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sys_attrs_bcm(5)
NAME
sys_attrs_bcm - bcm subsystem attributes
DESCRIPTION
This reference page lists and describes attributes for the bcm (bcm) kernel
subsystem. This subsystem is used by the DEGXA Gigabit Ethernet Network
Interface Cards (NICs). The hardware and firmware for these adapters
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_frames and *_coal_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.
DriverTimeStamp
The date and time when the driver was last built. For example, May 24
2002 09:22:47. This is a read-only attribute and cannot be changed.
DriverVersion
The version number of the bcm driver. This is a read-only attribute,
and cannot be changed.
minimal_isr
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 DEGXA 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
Gigabit Ethernet cards.
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
DEGXA Gigabit Ethernet card supported by the system. For this reason,
the default setting (1) is recommended for most systems and
applications.
This attribute can be modified at run time.
jumbo_max
The maximum number of jumbo (9000 byte) receive buffers to allocate if
jumbo frames are enabled.
Default: 255 (buffers)
Minimum: 1
Maximum: 255
This attribute can be modified at run time.
* rx_coal_frames
The number of packets that are received before an interrupt is
generated (assuming that the rx_coal_ticks timer does not expire
first).
Default: 10 (packets)
Minimum: 0
Maximum: 1023
This attribute can be modified at run time.
* rx_coal_frames_int
The number of packets that are received before a new status block is
sent to the host through a direct memory access (DMA) transfer while
the driver is servicing an interrupt (assuming that the
rx_coal_ticks_int timer does not expire first).
Default: 4 (packets)
Minimum: 0
Maximum: 1023
This attribute can be modified at run time.
* rx_coal_ticks
The number of microseconds (usec) that elapse after receipt of the last
packet before an interrupt is generated (assuming that the
rx_coal_frames threshold is not reached first).
Default: 150 (usec)
Minimum: 0
Maximum: INT_MAX, or 2 billion
This attribute can be modified at run time.
* rx_coal_ticks_int
The number of microseconds (usec) that elapse after receipt of the last
packet before a new status block is sent to the host through a direct
memory access (DMA) transfer while the driver is servicing an interrupt
(assuming that the rx_coal_frames_int threshold is not reached first).
Default: 50 (usec)
Minimum: 0
Maximum: INT_MAX, or 2 billion
This attribute can be modified at run time.
standard_max
The maximum number of standard (1500 byte) receive buffers to allocate.
Default: 511 (buffers)
Minimum: 1
Maximum: 511
This attribute can be modified at run time.
stats_coal_ticks
The number of microseconds (usec) that elapse between statistics
updates from the adapter to the host.
Default: 1000000 (usec), or 1 second
Minimum: 0
Maximum: INT_MAX, or 2 billion
This attribute can be modified at run time.
* tx_coal_frames
The number of packets that are sent before an interrupt is generated
(assuming that the tx_coal_ticks timer does not expire first).
Default: 10 (packets)
Minimum: 0
Maximum: 511
This attribute can be modified at run time.
* tx_coal_frames_int
The number of packets that are sent before an interrupt is generated
(assuming that the tx_coal_ticks_int timer does not expire first).
Default: 4 (packets)
Minimum: 0
Maximum: 511
This attribute can be modified at run time.
* tx_coal_ticks
The number of microseconds (usec) that elapse after transmission of the
last packet before an interrupt is generated (assuming that the
tx_coal_frames threshold is not reached first).
Default: 150 (usec)
Minimum: 0
Maximum: INT_MAX, or 2 billion
This attribute can be modified at run time.
* tx_coal_ticks_int
The number of microseconds (usec) that elapse after transmission of the
last packet before an interrupt is generated (assuming that the
tx_coal_frames_int threshold is not reached first).
Default: 50 (usec)
Minimum: 0
Maximum: INT_MAX, or 2 billion
This attribute can be modified at run time.
use_tx_thread
The value that defines how to use the transmit thread to process
transmissions.
Default: 1
Minimum: 0
Maximum: 3
This attribute can be modified at run time.
Permitted values and their meaning are as follows:
0 Do not awaken the transmit thread. Transmits are started in line by
the thread calling the bcm_start routine. Transmit completions will
occur in the same thread as receive completions.
1 Awakens the transmit thread to start transmits. This allows a
quick return from the bcm_start routine.
2 Awakens the transmit thread to complete transmits concurrently with
receive completions.
3 Awakens the transmit thread according values 1 and 2.
SEE ALSO
sys_attrs(5)
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