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 expose NVM Express namespaces as disk devices which can be
       partitioned.  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

       The nvme driver creates controller device nodes in the format /dev/nvmeX and namespace  device  nodes  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 and NVMe queue
       pairs can be allocated.  If not enough vectors or queue pairs are available, nvme(4) will use  a  smaller
       number of queue pairs and assign multiple CPUs per queue pair.

       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  assign more than one CPU per I/O queue pair, thereby reducing the number of MSI-X vectors consumed by
       the device, set the following tunable value in loader.conf(5):

             hw.nvme.min_cpus_per_ioq=X

       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.num_cpus_per_ioq
               (R) Number of CPUs associated with each I/O queue pair.

       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>.

Debian                                           January 7, 2016                                         NVME(4)