Dell Intel PRO Family of Adapters - Manual (Page 86)

Parameter
Name Valid Range/Settings Default Description
The algorithm classifies the incoming traffic every inter-
val into classes. Once the class is determined, the Inter-
ruptThrottleRate value is adjusted to suit that traffic type
the best. There are three classes defined: "Bulk traffic",
for large amounts of packets of normal size; "Low
latency", for small amounts of traffic and/or a significant
percentage of small packets; and "Lowest latency", for
almost completely small packets or minimal traffic.
In dynamic conservative mode, the InterruptThrottleRate
value is set to 4000 for traffic that falls in class "Bulk
traffic". If traffic falls in the "Low latency" or "Lowest
latency" class, the InterruptThrottleRate is increased
stepwise to 20000. This default mode is suitable for most
applications.
For situations where low latency is vital such as cluster
or grid computing, the algorithm can reduce latency
even more when InterruptThrottleRate is set to mode 1.
In this mode, which operates the same as mode 3, the
InterruptThrottleRate will be increased stepwise to
70000 for traffic in class "Lowest latency".
Setting InterruptThrottleRate to 0 turns off any interrupt
moderation and may improve small packet latency, but
is generally not suitable for bulk throughput traffic.
NOTES:
l Dynamic interrupt throttling is only applic-
able to adapters operating in MSI or
Legacy interrupt mode, using a single
receive queue.
l When igbvf is loaded with default settings
and multiple adapters are in use sim-
ultaneously, the CPU utilization may
increase non-linearly. In order to limit the
CPU utilization without impacting the over-
all throughput, it is recommended to load
the driver as follows:
modprobe igbvf Inter-
ruptThrottleRate-
e=3000,3000,3000
This sets the InterruptThrottleRate to 3000
interrupts/sec for the first, second, and third
instances of the driver. The range of 2000
to 3000 interrupts per second works on a
majority of systems and is a good starting
point, but the optimal value will be platform-
specific. If CPU utilization is not a concern,
use default driver settings.