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30 .\" nvme driver man page.
32 .\" Author: Jim Harris <jimharris@FreeBSD.org>
41 .Nd NVM Express core driver
43 To compile this driver into your kernel,
44 place the following line in your kernel configuration file:
45 .Bd -ragged -offset indent
49 Or, to load the driver as a module at boot, place the following line in
51 .Bd -literal -offset indent
55 Most users will also want to enable
57 to surface NVM Express namespaces as disk devices.
58 Note that in NVM Express terms, a namespace is roughly equivalent to a
63 driver provides support for NVM Express (NVMe) controllers, such as:
66 Hardware initialization
68 Per-CPU IO queue pairs
70 API for registering NVMe namespace consumers such as
73 API for submitting NVM commands to namespaces
75 Ioctls for controller and namespace configuration and management
78 creates controller devices in the format
80 and namespace devices in
83 Note that the NVM Express specification starts numbering namespaces at 1,
84 not 0, and this driver follows that convention.
89 will create an I/O queue pair for each CPU, provided enough MSI-X vectors
91 To force a single I/O queue pair shared by all CPUs, set the following
94 .Bd -literal -offset indent
95 hw.nvme.per_cpu_io_queues=0
98 To force legacy interrupts for all
100 driver instances, set the following tunable value in
102 .Bd -literal -offset indent
106 Note that use of INTx implies disabling of per-CPU I/O queue pairs.
108 The following controller-level sysctls are currently implemented:
109 .Bl -tag -width indent
110 .It Va dev.nvme.0.int_coal_time
111 (R/W) Interrupt coalescing timer period in microseconds.
113 .It Va dev.nvme.0.int_coal_threshold
114 (R/W) Interrupt coalescing threshold in number of command completions.
118 The following queue pair-level sysctls are currently implemented.
119 Admin queue sysctls take the format of dev.nvme.0.adminq and I/O queue sysctls
120 take the format of dev.nvme.0.ioq0.
121 .Bl -tag -width indent
122 .It Va dev.nvme.0.ioq0.num_entries
123 (R) Number of entries in this queue pair's command and completion queue.
124 .It Va dev.nvme.0.ioq0.num_tr
125 (R) Number of nvme_tracker structures currently allocated for this queue pair.
126 .It Va dev.nvme.0.ioq0.num_prp_list
127 (R) Number of nvme_prp_list structures currently allocated for this queue pair.
128 .It Va dev.nvme.0.ioq0.sq_head
129 (R) Current location of the submission queue head pointer as observed by
131 The head pointer is incremented by the controller as it takes commands off
132 of the submission queue.
133 .It Va dev.nvme.0.ioq0.sq_tail
134 (R) Current location of the submission queue tail pointer as observed by
136 The driver increments the tail pointer after writing a command
137 into the submission queue to signal that a new command is ready to be
139 .It Va dev.nvme.0.ioq0.cq_head
140 (R) Current location of the completion queue head pointer as observed by
142 The driver increments the head pointer after finishing
143 with a completion entry that was posted by the controller.
144 .It Va dev.nvme.0.ioq0.num_cmds
145 (R) Number of commands that have been submitted on this queue pair.
146 .It Va dev.nvme.0.ioq0.dump_debug
147 (W) Writing 1 to this sysctl will dump the full contents of the submission
148 and completion queues to the console.
158 driver first appeared in
164 driver was developed by Intel and originally written by
165 .An Jim Harris Aq jimharris@FreeBSD.org ,
166 with contributions from Joe Golio at EMC.
168 This man page was written by
169 .An Jim Harris Aq jimharris@FreeBSD.org .