24 Sun Dual 10GbE SFP+ PCIe ExpressModule User’s Guide • August 2008
Driver Parameters for Linux Systems
TABLE5-1 lists the tunable ixgbe driver parameters for Linux operating systems and

describes their function.

TABLE5-1 Tunableixgbe Driver Parameters for Linux Operating Systems
Keyword ValidRange DefaultValue Description
FlowControl 0to3
(0=none, 1=Rx
only,2=Tx only,
3=Rx and Tx)
Read fromthe
EEPROM.
If EEPROM is not
detected, default
is 3.
This parameter controlsthe automatic
generation (Tx) and response(Rx) to Ethernet
PAUSEframes.
RxDescriptiors 64 to 512 512 This value is the number of receive descriptors
allocated by the driver.Increasing this value
allows the driver to buffer moreincoming
packets. Each descriptor is 16 bytes. A receive
bufferis also allocated for each descriptor and
can be either 2048, 4056, 8192, or 16384 bytes,
dependingon the MTU setting. When the MTU
size is 1500 or less, the receivebuffer size is
2048bytes. When the MTU is greater than 1500,
the receivebuffer size will be either 4056, 8192,
or 16384 bytes. The maximum MTU size is
16114.
RxIntDelay 0 to 65535
(0=off)
72 This value delays the generation of receive
interrupts in units of 0.8192 microseconds.
Receive interrupt reductioncan improve CPU
efficiencyif properly tuned for specific network
traffic.Increasing this value adds extra latency
to frame receptionand canend up decreasing
the throughputof TCP traffic.If the system is
reportingdropped receives, this value might be
set too high, causing the driver to run out of
available receivedescriptors.
TxDescriptors 80 to 4096 256 Thisvalue is the number of transmit descriptors
allocated by the driver.Increasing this value
allowsthe driver to queue more transmits. Each
descriptor is 16 bytes.
XsumRX 0 to 1 1 A value of 1 indicates that the driver should
enableIP checksum offload for received packets
(both UDP and TCP) to the Ethernet adapter
hardware.