4-11
Safety Information and Technical Specifi cations
Notes on InterruptThrottleRate
Since 7.3.x, the driver has two adaptive modes (setting 1 or 3) in which it dynami-
cally adjusts the InterruptThrottleRate value based on the traffi c that it receives.
After determining the type of incoming traffi c in the last timeframe, it will adjust the
InterruptThrottleRate to an appropriate value for that traffi c.
The algorithm classifi es the incoming traffi c every interval into classes. Once the
class is determined, the InterruptThrottleRate value is adjusted to suit that traffi c
type the best. There are three classes defi ned: “Bulk traffi c”, for large amounts of
packets of normal size; “Low latency”, for small amounts of traffi c and/or a signifi cant
percentage of small packets; and “Lowest latency”, for almost completely small
packets or minimal traffi c.
In dynamic conservative mode, the InterruptThrottleRate value is set to 4000 for
traffi c that falls in class “Bulk traffi c”. If traffi c 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 traffi c in class “Lowest latency”.
Setting InterruptThrottleRate to 0 turns off any interrupt moderation and may im-
prove small packet latency, but is generally not suitable for bulk throughput traffi c
NOTE: InterruptThrottleRate takes precedence over the TxAbsIntDelay and Rx-
AbsIntDelay parameters. In other words, minimizing the receive and/or transmit
absolute delays does not force the controller to generate more interrupts than what
the Interrupt Throttle Rate allows.
CAUTION: If you are using the Intel(R) PRO/1000 CT Network Connection (control-
ler 82547), setting InterruptThrottleRate to a value greater than 75,000, may hang
(stop transmitting) adapters
under certain network conditions. If this occurs a NETDEV WATCHDOG message
is logged in the system event log. In addition, the controller is automatically reset,
