Tunables can be set at the loader(8) prompt before booting the kernel or stored in loader.conf(5).
hw.cxgbe.ntxq
Number of tx queues used for a port. The default is 16 or the number of CPU cores in the system,
whichever is less.
hw.cxgbe.nrxq
Number of rx queues used for a port. The default is 8 or the number of CPU cores in the system,
whichever is less.
hw.cxgbe.holdoff_timer_idx
Timer index value used to delay interrupts. The holdoff timer list has the values 1, 5, 10, 50,
100, and 200 by default (all values are in microseconds) and the index selects a value from this
list. The default value is 1 which means the timer value is 5us. Different interfaces can be
assigned different values at any time via the dev.<port>.X.holdoff_tmr_idx sysctl.
hw.cxgbe.holdoff_pktc_idx
Packet-count index value used to delay interrupts. The packet-count list has the values 1, 8,
16, and 32 by default, and the index selects a value from this list. The default value is -1
which means packet counting is disabled and interrupts are generated based solely on the holdoff
timer value. Different interfaces can be assigned different values via the
dev.<port>.X.holdoff_pktc_idx sysctl. This sysctl works only when the interface has never been
marked up (as done by ifconfig up).
hw.cxgbe.qsize_txq
Number of entries in a transmit queue's descriptor ring. A buf_ring of the same size is also
allocated for additional software queuing. See ifnet(9). The default value is 1024. Different
interfaces can be assigned different values via the dev.<port>.X.qsize_txq sysctl. This sysctl
works only when the interface has never been marked up (as done by ifconfig up).
hw.cxgbe.qsize_rxq
Number of entries in a receive queue's descriptor ring. The default value is 1024. Different
interfaces can be assigned different values via the dev.<port>.X.qsize_rxq sysctl. This sysctl
works only when the interface has never been marked up (as done by ifconfig up).
hw.cxgbe.interrupt_types
Permitted interrupt types. Bit 0 represents INTx (line interrupts), bit 1 MSI, and bit 2 MSI-X.
The default is 7 (all allowed). The driver selects the best possible type out of the allowed
types. Note that Virtual Functions do not support INTx interrupts and fail to attach if neither
MSI nor MSI-X are enabled.
hw.cxgbe.fl_pktshift
Number of padding bytes inserted before the beginning of an Ethernet frame in the receive buffer.
The default value of 2 ensures that the Ethernet payload (usually the IP header) is at a 4 byte
aligned address. 0-7 are all valid values.
hw.cxgbe.fl_pad
A non-zero value ensures that writes from the hardware to a receive buffer are padded up to the
specified boundary. The default is -1 which lets the driver pick a pad boundary. 0 disables
trailer padding completely.
hw.cxgbe.buffer_packing
Allow the hardware to deliver multiple frames in the same receive buffer opportunistically. The
default is -1 which lets the driver decide. 0 or 1 explicitly disable or enable this feature.
hw.cxgbe.allow_mbufs_in_cluster
1 allows the driver to lay down one or more mbufs within the receive buffer opportunistically.
This is the default. 0 prohibits the driver from doing so.
hw.cxgbe.largest_rx_clusterhw.cxgbe.safest_rx_cluster
Sizes of rx clusters. Each of these must be set to one of the sizes available (usually 2048,
4096, 9216, and 16384) and largest_rx_cluster must be greater than or equal to safest_rx_cluster.
The defaults are 16384 and 4096 respectively. The driver never attempts to allocate a receive
buffer larger than largest_rx_cluster and falls back to allocating buffers of safest_rx_cluster
size if an allocation larger than safest_rx_cluster fails. Note that largest_rx_cluster merely
establishes a ceiling -- the driver is allowed to allocate buffers of smaller sizes.
Certain settings and resources for Virtual Functions are dictated by the parent Physical Function driver.
For example, the Physical Function driver limits the number of queues available to a Virtual Function.
Some of these limits can be adjusted in the firmware configuration file used with the Physical Function
driver.
The PAUSE settings on the port of a Virtual Function are inherited from the settings of the same port on
the Physical Function. Virtual Functions cannot modify the setting and track changes made to the
associated port's setting by the Physical Function driver.
Receive queues on a Virtual Function always drop packets in response to congestion (equivalent to setting
hw.cxgbe.cong_drop to 1).
The VF driver currently depends on the PF driver. As a result, loading the VF driver also loads the PF
driver as a dependency.
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