a90b5eb0c8
The new manpage documents the tunables and statistic sysctls exposed by iflib. Reviewed by: bcr Approved by: re (gjb) Sponsored by: Limelight Networks Differential Revision: https://reviews.freebsd.org/D16920
196 lines
7.0 KiB
Groff
196 lines
7.0 KiB
Groff
.\" $FreeBSD$
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.Dd September 20, 2018
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.Dt IFLIB 4
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.Os
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.Sh NAME
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.Nm iflib
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.Nd Network Interface Driver Framework
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.Sh SYNOPSIS
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.Cd "device pci"
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.Cd "device iflib"
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.Sh DESCRIPTION
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.Nm
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is a framework for network interface drivers for
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.Fx .
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It is designed to remove a large amount of the boilerplate that is often
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needed for modern network interface devices, allowing driver authors to
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focus on the specific code needed for their hardware.
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This allows for a shared set of
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.Xr sysctl 8
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names, rather than each driver naming them individually.
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.Sh SYSCTL VARIABLES
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These variables must be set before loading the driver, either via
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.Xr loader.conf 5
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or through the use of
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.Xr kenv 1 .
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They are all prefixed by
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.Va dev.X.Y.iflib.
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where X is the driver name, and Y is the instance number.
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.Bl -tag -width indent
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.It Va override_nrxds
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Override the number of RX descriptors for each queue.
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The value is a comma separated list of positive integers.
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Some drivers only use a single value, but others may use more.
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These numbers must be powers of two, and zero means to use the default.
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Individual drivers may have additional restrictions on allowable values.
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Defaults to all zeros.
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.It Va override_ntxds
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Override the number of TX descriptors for each queue.
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The value is a comma separated list of positive integers.
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Some drivers only use a single value, but others may use more.
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These numbers must be powers of two, and zero means to use the default.
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Individual drivers may have additional restrictions on allowable values.
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Defaults to all zeros.
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.It Va override_qs_enable
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When set, allows the number of transmit and receive queues to be different.
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If not set, the lower of the number of TX or RX queues will be used for both.
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.It Va override_nrxqs
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Set the number of RX queues.
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If zero, the number of RX queues is derived from the number of cores on the
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socket connected to the controller.
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Defaults to 0.
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.It Va override_ntxqs
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Set the number of TX queues.
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If zero, the number of TX queues is derived from the number of cores on the
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socket connected to the controller.
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.It Va disable_msix
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Disables MSI-X interrupts for the device.
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.El
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.Pp
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These
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.Xr sysctl 8
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variables can be changed at any time:
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.Bl -tag -width indent
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.It Va tx_abdicate
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Controls how the transmit ring is serviced.
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If set to zero, when a frame is submitted to the transmission ring, the same
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task that is submitting it will service the ring unless there's already a
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task servicing the TX ring.
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This ensures that whenever there is a pending transmission,
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the transmit ring is being serviced.
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This results in higher transmit throughput.
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If set to a non-zero value, task returns immediately and the transmit
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ring is serviced by a different task.
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This returns control to the caller faster and under high receive load,
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may result in fewer dropped RX frames.
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.It Va rx_budget
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Sets the maximum number of frames to be received at a time.
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Zero (the default) indicates the default (currently 16) should be used.
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.El
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.Pp
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There are also some global sysctls which can change behaviour for all drivers,
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and may be changed at any time.
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.Bl -tag -width indent
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.It Va net.iflib.min_tx_latency
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If this is set to a non-zero value, iflib will avoid any attempt to combine
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multiple transmits, and notify the hardware as quickly as possible of
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new descriptors.
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This will lower the maximum throughput, but will also lower transmit latency.
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.It Va net.iflib.no_tx_batch
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Some NICs allow processing completed transmit descriptors in batches.
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Doing so usually increases the transmit throughput by reducing the number of
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transmit interrupts.
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Setting this to a non-zero value will disable the use of this feature.
