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NAME
iflib — Network Interface Driver Framework
SYNOPSIS
device pci
device iflib
DESCRIPTION
iflib is a framework for network interface drivers for FreeBSD. It is designed to remove a large amount
of the boilerplate that is often needed for modern network interface devices, allowing driver authors to
focus on the specific code needed for their hardware. This allows for a shared set of sysctl(8) names,
rather than each driver naming them individually.
SYSCTL VARIABLES
These variables must be set before loading the driver, either via loader.conf(5) or through the use of
kenv(1). They are all prefixed by dev.X.Y.iflib. where X is the driver name, and Y is the instance
number.
override_nrxds
Override the number of RX descriptors for each queue. The value is a comma separated list of
positive integers. Some drivers only use a single value, but others may use more. These numbers
must be powers of two, and zero means to use the default. Individual drivers may have additional
restrictions on allowable values. Defaults to all zeros.
override_ntxds
Override the number of TX descriptors for each queue. The value is a comma separated list of
positive integers. Some drivers only use a single value, but others may use more. These numbers
must be powers of two, and zero means to use the default. Individual drivers may have additional
restrictions on allowable values. Defaults to all zeros.
override_qs_enable
When set, allows the number of transmit and receive queues to be different. If not set, the
lower of the number of TX or RX queues will be used for both.
override_nrxqs
Set the number of RX queues. If zero, the number of RX queues is derived from the number of
cores on the socket connected to the controller. Defaults to 0.
override_ntxqs
Set the number of TX queues. If zero, the number of TX queues is derived from the number of
cores on the socket connected to the controller.
disable_msix
Disables MSI-X interrupts for the device.
core_offset
Specifies a starting core offset to assign queues to. If the value is unspecified or 65535,
cores are assigned sequentially across controllers.
separate_txrx
Requests that RX and TX queues not be paired on the same core. If this is zero or not set, an RX
and TX queue pair will be assigned to each core. When set to a non-zero value, TX queues are
assigned to cores following the last RX queue.
These sysctl(8) variables can be changed at any time:
tx_abdicate
Controls how the transmit ring is serviced. If set to zero, when a frame is submitted to the
transmission ring, the same task that is submitting it will service the ring unless there's
already a task servicing the TX ring. This ensures that whenever there is a pending
transmission, the transmit ring is being serviced. This results in higher transmit throughput.
If set to a non-zero value, task returns immediately and the transmit ring is serviced by a
different task. This returns control to the caller faster and under high receive load, may
result in fewer dropped RX frames.
rx_budget
Sets the maximum number of frames to be received at a time. Zero (the default) indicates the
default (currently 16) should be used.
There are also some global sysctls which can change behaviour for all drivers, and may be changed at any
time.
net.iflib.min_tx_latency
If this is set to a non-zero value, iflib will avoid any attempt to combine multiple transmits,
and notify the hardware as quickly as possible of new descriptors. This will lower the maximum
throughput, but will also lower transmit latency.
net.iflib.no_tx_batch
Some NICs allow processing completed transmit descriptors in batches. Doing so usually increases
the transmit throughput by reducing the number of transmit interrupts. Setting this to a non-
zero value will disable the use of this feature.
These sysctl(8) variables are read-only:
driver_version
A string indicating the internal version of the driver.
There are a number of queue state sysctl(8) variables as well:
txqZ The following are repeated for each transmit queue, where Z is the transmit queue instance
number:
r_abdications
Number of consumer abdications in the MP ring for this queue. An abdication occurs on
every ring submission when tx_abdicate is true.
r_restarts
Number of consumer restarts in the MP ring for this queue. A restart occurs when an
attempt to drain a non-empty ring fails, and the ring is already in the STALLED state.
r_stalls
Number of consumer stalls in the MP ring for this queue. A stall occurs when an attempt
to drain a non-empty ring fails.
r_starts
Number of normal consumer starts in the MP ring for this queue. A start occurs when the
MP ring transitions from IDLE to BUSY.
r_drops
Number of drops in the MP ring for this queue. A drop occurs when there is an attempt to
add an entry to an MP ring with no available space.
r_enqueues
Number of entries which have been enqueued to the MP ring for this queue.
ring_state
MP (soft) ring state. This privides a snapshot of the current MP ring state, including
the producer head and tail indexes, the consumer index, and the state. The state is one
of "IDLE", "BUSY", "STALLED", or "ABDICATED".
txq_cleaned
The number of transmit descriptors which have been reclaimed. Total cleaned.
txq_processed
The number of transmit descriptors which have been processed, but may not yet have been
reclaimed.
txq_in_use
Descriptors which have been added to the transmit queue, but have not yet been cleaned.
This value will include both untransmitted descriptors as well as descriptors which have
been processed.
txq_cidx_processed
The transmit queue consumer index of the next descriptor to process.
txq_cidx
The transmit queue consumer index of the oldest descriptor to reclaim.
txq_pidx
The transmit queue producer index where the next descriptor to transmit will be inserted.
no_tx_dma_setup
Number of times DMA mapping a transmit mbuf failed for reasons other than EFBIG.
txd_encap_efbig
Number of times DMA mapping a transmit mbuf failed due to requiring too many segments.
tx_map_failed
Number of times DMA mapping a transmit mbuf failed for any reason (sum of no_tx_dma_setup
and txd_encap_efbig)
no_desc_avail
Number of times a descriptor couldn't be added to the transmit ring because the transmit
ring was full.
mbuf_defrag_failed
Number of times both m_collapse(9) and m_defrag(9) failed after an EFBIG error result
from DMA mapping a transmit mbuf.
m_pullups
Number of times m_pullup(9) was called attempting to parse a header.
mbuf_defrag
Number of times m_defrag(9) was called.
rxqZ The following are repeated for each receive queue, where Z is the receive queue instance number:
rxq_fl0.credits
Credits currently available in the receive ring.
rxq_fl0.cidx
Current receive ring consumer index.
rxq_fl0.pidx
Current receive ring producer index.
Additional OIDs useful for driver and iflib development are exposed when the INVARIANTS and/or WITNESS
options are enabled in the kernel.
SEE ALSO
iflib(9)
HISTORY
This framework was introduced in FreeBSD 11.0.
Debian September 27, 2018 IFLIB(4)