaced with
cpupower
. Solarflare recommend
disabling the
cpupower
service if minimum latency is the main consideration. The
service is controlled via
systemctl
:
systemctl stop cpupower

systemctl disable cpupower
Tuned Service
On RHEL7 systems, it may be beneficial to disable the
tuned
service if minimum
latency is the main consideration. Users are advised to experiment. The service is
controlled via
systemctl
:
systemctl stop tuned

systemctl disable tuned