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.El
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.Pp
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These
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.Xr sysctl 8
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variables are read-only:
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.Bl -tag -width indent
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.It Va driver_version
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A string indicating the internal version of the driver.
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.El
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.Pp
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There are a number of queue state
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.Xr sysctl 8
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variables as well:
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.Bl -tag -width indent
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.It Va txqZ
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The following are repeated for each transmit queue, where Z is the transmit
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queue instance number:
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.Bl -tag -width indent
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.It Va r_abdications
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Number of consumer abdications in the MP ring for this queue.
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An abdication occurs on every ring submission when tx_abdicate is true.
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.It Va r_restarts
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Number of consumer restarts in the MP ring for this queue.
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A restart occurs when an attempt to drain a non-empty ring fails,
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and the ring is already in the STALLED state.
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.It Va r_stalls
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Number of consumer stalls in the MP ring for this queue.
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A stall occurs when an attempt to drain a non-empty ring fails.
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.It Va r_starts
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Number of normal consumer starts in the MP ring for this queue.
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A start occurs when the MP ring transitions from IDLE to BUSY.
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.It Va r_drops
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Number of drops in the MP ring for this queue.
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A drop occurs when there is an attempt to add an entry to an MP ring with
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no available space.
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.It Va r_enqueues
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Number of entries which have been enqueued to the MP ring for this queue.
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.It Va ring_state
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MP (soft) ring state.
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This privides a snapshot of the current MP ring state, including the producer
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head and tail indexes, the consumer index, and the state.
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The state is one of "IDLE", "BUSY",
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"STALLED", or "ABDICATED".
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.It Va txq_cleaned
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The number of transmit descriptors which have been reclaimed.
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Total cleaned.
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.It Va txq_processed
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The number of transmit descriptors which have been processed, but may not yet
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have been reclaimed.
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.It Va txq_in_use
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Descriptors which have been added to the transmit queue,
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but have not yet been cleaned.
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This value will include both untransmitted descriptors as well as descriptors
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which have been processed.
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.It Va txq_cidx_processed
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The transmit queue consumer index of the next descriptor to process.
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.It Va txq_cidx
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The transmit queue consumer index of the oldest descriptor to reclaim.
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.It Va txq_pidx
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The transmit queue producer index where the next descriptor to transmit will
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be inserted.
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.It Va no_tx_dma_setup
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Number of times DMA mapping a transmit mbuf failed for reasons other than EFBIG.
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.It Va txd_encap_efbig
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Number of times DMA mapping a transmit mbuf failed due to requiring too many
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segments.
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.It Va tx_map_failed
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Number of times DMA mapping a transmit mbuf failed for any reason
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(sum of no_tx_dma_setup and txd_encap_efbig)
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.It Va no_desc_avail
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Number of times a descriptor couldn't be added to the transmit ring because
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the transmit ring was full.
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.It Va mbuf_defrag_failed
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Number of times both
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.Xr m_collapse 9
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and
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.Xr m_defrag 9
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failed after an EFBIG error
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result from DMA mapping a transmit mbuf.
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.It Va m_pullups
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Number of times m_pullup was called attempting to parse a header.
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.It Va mbuf_defrag
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Number of times m_defrag was called.
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.El
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.It Va rxqZ
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The following are repeated for each receive queue, where Z is the
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receive queue instance number:
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.Bl -tag -width indent
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.It Va rxq_fl0.credits
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Credits currently available in the receive ring.
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.It Va rxq_fl0.cidx
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Current receive ring consumer index.
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.It Va rxq_fl0.pidx
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Current receive ring producer index.
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.El
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.El
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Additional OIDs useful for driver and iflib development are exposed when the
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INVARIANTS and/or WITNESS options are enabled in the kernel.
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.Sh SEE ALSO
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.Xr iflib 9
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.Sh HISTORY
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This framework was introduced in 11.0.
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