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sys_attrs_alt(5)
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sys_attrs_alt - alt subsystem attributes
This reference page lists and describes attributes for the
alt (alt) kernel subsystem. This subsystem is used by the
DEGPA Gigabit Ethernet network interface cards (NICs). The
hardware and firmware for these cards support coalescing,
a threshold that causes the driver to send an interrupt to
the kernel. This threshold can be defined in terms of a
timer or the number of packets sent or received. The
*_coal and *_ticks attributes in the following list support
performance tuning related to coalescing.
Refer to sys_attrs(5) for an introduction to the topic of
kernel subsystem attributes.
The version number of the alt driver. This is a
read-only attribute, and cannot be changed.
The version number of the firmware that is downloaded
to the DEGPA Gigabit Ethernet card. This is
a read-only attribute and cannot be changed.
A value that enables (1) or disables (0) the awakening
of separate threads by the driver's interrupt
service routine to handle completion of transmit
and receive operations. When separate worker
threads are enabled, the system load of the Gigabit
Ethernet driver can be spread over multiple CPUs.
When separate worker threads are disabled, the master
system CPU (or the master CPU in each RAD of a
NUMA system) services all the transmit and receive
operations for the system's DEGPA Gigabit Ethernet
adapters.
Default: 1 (multiple threads enabled)
A 0 setting improves the performance of the driver
software itself. However, overall system performance
is likely to suffer during times of high network
load because kernel applications other than
the driver can have difficulty accessing the master
CPU. Furthermore, the likelihood of overall system
performance degradation goes up with each additional
DEGPA Gigabit Ethernet card supported by the
system. For this reason, the default setting (1) is
recommended for most systems and applications.
The number of packets that are sent before an
interrupt is generated (assuming that the
recv_ticks timer does not expire first).
Default: 32 (packets)
Minimum: 0
Maximum: 511
The receive DMA burst size (in longwords) for the
DEGPA Gigabit Ethernet card. The default value (0)
specifies that the receive DMA burst size is set to
be the maximum supported by the Gigabit Ethernet
card.
Although this attribute can be modified at run
time, do not change it unless instructed to do so
by support personnel or patch kit instructions.
The number of microseconds (usec) between the
receipt of the last packet and the generation of an
interrupt (assuming that the recv_coal threshold is
not reached first).
Default: 200 (usec)
Minimum: 0
Maximum: 888,888
The number of packets that are sent before an
interrupt is generated (assuming that the
send_ticks timer does not expire first).
Default: 32 (packets)
Minimum: 0
Maximum: 511
The number of microseconds (usec) between the
transmission of the last packet and the generation
of an interrupt (assuming that the send_coal
threshold is not reached first).
Default: 200 (usec)
Minimum: 0
Maximum: 888,888
The number of microseconds (usec) between statistics
updates from the adapter to the host.
Default: 1000000 (usec), or 1 second
Minimum: 1
Maximum: 10000000
The transmit DMA burst size (in longwords) for the
DEGPA Gigabit Ethernet card. The default value (0)
specifies that the transmit DMA burst size is set
to be the maximum supported by the Gigabit Ethernet
card.
Although this attribute can be modified at run
time, do not change it unless instructed to do so
by support personnel or patch kit instructions.
sys_attrs(5)
sys_attrs_alt(5)
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