IFLIB(4)

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.

simple_tx
    When set to one, iflib uses a simple transmit routine with no queuing at all. By default, iflib uses a highly optimized, lockless, transmit queue called mp_ring. This performs well when there are more CPU cores than NIC queues and prevents lock contention for transmit resources. Unfortunately, mp_ring incurs unneeded overheads on workloads where resource contention is not a problem (well behaved applications on systems where there are as many NIC queues as CPU cores). Note that when this is enabled, the tx_abdicate sysctl is no longer applicable and is ignored. Defaults to zero.

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.

tx_defer_mfree
    Controls the threshold in packets before iflib will free the memory (mbufs) for the packets that it has transmitted. When this is nonzero, mbufs will be freed outside the transmit lock. Setting this can reduce lock contention and CPU use when using simple_tx. Note that this applies only when simple_tx is enabled.

tx_reclaim_thresh
    Controls the threshold in packets before iflib will ask the driver how many transmitted packets can be reclaimed. Determining how many many packets can be reclaimed can be expensive on some drivers.

tx_reclaim_ticks
    Controls the time in ticks before iflib will ask the driver how many transmitted packets can be reclaimed. Determining how many many packets can be reclaimed can be expensive on some drivers.

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 provides 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.