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NAME
     nvme — NVM Express core driver


SYNOPSIS
     To compile this driver into your kernel, place the following line in your
     kernel configuration file:

           device nvme

     Or, to load the driver as a module at boot, place the following line in
     loader.conf(5):

           nvme_load="YES"

     Most users will also want to enable nvd(4) to surface NVM Express
     namespaces as disk devices.  Note that in NVM Express terms, a namespace
     is roughly equivalent to a SCSI LUN.


DESCRIPTION
     The nvme driver provides support for NVM Express (NVMe) controllers, such
     as:

     ·   Hardware initialization

     ·   Per-CPU IO queue pairs

     ·   API for registering NVMe namespace consumers such as nvd(4)

     ·   API for submitting NVM commands to namespaces

     ·   Ioctls for controller and namespace configuration and management nvme
         creates controller devices in the format /dev/nvmeX and namespace
         devices in the format /dev/nvmeXnsY.  Note that the NVM Express
         specification starts numbering namespaces at 1, not 0, and this
         driver follows that convention.


CONFIGURATION
     By default, nvme will create an I/O queue pair for each CPU, provided
     enough MSI-X vectors can be allocated.  To force a single I/O queue pair
     shared by all CPUs, set the following tunable value in loader.conf(5):

           hw.nvme.per_cpu_io_queues=0

     To force legacy interrupts for all nvme driver instances, set the
     following tunable value in loader.conf(5):

           hw.nvme.force_intx=1

     Note that use of INTx implies disabling of per-CPU I/O queue pairs.


SYSCTL VARIABLES
     The following controller-level sysctls are currently implemented:

     dev.nvme.0.int_coal_time
             (R/W) Interrupt coalescing timer period in microseconds.  Set to
             0 to disable.

     dev.nvme.0.int_coal_threshold
             (R/W) Interrupt coalescing threshold in number of command
             completions.  Set to 0 to disable.

     The following queue pair-level sysctls are currently implemented.  Admin
     queue sysctls take the format of dev.nvme.0.adminq and I/O queue sysctls
     take the format of dev.nvme.0.ioq0.

     dev.nvme.0.ioq0.num_entries
             (R) Number of entries in this queue pair's command and completion
             queue.

     dev.nvme.0.ioq0.num_tr
             (R) Number of nvme_tracker structures currently allocated for
             this queue pair.

     dev.nvme.0.ioq0.num_prp_list
             (R) Number of nvme_prp_list structures currently allocated for
             this queue pair.

     dev.nvme.0.ioq0.sq_head
             (R) Current location of the submission queue head pointer as
             observed by the driver.  The head pointer is incremented by the
             controller as it takes commands off of the submission queue.

     dev.nvme.0.ioq0.sq_tail
             (R) Current location of the submission queue tail pointer as
             observed by the driver.  The driver increments the tail pointer
             after writing a command into the submission queue to signal that
             a new command is ready to be processed.

     dev.nvme.0.ioq0.cq_head
             (R) Current location of the completion queue head pointer as
             observed by the driver.  The driver increments the head pointer
             after finishing with a completion entry that was posted by the
             controller.

     dev.nvme.0.ioq0.num_cmds
             (R) Number of commands that have been submitted on this queue
             pair.

     dev.nvme.0.ioq0.dump_debug
             (W) Writing 1 to this sysctl will dump the full contents of the
             submission and completion queues to the console.


SEE ALSO
     nvd(4), pci(4), nvmecontrol(8), disk(9).


HISTORY
     The nvme driver first appeared in FreeBSD 9.2.


AUTHORS
     The nvme driver was developed by Intel and originally written by Jim
     Harris ⟨jimharris@FreeBSD.org⟩, with contributions from Joe Golio at EMC.

     This man page was written by Jim Harris ⟨jimharris@FreeBSD.org⟩.